Not really sure if its a country difference or something else but the 722.6 has a set of DTC's that run from 2 to 65 for diagnosis, if they run from 98 to 161 then they are intermittent faults and you subtract 96 to get the problem code if it was hard set. these all relate to P07XX codes on an OBD reader for pre 2006 cars. for example see the attached picture for the first few codes.

All of my mercedes stuff is coming up with
P2602 MERCEDES-BENZ Coolant Pump "A" Control Circuit Low
which isnt a fault code for transmissions but the aux heat system

Can you get the dealer to give you the actual DTC's they pulled from the transmission? I dont think its a country difference but it may be a specific NZ coding system.

Also whilst you can check solenoids through the plugs you have to be really careful as some are pulse width modulated (PMW) and you cant just stick some electricity into them and hope for a readable result. I had to replace one of my solenoids a bit back and it was a PMW torque converter lockup solenoid - almost impossible to diagnose as it only failed when it got hot and as soon as you applied a non PWM current across the poles they heat up and all show as defective

If you can get codes that we use in the US (all my books are mainly US) or the mercedes DTC someone here is more likely to be able to help.
Cheers
Barri

 

Greg,

Sorry for your problems. I know my way around, but a problem is a problem, and it can stump anyone...You got a good one here!

Since you have a OBDII code, I would check the logical stuff.

A) How is the chassis ground to the transmission on the bottom of the car? Nice and tight anddd clean?

B) Check your grounds in the engine bay. You will see the union of brown wires to a bolt stud. Check the nut. Even loosen it and fan the ring terminal to dislodge any dirt. Tighten the nut(s) back up....

Because you got this OBD code, the problem is a over all problem of a short.

Now, you did not say when this problem occurs. At what gear? Or does it happen on any gear?

The two regulation are oscillating all the time, or on all the time. They vary from a few Hertz to a few Kilo Hertz depending on the gear.

The 5th gear torque converter lock up solenoid is a weird one as one would think it only works when 5th gear is engaged, but it actually starts to work around 3rd gear. The shift solenoids are pulsed on momentarily on, and the valve body locks the gear in place. To release the gear the solenoid is pulsed again, so the solenoids are never on during gear engagement.

I would ohm-out the solenoids cold and hot immediately after limp mode, so you can possibly find the shorted solenoid..

Here is a great document on the 722.6 troubleshooting. It is call 772.6 Error(post 22)

http://www.benzworld.org/forums/w140-s-class/1691375-no-transmission-fluid-symptoms.html

The truth table on the shifts(post90)

http://www.benzworld.org/forums/w140-s-class/1934442-new-s600-722-6-problem-3.html

A cheap scanner is to go this route. The whole thread is meaty, but you need a Windows PC with a dedicated serial port running XP. A must on serial port, and must on XP. You cannot run a USB to Serial converter. It must be dedicated. The software is free. The scanner is about $50 USD or so...

http://www.benzworld.org/forums/w210-e-class/1574129-carsoft-7-4-multiplexer-diagnostic-tool.html

Post 84 is the non-multiplexed scanner
Around Post 98 is the software

The last 20 to 40 post is on the multiplexed scanner


Hope it helps,

Martin

 

Barri and Martin, thks for the detailed responses.

I have the dealer SDS printout, so they are actually merc codes.

Overall I have:
Under Motor Electronics P2065 which is stored in N15/3 ETC with (P0702)
Under ETC P2602 and P2600
Under ESP C1202 BAS release switch plausability
SAM-F B1003 M13 heater water recirc open or short, but component not fitted so ignore
OCP overhead control panel B1001 low voltage
plus a footwel flap stiff, figure not related

Attached the printout for easier reading.

Thx very much for the tranny DTC listings, have printed and will have a play with some ohms etc.

I am thinking there may be an intermittent wire short dropping voltage somewhere, or could be a ground as you say.
I thought the heater recirc may be a clue, but seems its not fitted? I cannot see it anywhere in my Classic DVD schematics, maybe never fitted to W203, I have it in my R129, not sure I've tried this one.

I did see a possible mechanism of metal filings shorting electrical lines in the conductor plate - this would fit the low voltage on both in and out of TCU, and perhaps also mean news is not good on the tranny :{

When it happens - not sure - had been doing it occasionally at engine start, was always resolved by engine off and on again. Actually had the feeling if I shifted too rapidly into drive just as engine was finished starting may have done it more often. Now its solid on but when they clear codes ok for a few km when they take it around the block then driving home I get a sudden issue - at least once was the ESP kicking in.

What do you think of pullling the conductor plate anyway? Not sure if they have checked ATF for visible issues yet? How many hours is this job?

Looking a bit grim, this car is in danger of being too expensive a repair to be worth it. Cost me 8k, these repairs likely to be 5k. 230km on the clock. Engine goes great, tranny was, but think it needed some more TLC, dealer should have prompted me when I bought it 80ks back and took it to them for a check over.

Thks heaps... Greg

 

Update info:
Checked the ohms on solenoids, 2 are high compared to my Star CD diag values (it says 6y1, 6y2, 2.5-4 ohms) actually read 5.5 ohms.

ETC diagnostic manual posted in post MAVA suggested says 4-8 ohms.
Anyway, if both the same and that close likely to be ok I'd think. Others are 3 @ 4,8, one at 3.3. Could even be my meter a bit out I guess. Cannot find intermittent on TCU end connector, not able to get under the car at this point to wiggle tranny end and see if anything dodgy there.

Put a bulb to draw around 3A on input power to TCU, went for a drive with bulb and multimeter monitoring input volts. Short trip no probs, no glitches, sitting quite high at about 14.5 V when driving. Batt volts around 12.1. Seems a little low, maybe its a bit high resistance, higher volts on charge, lower on discharge? But no problems at all starting, crank amps seem very good, motor kicks over well.
Of course still in limp mode. no current draw to solenoids as TCU output drive is off.

Heater REST mode - now this IS fitted and works, but cannot see it anywhere on schematics, in any place. To be honest havent seen engine fan either, is it somewhere really odd I've missed?

But my above codes read from dealer said it wasnt fitted. !?? WTF.

Will try some more analysis...

 

When they replaced your ETC did they check for oil in the plug?
the P0702 fault refers to bad connections in the plug system on the ETC. Sometimes oil is known to creep fron the transmission plug up to the ETC and contaminate the ETC. The oil itself is not the problem but the metal particles in the oil cause havoc with the system.
Even if they replaced the ETC itself can you check they cleaned out the plug and also replaced the plug at the transmission. Any work looking for electrical problems before you are 100% certain the plugs are clean and dry is a bit pointless as you cannot be sure of your readings. you can check at the transmission plug or at the ETC but if doing so at the ETC remember that it also picks up problems in the wiring harness. see attachments

When I was trying to figure out my torque converter problem I eventually replaced the solenoid but still had an intermittent problem with contamination inside the electrics plate. I had to open up the connector bus lines and clean them out. All was fine after that
http://www.benzworld.org/forums/w210-e-class/1713315-transmission-lockup-problem-2.html#post5810938

They are actually easy to fix but figuring out the problem is often a real bugger :laugh
cheers
Barri

 

Hi Barri, yes first time they gave me back the car, they emptied the pilot bushing of ATF and cleaned the TCU down, but it still balked for me when I went to drive it. (I don't have the bill yet, not sure if the connector was replaced.) So left with them and after much more trying they decided the TCU was stuffed, and got a new one. This was ok when I first drove it (immed after repair), and was fine for a 4 hr drive, but guess what 20 hrs parked later when I'm heading to catch a ferry, does it again!

In fact I had just sent the dealer the report from the 722.6 Diagnostic pdf MAVA referred me to, when I saw your post and ref to your shorting issues which support this also.

Diag manual says:
"Short circuit on the electrical conductor plate of the electro-hydraulic control unit due to deposited metal shavings
i
Applies up to transmission number 393328, thereafter the electrical conductor plate has been modified."

Feeling rather like this is causing spikes of current and tripping low voltage codes and limp...

Seems like this is a problem with too infrequent ATF change? If this is happening does it hint life of tranny is closing in?

Thanks, will talk to service guys tomorrow and see what this next bit will cost me...
Greg

 

Hi Greg
Seems like you have covered them all then - just the conductor plate, solenoids and/or harness left :grin

Just if it helps any when I had my torque converter problem - I had replaced the conductor plate about 40K earlier with a new one that had the cover over the bus lines. With this problem I had to remove the cover to see the bus lines so even with the upgraded conductor plate crap can still get under the cover and short the bus lines.

As to lasting - I did the torque converter solenoid nearly 50K miles ago, my car had its first oil change when I bought it with 134K miles on it and the oil was awful with lots of crap in the tranny oil pan. I am now at 244K miles (393000km) and working well (said with crossed fingers whilst touching a bit of wood). I change the oil every 35 to 40Km now with shell 134 though :angel
I think they are good boxes - other than the original K2 drum bearing/bush problem but they get difficult to diagnose electrical autobox problems which doom them to replacement whilst they may still be mechanically sound.
let us know what the garage says when its sorted or if they think they have found a new problem:devil
cheers
Barri

 

resurrecting this to see if anyone else has found an answer.

I have a ML 270CDi which has a new trans (needle rollers floating free in the previous trans) . I had a fault for a contact plate,so the new plate was replaced and now i have a P2602 fault. I have tried to hunt down this, including following a tip that the fuse block sandwich construction has been known to separate causing all sorts of odd faults .I have also replaced the trans ECU but i still get this low power to the solenoid fault . So...has anyone got a list of possible reasons so i can follow it and track this menace down?

 

I have a ML 270CDi which has a new trans (needle rollers floating free in the previous trans) . I had a fault for a contact plate,so the new plate was replaced and now i have a P2602 fault. I have tried to hunt down this, including following a tip that the fuse block sandwich construction has been known to separate causing all sorts of odd faults .I have also replaced the trans ECU but i still get this low power to the solenoid fault . So...has anyone got a list of possible reasons so i can follow it and track this menace down?

What are your symptoms?

I would think that you have a high-resistance lead going from the ECU to the connector at the transmission. I would ohm-out each one.

Possibly switch the two black regulation solenoids too, and look at each filter down where they plug in for sludge accumulation.

Martin

 

Hi,thanks for the reply. I have done that. When the new trans was fitted it immediately showed a fault, the trans indicating no power to the pressure solenoid. I replaced that, but when doing so I checked the contact plate and found no connection to the solenoid in the plate itself so i fitted another plate.The first fault was gone only to replaced by this P2602 no power to the solenoids. I will recheck the loom which I suspect may have a bad connection too, Having been through the wiring several times i am getting a little tired of this car. The solenoid checked out OK.
Symptoms? the car is in limp home mode, low throttle response, drive and reverse only, no low gear selection with the tiptronic. When scanning i am not getting any readings for the trans dataflow although both ECU's i have have checked out perfectly, no oil etc.

 

Not sure what country you reside in as you have not filled out your profile.

What year Vehicle? V6? M112 engine? How many Miles or Kilometers?

You have checked your fluid level with one of these:

722.6 dipstick | eBay

You have checked your fluid level while the vehicle is idling? (I'm covering the possibilities)

I rebuild these transmissions the 722.6 is really a tough transmission(in its entirety), yet the shifter can be taken out of commission if fluids are spilled on it, but the rest will tolerate a lot of abuse.

My approach would be to "ohm-out" the conductor plate from the TCU connector. The attachment has 722.6 test procedure, and a link to a service manual. If you suspect a open, high resistance point. Then I test at the pins on the conductor plate, and test continuity from the TCU pin to the pin at the circular connector. One thing to note is the pins on the harness are generally soldered in, but I would reflow both, yet you may have pin on a few strands of wire, yet it can "ohm-out" well, but under load it can act as a resister in series.

The TCU connectors have a cable tire at where the bundle of wires come out. Cut the cable tie at the end. Then on one of the ends of the connector one has to press a tab(or pull the tab a bit), and connector cover slides away from the bundle of wires(I cannot remember as I do not take the cover off too many times)

http://www.benzworld.org/forums/w140-s-class/2544649-new-revised-722-6-service-manual.html

Does it go into limp mode right away (cold car or hot car)?


You have reset your adaptations?

Is your second TCU new or used? Have you opened the second TCU, and looked the solder joints at the pins on the connector blocks? The solder joints look uniform and flowing-Not cracked around the center of the pin...?

Ahh, for the fun of it(not that it is related). Put the car in drive(engine off). Measure the resistance of the temperature sensor, and it should near dead-on to the chart...in the attachment...

Martin

 

I would start from the top and work my way to the bottom.

I would check the voltage between pin 30 (ground) of the TCU connector 1 and pin 38 (solenoid supply) of connector 2. It should read about 11 to 14 volts.

If good, then I would disconnect the transmission plug and read the voltage between pins 12 and 6.

Also you can read the resistance between pin 6 and pin 38 at the TCU plug end.

 

Hi, thanks for the reply, I have done this but i am beginning to think there is a dry joint somewhere .I did check voltage and i wasn't getting anywhere near battery voltage out of the ECU where it is supposed to be . probablty spend a few hours resoldering the spare ECU and see if that does anything... Cheers!

 

Hi Mava,I'm in Australia ,and it's a 270CDi ML, 260,000 ks on the vehicle but zero on the trans .(this is the only thread i could find in english ) There's no gear shift,just the limp home mode. Doing the usual things like disconnecting the battery, stopping and restarting don't work, neither can i reset the fault code with the scanner .I have access to the WIS but even after spending a week reading through procedures etc nothing indicates how to sort this P2602 out. I am probably going to buy a new pilot bush and contact plate again (3rd time lucky etc ) plus i might just buy a new loom if i can figure the part number of the many in the EPC.
After 13 years on here you would think i would have filled my profile...probably did but it's faded over time..ha ha

 

Hi I've been right though the test proceedure as laid out in the WIS and the grey wire to plug terminal #1 is dead,no voltage. anyone got any idea where this gets it's power from ? Both fuses are OK ,and the relay on circuit 15 appears OK.

 

You need to update your user profile including production date. There are four different wiring diagrams for W163 ETC.

Pin #1 is diagnostic output. It goes to pin #11 of data link connector.

Go through entire test sequence and post results.

 

Is a bad solenoid out of the question? Assuming the solenoid in the circuit throwing the code is on the contact plate, would you get a different fault code if you swapped positions of the solenoid pairs?

Sixto
83 300SD
98 E320 wagon

 

W163 270CDi 2002 MY .

Ok, I rechecked everything, the data link connector is showing power. I have run the ohm meter over the cables from the ECU to the trans and found yet another dead link... I am not happy, this is the second damn contact plate I have fitted. I am going to see if it is just the pilot bush with maybe a damaged pin before dropping the damn pan again. I am heading out for a job this morning but will update when I get back to the shop and look further into this debacle. BTW using my cars VIn i get the correct wiring diagram for my vehicle in the WIS.

 

Ok, I rechecked everything, the data link connector is showing power. I have run the ohm meter over the cables from the ECU to the trans and found yet another dead link... I am not happy, this is the second damn contact plate I have fitted. I am going to see if it is just the pilot bush with maybe a damaged pin before dropping the damn pan again. I am heading out for a job this morning but will update when I get back to the shop and look further into this debacle. BTW using my cars VIn i get the correct wiring diagram for my vehicle in the WIS.

What dead link?

Attached is worksheet to check basics. If you are serious about finding the problem you need to be systematic.

 

Ok an update, i have checked the voltages at all of the pins on the ECM .#38 ,according to the wiring diagram feeds the current to the solenoids, and in turn ,the current flows back to the ECM through the solenoids and are thus switched on or off. The wiring diagram shows V+ @38 .How many volts should there be? I have 3.76 V at present.

 

Further to the above, because the WIS is updated constantly a lot of useful info is deleted such as Sheet GF27.80-p-3012G. It says" operation
In order to ensure a safe driving state and to prevent damage to the automatic transmission,the ETC control module (N15/3) switches to limp home mode in the event of critical faults.A fault code assigned to the fault is stored in memory.all solenoid and regulating valves are thus de energized ".

So... that explains the 2602 fault ,ie no power to the solenoids(3.7 volts in my case.). Now... to find the fault .

 

So if you clear the TCU and ECU faults to remove the limp mode condition, turn the key to IGNITION ON, and then measure the voltage between pins 30 (C1) and 38 (C2), you should read 11 to 14 V. right ?

 

This is one of those faults that comes back instantly after key off/on cycle.

 

Ok, After an hour or so of testing cables ,looking for cracks in the ECM's PCB (nothing out of order there) , I did find the link to the y5 solenoid is dead. That didn't show up on the scan, just the p2602 code. So after doing all the usual continuity tests on the trans feed cable ( I pulled it up into the car to make it easier to check ) all of the cables including #16 ,which was the dead one, tested OK with around .01 ohms.

That only left me with one option, test the contact plate in place with a little test tool I have,basically a cable plug with the leads still in it. I just plugged that into the trans and ran the meter over the lead ends. All except #8 lead were OK . That of course meant dropping the pan and having a look at the contact plate and the seemingly dead solenoid .
Once I had the shift plate assembly out and on the bench I saw immediately what was wrong .... it has a pin missing . Where are these damn things being made? (or need i ask?) .
So tomorrow I am going to retest all the solenoids ,then fitting contact plate number 4 and I will see if pin 38 on the trans ECM is delivering battery voltage . I notice there is a voltage regulator chip in the ECM and if I still can't get battery voltage I will try and get a replacement chip. onwards and up wards....

 

Once I had the shift plate assembly out and on the bench I saw immediately what was wrong .... it has a pin missing

Missing pin, where? Pictures?

 

There are 12 wires, (even though the connector is usually refereed to as "13-pin"). No pin in pin#5 position on the conductor plate connector, and no corresponding socket on the vehicle harness connector.

An open on y5 grounding pin (pin 8 on the conductor plate, when you check continuity between pin 6 and pin 8 as you look into the conductor plate connector) should not cause the P2602. There is a specific code for that (internal code 99).

Also checking the cable harness involves in not only checking the continuity between the two ends, but also checking for discontinuities between the suspected wire and the other wires. This would make sure there is no shorting between the solenoid supply wire and other wires (just check from one end while the other end is disconnected).

I think the TCM power supply has a built in protection against shorts. Few days ago some other poster had the same P2602 with 3.7V at pin 38, and he ended up removing the conductor plate, removing and checking the solenoids, and installing a new plug adapter, and clearing the faults at the TCM and the ECM. His problem was solved.

 

Having carried out this exercise more times than i want to count I am getting to the stage where i might just try a new pilot bush and order a genuine plate from MB . Everything is new already which really has me scratcvhing my head .
Today i opened up one the ECMs i have plugged it in and checked the voltages . As before, i am still only betting 3.9 volts at #38 . So it's some sort of shut down mode. I checked the AAM for faults and there's' nothing there .
I have read off the voltages at the voltage regulator chip, 11.97, then 10volts,then 5 followed by a 0 then 3.9 .3.9 and zero. i have no idea if these are correct and the WIS suggests that the fault is cables or the ECM ... i need more info on this ECM before i commit to spending more cash.

 

Glad you found the problem. It comes down to insertion of that connector plug. Yes, the pins are fragile, but jamming-in the plug is not the solution.

Practice the proper insertion and removal a few times. Lube lightly the seals. Here is the process..

http://www.benzworld.org/forums/w210-e-class/1570724-my-attempt-replacing-transmission-plug.html

All the best,

Martin

 

One of the pins #8 in the contact plate wasn't there .So today I fitted another new plate ,i double checked everything after fitting it to the shift body and again when the shift was bolted back in.. Cables all measured within specs to indicate all the solenoids are working /connected as they should be... annnd .
I hooked everything up,filled the fluid and double checked the level at cold . Fitted the scanner, turned on the ignition ,let the scanner do it's thing and read off the code!!! yes i have a new code .

P2107 The internal electrical check of Component Y3/6y1(Modulating pressure control solenoid valve) has failed.




The ECM is still showing only 3.76 volts and the fault code will not clear . Do I have a ECM fault? this NOT a throttle switch fault or faulty solenoid as they all tested well within spec. (GM cars use the same number to indicate a fault with fly by wire throttles) .


A note on these plates. i have a couple of old original plates here with mercedes markings. The new ones came in boxes marked Febi but there are no part numbers or other ID . The two halves are held together with little white plastic pins. The originals are riveted and glued by the look of them.

 

I have to ask again since I reread the thread but didn't see a clear answer - how is the solenoid in question acquitted of fault? After all this time I'd have thrown in a set of known good solenoids for the heck of it.

Sixto
83 300SD
97 E320 wagon

 

When are you measuring the voltage on pins 38 and 30? With the ignition ON or with the engine running ? You should measure it with ignition ON the key position (RUN), when the engine is not running. The MPC (modulated pressure control) solenoid works with pulse width modulation (pulsing the pin 36 at the TCM). This will adjust the exhaust from the solenoid based on differing line pressures (just like a fuel injector operation). So just a resistance check will not 100 percent check the operation of the MPC. There may be something wrong with the MPC (stuck) or not properly installed (no o-rings so the mating surfaces must be absolutely clean).

A solenoid check should also involve in the actual valve operation action, which can be done with a coupling hose, and pressured metered air. This will ensure that the solenoid is not stuck and electrically operational.

 

"One more thing; all six solenoids
are pulse-width-modulated and have a
low resistance so don’t get cute and fire
up the shift solenoids for any length of
time with straight battery voltage. If you
want to shift this transmission electrically
use a 5-volt power supply."


Respectfully, I do not agree with this statement. Only MOD PC, SHIFT PC and TCC work with PWM (strictly meaning, to regulate the flow). The other 3 are ON and OFF.

Second, Witek did not say you connect a car battery directly. The supply voltage to the solenoids is 11 to 14V (see Startek) and the solenoids are PWM'med or turned on/ off via application of ground. I am sure within the TCM the power to the solenoid is "derived" and regulated. so there is current limiting there, plus a rudimentary current sensing circuit, so the solenoid operation is checked. The important factor is the current really, not the voltage to certain extent. The electrical continuity and the resistance of the solenoids can be done with a good ohm-meter, but this does not guarantee an actual operation of the solenoid controlled valve.

Note also that while the car is in Park / Neutral the MOD PC and SHIFT PC are pulsed with 40 and 33 percent duty cycles. So if the voltage measurement are done across these while IDLING, you will have much less voltage across them due to averaging nature of the multimeter. It is best to use a scope for these voltage measurements if available.

 

Only MOD PC, SHIFT PC and TCC work with PWM (strictly meaning, to regulate the flow). The other 3 are ON and OFF.

What you say seems reasonable. I was quoting the Automatic Transmission Rebuilders Association article, and assumed they know whereof they speak, but mistakes are made; maybe they got it wrong.

Second, Witek did not say you connect a car battery directly.

Pretty much, yes, that's what he said:

Get assembled valve body back on the bench. Using your test connector apply 12V to voltage supply. Then in turn complete the circuit for each solenoid using amp meter connected in series. Note current consumption for each solenoid.

If it's on the bench with a test connector, we aren't feeding current to the valve body's solenoids via the EGS, so any theoretical current limiting that may or may not exist is moot.

"Don't use a non-current-limited 12v source to test the solenoids" is my interpretation of ATRA's advice, and I think that's good advice. Just because the shift solenoids are not PWM does not imply that they will handle being fed 12v for more than seconds. As an example, it's quite common for diesel glow plugs to be rated for 4, 6, or 8v and be installed in 12v circuits. Exceed the duty cycle and they're shot. Could be a similar situation for the 722.6's shift solenoids. We don't know: use 5v supply for testing.

I agree with all else you said, esp. use of a scope if you want to watch the duty cycle, but I suspect the OP's problems is not going to require data that fine.

From what I understand, if P2602 is being set (disabling all EGS outputs, rendering the AT to hydraulic-only operation: limp mode), waveforms won't matter: the circuit is open or shorted.