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Discussion Starter #1
Replaced wire harness after going into "limp mode". Prior to replacing harness, engine would fire with starting fluid...now it won't. This is a 16 pin DM style 124.092 .

To determine if the ECU / OVP is functional, can I check the ECU(at connector 1 {interior side} to determine if getting power from OVP by checking voltage at pin 27(Voltage supply (circuit 87M)??? Would this prevent the engine from starting or does it only control the idle and cold start issues?

I'm trying to avoid throwing parts at it and would like to know how one determines a "fried" ECU from the bad harness shorting out the ECU prior to my changing out the wire harness. I also replaced the Crank sensor and I show a code fault from DM pin 8 using the code reader which has 24 blinks. I bought a $25 one off ebay trying to save some money. The Dm module pin 3 doesn't blink after checking with code reader or depressing the red led button...no blinks at all.

I'll do my profile after this which is my first post after reading all the threads on crank no start. You have a great forum and thanks.
 

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As a 1995, you have an M104 with the HFM fuel system. Pin 3 on the DM is used for the earlier CIS fuel system so it is no surprise that you see nothing there (unless you have a California car). 24 blinks on pin 8 is the code for, "CKP sensor or magnet for position sensor not recognized". which would certainly explain the carnk, no-start issue. The very fact that you are seeing a stored error code tells me that the OVP is probably okay. Check Fuse 7 and check for +12 on pin 16 of the DM (this power supplied via the OVP) for good measure. Check the connection to your new CKP to make sure it is okay. Make sure it is mechanically installed correctly.
 

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Discussion Starter #3
As a 1995, you have an M104 with the HFM fuel system. Pin 3 on the DM is used for the earlier CIS fuel system so it is no surprise that you see nothing there (unless you have a California car). 24 blinks on pin 8 is the code for, "CKP sensor or magnet for position sensor not recognized". which would certainly explain the carnk, no-start issue. The very fact that you are seeing a stored error code tells me that the OVP is probably okay. Check Fuse 7 and check for +12 on pin 16 of the DM (this power supplied via the OVP) for good measure. Check the connection to your new CKP to make sure it is okay. Make sure it is mechanically installed correctly.
Thanks for responding. I believe it is a Calif Car because it has the Red Led push button. It was working prior to the new wiring harness install. Now I press the Led button and get no light blink(shoud be one blink if all good} . I have a LED code reader that does work and cleared the codes that were left after removing the battery (many times). The only code I receive now is on pin 8 and the 24 blinks comes back when I clear them and then attempt at engine crank. That makes me think my ECU is still working. I ordered another "CKP" a few minutes ago from Ebay that is BOSH oem. It'l be here Wednesday. If the red led light on my 16 DM comes on...that implies I have connection to the ECU

Thanks for your time.
 

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Thanks for responding. I believe it is a Calif Car because it has the Red Led push button. It was working prior to the new wiring harness install. Now I press the Led button and get no light blink(shoud be one blink if all good} . I have a LED code reader that does work and cleared the codes that were left after removing the battery (many times). The only code I receive now is on pin 8 and the 24 blinks comes back when I clear them and then attempt at engine crank. That makes me think my ECU is still working. I ordered another "CKP" a few minutes ago from Ebay that is BOSH oem. It'l be here Wednesday. If the red led light on my 16 DM comes on...that implies I have connection to the ECU

Thanks for your time.
In case I wasn't clear, the red led on the DM16 pin comes on when I turn the ignition on...it just doesn't blink after I push the button for 4 sec. The code reader uses pin 1 (ground) pin 16 (+12 power) and the other plug for 8 and 14. It will not read pin 3 which is supposed to be a diagnostic code keeper. IF it is not seeing any diagnostic codes in pin 3, is the ECU still functioning??
 

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I think that Cali cars have a separate diagnostic module (DM) that drives that LED and pin 3 (I believe the requirement for the LED was a so called "OBDI" requirement). This module is powered via the OVP and via Fuse 9 (the memory backup power). The DM collects status information from the ECU and the CC/ICS via the CAN bus but does not control engine functions directly, so a lack of response from the DM does not necessarily mean the ECU is not functioning.
 

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I've done a lot of reading of your forum and thus the reason I joined. I'll post some pics of the wiring harness tomorrow while I'm waiting on the new CKP sensor. I'll say this, considering the shape it was in(anytime I moved any electrical wire I held my breath) I'm amazed it ran at all.

These are some of my electrical resources:

http://ww2.justanswer.com/uploads/eurotec/2011-01-08_180355_connector.pdf

file:///C:/Users/louis%20kral/AppData/Local/Packages/Microsoft.MicrosoftEdge_8wekyb3d8bbwe/TempState/Downloads/2018_10_26__mercedes_obd1_fault_codes_.pdf

The car was inherited. I've had it around for a couple of years. Ran good but started acting up on starting last month. Got the limp mode after attempting to start(which it did and smelled electrical burn and a little smoke at the end of the drive way. You'll see from the pictures the damage from the wires shorting and melting. Thank God no fire. I can understand why MB mechanics charge soooo much. The crank sensor is in the most inaccessible place they could have put it.

I hate electrical. I love mechanical. I'd rather tear an engine down than chase electrical issues. I'm sure I'll get my fill with this MB.
 

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Discussion Starter #7
I think that Cali cars have a separate diagnostic module (DM) that drives that LED and pin 3 (I believe the requirement for the LED was a so called "OBDI" requirement). This module is powered via the OVP and via Fuse 9 (the memory backup power). The DM collects status information from the ECU and the CC/ICS via the CAN bus but does not control engine functions directly, so a lack of response from the DM does not necessarily mean the ECU is not functioning.
Thanks for the reply. I'll see what the more pricey CKP sensor does. It's not rocket science to make a sensor with a magnet and a pin in it. I'll take a distributor and a carburetor and mechanical fuel pump any day.
 

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Replaced wire harness after going into "limp mode". Prior to replacing harness, engine would fire with starting fluid...now it won't. This is a 16 pin DM style 124.092 .

To determine if the ECU / OVP is functional, can I check the ECU(at connector 1 {interior side} to determine if getting power from OVP by checking voltage at pin 27(Voltage supply (circuit 87M)??? Would this prevent the engine from starting or does it only control the idle and cold start issues?

I'm trying to avoid throwing parts at it and would like to know how one determines a "fried" ECU from the bad harness shorting out the ECU prior to my changing out the wire harness. I also replaced the Crank sensor and I show a code fault from DM pin 8 using the code reader which has 24 blinks. I bought a $25 one off ebay trying to save some money. The Dm module pin 3 doesn't blink after checking with code reader or depressing the red led button...no blinks at all.

I'll do my profile after this which is my first post after reading all the threads on crank no start. You have a great forum and thanks.
[/QUOTE
.
A wiring harness replacement this late? You got lucky. The vast majority of the w124's burned up in the driveway years ago. Don't forget, the throttle body also has a rotted cable assembly too. Best to just replace the throttle body with new or rebuilt. Limp mode is caused mostly by a failed throttle body. Test the cruise control. If that doesn't work, your in Limp Mode for sure from a failed throttle body.
My 1995 w124/E320 had all the same problems you're describing. Rough or no idle period. Then no start when hot. The codes at pin 8 showed CKP sensor and MAF failure. Fuel pressure test and vacuum leak test checked out fine.
The CKP sensor was replaced first(ya what a nightmare that was) and things were a little better. The new MAF sensor then fixed the rest.
2 week later the hot start problem returned and left me stranded at the SuperMarket. No codes at pin 8. Now I'm thinking bad ECU.
So now it gets interesting. As a retired Electronics Engineer, I decided to remove and examine the ECU for possible leaking Electrolytic Capacitors. Deteriorated capacitors are everywhere in our lives. They don't last for ever. I changed out all 5 capacitors on the ECU. The engine has been running like never before(so far). Cold start doesn't rev as high, it idles like a purring cat, and even the engine running temperature is a little lower. The task I performed is out of reach for many people. It's a tedious task that requires professional equipment. Your local electronic repair shop might not help you because of liability issues. So you're faced with buying a new ECU or a rebuilt. Purchasing a used ECU still has old capacitors. Hope this helps.
 

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Discussion Starter #9
A wiring harness replacement this late? You got lucky. The vast majority of the w124's burned up in the driveway years ago. Don't forget, the throttle body also has a rotted cable assembly too. Best to just replace the throttle body with new or rebuilt. Limp mode is caused mostly by a failed throttle body. Test the cruise control. If that doesn't work, your in Limp Mode for sure from a failed throttle body.
My 1995 w124/E320 had all the same problems you're describing. Rough or no idle period. Then no start when hot. The codes at pin 8 showed CKP sensor and MAF failure. Fuel pressure test and vacuum leak test checked out fine.
The CKP sensor was replaced first(ya what a nightmare that was) and things were a little better. The new MAF sensor then fixed the rest.
2 week later the hot start problem returned and left me stranded at the SuperMarket. No codes at pin 8. Now I'm thinking bad ECU.
So now it gets interesting. As a retired Electronics Engineer, I decided to remove and examine the ECU for possible leaking Electrolytic Capacitors. Deteriorated capacitors are everywhere in our lives. They don't last for ever. I changed out all 5 capacitors on the ECU. The engine has been running like never before(so far). Cold start doesn't rev as high, it idles like a purring cat, and even the engine running temperature is a little lower. The task I performed is out of reach for many people. It's a tedious task that requires professional equipment. Your local electronic repair shop might not help you because of liability issues. So you're faced with buying a new ECU or a rebuilt. Purchasing a used ECU still has old capacitors. Hope this helps.
Thanks for the reply and information. Check out the pictures I'm fixing to post. I got the CKP remove/replace down to about 30 minutes.
 

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Discussion Starter #10
Here are the pictures of the wiring harness...the car was running quite well considering the shape it was in. I really couldn't service any electrical stuff and was careful when I did. The MAF is what fried and was insulated but brittle. The big burn in the harness was after the frying. I opened the harness connecter to see if the wires were brittle in there...and as you can see...they were...pre frying.

IMG_1387.JPG
IMG_1377.JPG
IMG_1378.JPG
IMG_1379.JPG
IMG_1380.JPG
IMG_1381.JPG
IMG_1376.JPG


And there you have it. Pretty amazing that the car ran considering all the electrical stool on a MB.
 

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Here are the pictures of the wiring harness...the car was running quite well considering the shape it was in. I really couldn't service any electrical stuff and was careful when I did. The MAF is what fried and was insulated but brittle. The big burn in the harness was after the frying. I opened the harness connecter to see if the wires were brittle in there...and as you can see...they were...pre frying.

View attachment 2604532 View attachment 2604535 View attachment 2604536 View attachment 2604537 View attachment 2604538 View attachment 2604539 View attachment 2604540

And there you have it. Pretty amazing that the car ran considering all the electrical stool on a MB.
Last time I saw a harness that bad it was after the fire! As for CKP and MAF sensors, the CKP is a cylinder shaped magnet with a coil. Since the Germans don't anticipate failure of anything, they put the CKP in the worst spot where it gets very hot. Magnets eventually lose strength from hi heat all the time. I bench tested mine and got a noticeable weaker signal than from the new one. The MAF is different. Power is sent from the ECU. The MAF has a micro circuit onboard that pre-processes and then sends a signal back to the ECU. I bench tested my failed MAF and got no response at all. The new MAF bench tested fine before I installed it. Just cleaning the old MAF is/was a waste of time. Mercedessource.com is helpful too.
 

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Discussion Starter #12
After putting the new "Bosch" CKP sensor in...still get the 24 blink code (CKP sensor or magnet for position sensor not recognized) and 30 blink code (Fuel pump relay module - open or short circuit) on pin 8...no other codes on pin 14... one blink.

What I want to know is this:

1) My diagnostic module "pin 3" does nothing...No one blink with code reader and no blink responses from the push button red LED which is on with key in on position. Does this mean the ECU is not functioning?

2) When I remove the ECT sensor from the thermostat housing (with key in on position) the cooling fans come on. That is # 28 on "engine"(2) wire harness to the ECU. It provides ground( ECT sensor ground).

http://ww2.justanswer.com/uploads/eurotec/2011-01-08_180355_connector.pdf

Does this imply that my ECU (engine wire harness side) is receiving signal from that sensor? It seems to me that it does. Ground is applied to the fan circuit(with key in on position) until the temperature sensor is triggered(open circuit) ...and the fans come on???
There are no pins with ECT designation that I see on the "compartment" side of the ECU. If I had a ground problem in my engine side ECU, wouldn't the fans come on when I turn the key on?

3) Are there any "simple " checks to see if my wiring harness is communicating with my ECU?

4) What is the best method to check continuity from the engine harness pins # 29 ( CKP sensor ground) and # 30( CKP sensor signal} and the sensor plug?

All thoughts/ideas welcome.
 

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Discussion Starter #13
A wiring harness replacement this late? You got lucky. The vast majority of the w124's burned up in the driveway years ago. Don't forget, the throttle body also has a rotted cable assembly too. Best to just replace the throttle body with new or rebuilt. Limp mode is caused mostly by a failed throttle body. Test the cruise control. If that doesn't work, your in Limp Mode for sure from a failed throttle body.
My 1995 w124/E320 had all the same problems you're describing. Rough or no idle period. Then no start when hot. The codes at pin 8 showed CKP sensor and MAF failure. Fuel pressure test and vacuum leak test checked out fine.
The CKP sensor was replaced first(ya what a nightmare that was) and things were a little better. The new MAF sensor then fixed the rest.
2 week later the hot start problem returned and left me stranded at the SuperMarket. No codes at pin 8. Now I'm thinking bad ECU.
So now it gets interesting. As a retired Electronics Engineer, I decided to remove and examine the ECU for possible leaking Electrolytic Capacitors. Deteriorated capacitors are everywhere in our lives. They don't last for ever. I changed out all 5 capacitors on the ECU. The engine has been running like never before(so far). Cold start doesn't rev as high, it idles like a purring cat, and even the engine running temperature is a little lower. The task I performed is out of reach for many people. It's a tedious task that requires professional equipment. Your local electronic repair shop might not help you because of liability issues. So you're faced with buying a new ECU or a rebuilt. Purchasing a used ECU still has old capacitors. Hope this helps.
I have tenacity but to much gorilla in me for tedious. I understand capacitors...work on my home AC. Never done circuit board work.
You need any MAD MONEY to fix mine???
If you know of any reputable rebuild companies, I'd appreciate any information you may have.

Thanks for your help.
 

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I have tenacity but to much gorilla in me for tedious. I understand capacitors...work on my home AC. Never done circuit board work.
You need any MAD MONEY to fix mine???
If you know of any reputable rebuild companies, I'd appreciate any information you may have.

Thanks for your help.
This is so weird. You're having the exact same problems that I'm having(had hopefully). I too got blink codes at pin 8 and nothing at pin 3. After each blink code you have 20 seconds to clear it. So hold the button for 8 seconds. Then continue on testing for more codes. Clear the code after each reading. Pin 8 and 14 will blink once when there are no codes. Once the codes are cleared start the car. It seems that no "Check Engine" light will happen unless there's a code at pin 3. So go back and check for codes at pin 8 and 14. If the codes return, there's a problem. You can check codes while the engine is running if you want but it will cause the Check Engine light to come on until you stop the engine then restart it.
If you have changed the engine harness there is really no need to do continuity checks back to the ECU connector.
1) MAF check; Take the connector off the MAF. Turn the key to on(but don't start the engine). Using a volt meter check for power from the ECU at pin 2 to gnd. Should be 10 to 12 volts. Turn the key off. Using an ohm meter check pins 4 and 5 to gnd. It should be a direct connect to battery gnd. Check pin 1(signal back to the ECU) to gnd. You should see resistance of some sort(not shorted to gnd and not an open).
2) CKP check; Unplug the connector and pull it into the engine area where you can get it. Key off. On that plug the center pin to gnd should see resistance of some sort. Again not shorted or an open condition. The outer ring on the plug should be a short to battery gnd.
3) Fuel Pump relay check; Easy bench test. The pinouts and circuit are drawn on the unit itself. Apply 12volts to the relay coil and listen for the click. Then make sure that the contacts work when you apply the 12volts!!! Leave the relay out. Look at the circuit diagram to see what 2 pins close to apply power to the pump. Go to the relay socket and short those 2 pins. This applies direct battery power to the pumps (no key necessary). Listen to the pumps. If they squeel, replace them. You will also hear the fuel pressure regulator bleeding the fuel return. It's a loud rattling noise but no worries.
As for an ECU check and rebuild, ecmoutlet.com are able to bench test any ECU so it seems. I would stipulate that you want the capacitors replaced on spec period.
You're getting a lot of views. I hope this is helping others too.
 

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This is so weird. You're having the exact same problems that I'm having(had hopefully). I too got blink codes at pin 8 and nothing at pin 3. After each blink code you have 20 seconds to clear it. So hold the button for 8 seconds. Then continue on testing for more codes. Clear the code after each reading. Pin 8 and 14 will blink once when there are no codes. Once the codes are cleared start the car. It seems that no "Check Engine" light will happen unless there's a code at pin 3. So go back and check for codes at pin 8 and 14. If the codes return, there's a problem. You can check codes while the engine is running if you want but it will cause the Check Engine light to come on until you stop the engine then restart it.
If you have changed the engine harness there is really no need to do continuity checks back to the ECU connector.
1) MAF check; Take the connector off the MAF. Turn the key to on(but don't start the engine). Using a volt meter check for power from the ECU at pin 2 to gnd. Should be 10 to 12 volts. Turn the key off. Using an ohm meter check pins 4 and 5 to gnd. It should be a direct connect to battery gnd. Check pin 1(signal back to the ECU) to gnd. You should see resistance of some sort(not shorted to gnd and not an open).
2) CKP check; Unplug the connector and pull it into the engine area where you can get it. Key off. On that plug the center pin to gnd should see resistance of some sort. Again not shorted or an open condition. The outer ring on the plug should be a short to battery gnd.
3) Fuel Pump relay check; Easy bench test. The pinouts and circuit are drawn on the unit itself. Apply 12volts to the relay coil and listen for the click. Then make sure that the contacts work when you apply the 12volts!!! Leave the relay out. Look at the circuit diagram to see what 2 pins close to apply power to the pump. Go to the relay socket and short those 2 pins. This applies direct battery power to the pumps (no key necessary). Listen to the pumps. If they squeel, replace them. You will also hear the fuel pressure regulator bleeding the fuel return. It's a loud rattling noise but no worries.
As for an ECU check and rebuild, ecmoutlet.com are able to bench test any ECU so it seems. I would stipulate that you want the capacitors replaced on spec period.
You're getting a lot of views. I hope this is helping others too.
I forgot to comment on the ECT. In most cars, if you disconnect the Thermostat Sensor the radiator fan will come on full power. Even with no key in the ignition. It sends a signal to the ECU telling it that an engine overheat condition has occurred. It's kind of a safety to stop a meltdown. My car will do the same thing if I up and disconnect the ECT. Scares the daylights out of you and you'll be thanking god that your hands weren't in the fan cowling.
 

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Discussion Starter #16
This is so weird. You're having the exact same problems that I'm having(had hopefully). I too got blink codes at pin 8 and nothing at pin 3. After each blink code you have 20 seconds to clear it. So hold the button for 8 seconds. Then continue on testing for more codes. Clear the code after each reading. Pin 8 and 14 will blink once when there are no codes. Once the codes are cleared start the car. It seems that no "Check Engine" light will happen unless there's a code at pin 3. So go back and check for codes at pin 8 and 14. If the codes return, there's a problem. You can check codes while the engine is running if you want but it will cause the Check Engine light to come on until you stop the engine then restart it.
If you have changed the engine harness there is really no need to do continuity checks back to the ECU connector.
1) MAF check; Take the connector off the MAF. Turn the key to on(but don't start the engine). Using a volt meter check for power from the ECU at pin 2 to gnd. Should be 10 to 12 volts. Turn the key off. Using an ohm meter check pins 4 and 5 to gnd. It should be a direct connect to battery gnd. Check pin 1(signal back to the ECU) to gnd. You should see resistance of some sort(not shorted to gnd and not an open).
2) CKP check; Unplug the connector and pull it into the engine area where you can get it. Key off. On that plug the center pin to gnd should see resistance of some sort. Again not shorted or an open condition. The outer ring on the plug should be a short to battery gnd.
3) Fuel Pump relay check; Easy bench test. The pinouts and circuit are drawn on the unit itself. Apply 12volts to the relay coil and listen for the click. Then make sure that the contacts work when you apply the 12volts!!! Leave the relay out. Look at the circuit diagram to see what 2 pins close to apply power to the pump. Go to the relay socket and short those 2 pins. This applies direct battery power to the pumps (no key necessary). Listen to the pumps. If they squeel, replace them. You will also hear the fuel pressure regulator bleeding the fuel return. It's a loud rattling noise but no worries.
As for an ECU check and rebuild, ecmoutlet.com are able to bench test any ECU so it seems. I would stipulate that you want the capacitors replaced on spec period.
You're getting a lot of views. I hope this is helping others too.
Once again thanks for the help.

The engine will not start(crank no start) due to the ECU not recognizing the CKP sensor(#24 code blink on hand held code reader) My in car diagnostic module (red LED light) lights up with key on but does not blink after pushing button. The hand held code blink reader keeps reading 24 and 30 after I clear the codes and then attempt to restart the engine. As long as the CKP sensor isn't recognized...I can't start the engine:

"
After each blink code you have 20 seconds to clear it. So hold the button for 8 seconds. Then continue on testing for more codes. Clear the code after each reading. Pin 8 and 14 will blink once when there are no codes. Once the codes are cleared start the car. It seems that no "Check Engine" light will happen unless there's a code at pin 3. So go back and check for codes at pin 8 and 14. If the codes return, there's a problem. You can check codes while the engine is running if you want but it will cause the Check Engine light to come on until you stop the engine then restart it.
If you have changed the engine harness there is really no need to do continuity checks back to the ECU connector."

"If you have changed the engine harness there is really no need to do continuity checks back to the ECU connector."

The continuity check would rule out a bad CKP plug wire on the "used" wiring harness I purchased...my reason for the continuity check For the ECU not to recognize the CKP sensor:
1) Bad Sensor
2) Faulty plug for sensor
3)Wire fault between plug for sensor and ECU
4) Bad ECU connection at plug in pins or ECU unit itself.

I'm going to check the MAF test now:
-Pin 2 has +12
-Pin 4 and 5 have continuity
-Pin 1 has resistance???(on 20K ohms reads 10.89)

{1) MAF check; Take the connector off the MAF. Turn the key to on(but don't start the engine). Using a volt meter check for power from the ECU at pin 2 to gnd. Should be 10 to 12 volts. Turn the key off. Using an ohm meter check pins 4 and 5 to gnd. It should be a direct connect to battery gnd. Check pin 1(signal back to the ECU) to gnd. You should see resistance of some sort(not shorted to gnd and not an open).}

"You should see resistance of some sort(not shorted to gnd and not an open). I don't know what this means other than there was resistance. I gather this means if there was a short to ground there would be continuity... the open I don't understand.

{{2) CKP check; Unplug the connector and pull it into the engine area where you can get it. Key off. On that plug the center pin to gnd should see resistance of some sort. Again not shorted or an open condition. The outer ring on the plug should be a short to battery gnd.}

On testing my CKP sensor "plug" with black probe to battery ground and red probe to center of plug (20K ohms on dial)
I have 4.60 ohms on 20K ohm reading in the center hole.
The outer ring doesn't change from 1...no mater what ohm range.

If the outer ring is a short to battery ground...there should be continuity CORRECT???
So what does this mean? The sensor wire is bad or the ECU isn't recognizing ground?

I'll test the fuel relay later.

Until the CKP is recognized ...this engine won't fire.

Once again thanks for your TIME and input.
 

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Discussion Starter #17
This is so weird. You're having the exact same problems that I'm having(had hopefully). I too got blink codes at pin 8 and nothing at pin 3. After each blink code you have 20 seconds to clear it. So hold the button for 8 seconds. Then continue on testing for more codes. Clear the code after each reading. Pin 8 and 14 will blink once when there are no codes. Once the codes are cleared start the car. It seems that no "Check Engine" light will happen unless there's a code at pin 3. So go back and check for codes at pin 8 and 14. If the codes return, there's a problem. You can check codes while the engine is running if you want but it will cause the Check Engine light to come on until you stop the engine then restart it.
If you have changed the engine harness there is really no need to do continuity checks back to the ECU connector.
1) MAF check; Take the connector off the MAF. Turn the key to on(but don't start the engine). Using a volt meter check for power from the ECU at pin 2 to gnd. Should be 10 to 12 volts. Turn the key off. Using an ohm meter check pins 4 and 5 to gnd. It should be a direct connect to battery gnd. Check pin 1(signal back to the ECU) to gnd. You should see resistance of some sort(not shorted to gnd and not an open).
2) CKP check; Unplug the connector and pull it into the engine area where you can get it. Key off. On that plug the center pin to gnd should see resistance of some sort. Again not shorted or an open condition. The outer ring on the plug should be a short to battery gnd.
3) Fuel Pump relay check; Easy bench test. The pinouts and circuit are drawn on the unit itself. Apply 12volts to the relay coil and listen for the click. Then make sure that the contacts work when you apply the 12volts!!! Leave the relay out. Look at the circuit diagram to see what 2 pins close to apply power to the pump. Go to the relay socket and short those 2 pins. This applies direct battery power to the pumps (no key necessary). Listen to the pumps. If they squeel, replace them. You will also hear the fuel pressure regulator bleeding the fuel return. It's a loud rattling noise but no worries.
As for an ECU check and rebuild, ecmoutlet.com are able to bench test any ECU so it seems. I would stipulate that you want the capacitors replaced on spec period.
You're getting a lot of views. I hope this is helping others too.
Once again thanks for the help.

The engine will not start(crank no start) due to the ECU not recognizing the CKP sensor(#24 code blink on hand held code reader) My in car diagnostic module (red LED light) lights up with key on but does not blink after pushing button. The hand held code blink reader keeps reading 24 and 30 after I clear the codes and then attempt to restart the engine. As long as the CKP sensor isn't recognized...I can't start the engine:

"
After each blink code you have 20 seconds to clear it. So hold the button for 8 seconds. Then continue on testing for more codes. Clear the code after each reading. Pin 8 and 14 will blink once when there are no codes. Once the codes are cleared start the car. It seems that no "Check Engine" light will happen unless there's a code at pin 3. So go back and check for codes at pin 8 and 14. If the codes return, there's a problem. You can check codes while the engine is running if you want but it will cause the Check Engine light to come on until you stop the engine then restart it.
If you have changed the engine harness there is really no need to do continuity checks back to the ECU connector."

"If you have changed the engine harness there is really no need to do continuity checks back to the ECU connector."

The continuity check would rule out a bad CKP plug wire on the "used" wiring harness I purchased...my reason for the continuity check For the ECU not to recognize the CKP sensor:
1) Bad Sensor
2) Faulty plug for sensor
3)Wire fault between plug for sensor and ECU
4) Bad ECU connection at plug in pins or ECU unit itself.

I'm going to check the MAF test now:
-Pin 2 has +12
-Pin 4 and 5 have continuity
-Pin 1 has resistance???(on 20K ohms reads 10.89)

{1) MAF check; Take the connector off the MAF. Turn the key to on(but don't start the engine). Using a volt meter check for power from the ECU at pin 2 to gnd. Should be 10 to 12 volts. Turn the key off. Using an ohm meter check pins 4 and 5 to gnd. It should be a direct connect to battery gnd. Check pin 1(signal back to the ECU) to gnd. You should see resistance of some sort(not shorted to gnd and not an open).}

"You should see resistance of some sort(not shorted to gnd and not an open). I don't know what this means other than there was resistance. I gather this means if there was a short to ground there would be continuity... the open I don't understand.

{{2) CKP check; Unplug the connector and pull it into the engine area where you can get it. Key off. On that plug the center pin to gnd should see resistance of some sort. Again not shorted or an open condition. The outer ring on the plug should be a short to battery gnd.}

On testing my CKP sensor "plug" with black probe to battery ground and red probe to center of plug (20K ohms on dial)
I have 4.60 ohms on 20K ohm reading in the center hole.
The outer ring doesn't change from 1...no mater what ohm range.

If the outer ring is a short to battery ground...there should be continuity CORRECT???
So what does this mean? The sensor wire is bad or the ECU isn't recognizing ground?

I'll test the fuel relay later.

Until the CKP is recognized ...this engine won't fire.

Once again thanks for your TIME and input.
 

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Discussion Starter #18
Astronomer, If I do the same test on the Cam sensor and the outer ring on the wiring harness plug is the same as the CKP...what would resolve the issue?

I did the same test and I have the same reading on the center plug with 4.60 ohms with 20K ohm on dial BUT on the outer ring I have continuity(ie a short to ground} !!!!!!!!!!!!!!!

Same principle (of grounding on outer rings) involved for both wire harness plugs????
 

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Discussion Starter #19
Astronomer, If I do the same test on the Cam sensor and the outer ring on the wiring harness plug is the same as the CKP...what would resolve the issue?

I did the same test and I have the same reading on the center plug with 4.60 ohms with 20K ohm on dial BUT on the outer ring I have continuity(ie a short to ground} !!!!!!!!!!!!!!!

Same principle (of grounding on outer rings) involved for both wire harness plugs????

Ask and answered....pin 29 on the ECU (COMPARTMENT PLUG/HFM-SFI) is for the FUEL PUMP RELAY WHICH GETS ITS' GROUND SIGNAL/INPUT FROM THE FUEL RELAY(blu/red coming from #4 on fuel pump relay)...Now I see why you told me to check fuel pump relay!!!!!!!!!! From this same HFM-SFI plug ...pin 39 is Voltage supply (circuit 87U) according to the diagram, which in turn goes to the MAF pin 2 via a Red/blu wire(but also includes electrical input from the OVP Red/blu wire. This Red/ Blu wire goes to pin 2 on the MAF(which is +12 volts according to your test with key on).

http://ww2.justanswer.com/uploads/eurotec/2011-01-08_180355_connector.pdf
http://www.autolib.diakom.ru/CAR/Mercedes-Benz/1995/E320/SYSTEM WIRING DIAGRAMS/5418.pdf
http://www.autolib.diakom.ru/CAR/Mercedes-Benz/1995/E320/SYSTEM WIRING DIAGRAMS/5419.pdf


The Cam Sensor ground comes from pin 19(NCA) on the wiring harness cable plug(connector 2 engine compartment) while the ground for the CKP plug come from pin 29 (NCA)...both of which have dashed cylinders with the sensor wires passing through them. What do these dashed cylinders represent other than this???
https://www.benzworld.org/threads/what-does-nca-in-wiring-diagram-mean.1947850/


Why does the ground work on the MAF and cam senor plug and not the CKP??? Ground comes to the MAF/cam sensor plug from the same ECU engine plug.

If that is all it is then why does one ring on the cam sensor plug have ground while the CKP ring doesn't???

All the posts /threads say the OVP isn't necessary to start an engine. I threw more money at a new OVP last night so I've broken my promise to myself not to throw parts at a problem. That's why I started with a new(used) harness. I hope I don't find that the most important sensor input wire on this harness (CKP plug) is faulty. That's my next check after the OVP gets put in.
 

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Ask and answered....pin 29 on the ECU (COMPARTMENT PLUG/HFM-SFI) is for the FUEL PUMP RELAY WHICH GETS ITS' GROUND SIGNAL/INPUT FROM THE FUEL RELAY(blu/red coming from #4 on fuel pump relay)...Now I see why you told me to check fuel pump relay!!!!!!!!!! From this same HFM-SFI plug ...pin 39 is Voltage supply (circuit 87U) according to the diagram, which in turn goes to the MAF pin 2 via a Red/blu wire(but also includes electrical input from the OVP Red/blu wire. This Red/ Blu wire goes to pin 2 on the MAF(which is +12 volts according to your test with key on).

http://ww2.justanswer.com/uploads/eurotec/2011-01-08_180355_connector.pdf
http://www.autolib.diakom.ru/CAR/Mercedes-Benz/1995/E320/SYSTEM WIRING DIAGRAMS/5418.pdf
http://www.autolib.diakom.ru/CAR/Mercedes-Benz/1995/E320/SYSTEM WIRING DIAGRAMS/5419.pdf


The Cam Sensor ground comes from pin 19(NCA) on the wiring harness cable plug(connector 2 engine compartment) while the ground for the CKP plug come from pin 29 (NCA)...both of which have dashed cylinders with the sensor wires passing through them. What do these dashed cylinders represent other than this???
https://www.benzworld.org/threads/what-does-nca-in-wiring-diagram-mean.1947850/


Why does the ground work on the MAF and cam senor plug and not the CKP??? Ground comes to the MAF/cam sensor plug from the same ECU engine plug.

If that is all it is then why does one ring on the cam sensor plug have ground while the CKP ring doesn't???

All the posts /threads say the OVP isn't necessary to start an engine. I threw more money at a new OVP last night so I've broken my promise to myself not to throw parts at a problem. That's why I started with a new(used) harness. I hope I don't find that the most important sensor input wire on this harness (CKP plug) is faulty. That's my next check after the OVP gets put in.
Bingo!!!! I think you found the problem, and your right indeed, No CKP sensor....No start(guaranteed). On my E320, the ring on that CKP sensor plug is a direct short to battery ground. Same as the Camshaft sensor plug ring.
Take connector 2 off the ECU and check the CKP sensor plug all the way back to that connector. The center pin should ohm out to pin30 and the ring should ohm out to pin 29. If that checks out ok then you probably have a corroded solder join inside the ECU. There are 2 connectors going to the ECU so make sure your test the right one. Could even be a bent pin in the connector cable assembly or on the ECU connector port so look close.
At this point all you need is ground on that CKP sensor ring and the car should start. Even if you have to run an external wire(it will not damage the ECU). Your MAF plug test results are perfect. You're gettin close.
 
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