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1994 E420
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Discussion Starter #1
Acquired this Car in 2004 from NC. Its in Canada now with 205000 miles.
ASR light on at all times. Car is in limp home mode.
Had my mechanic scan using his Snap-on shop scanner.
Following codes came up. They were cleared and resurfaced after a test drive.
Codes 30 Central Lock
Code 4 Voltage at hot wire MAF sensor (B2/2) insufficient or too high, or open circuit in ground wire at hot wire MAF sensor.
Code 22o2 Heater G3/2 open / short circuit.
Code P0133 O2 Circuit low Resp.
Code 0131 O2 Circuit low Resp.
Both upper and lower harness replaced
Date on ETR is 03M03
Can the MAF Sensor be the reason for the ASR light and resulting limp mode?
 

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Buncha W124's
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"Code 4" for the MAF is from the LH module, but no, a fault with the MAF can not cause limp mode... it would cause engine operational problems or emissions faults. "Code 22", O2 Heater G3/2 open / short circuit." is also from the LH module, but also would not cause limp mode.

The other codes and code descriptions are not valid / incorrect. There is no code for "central lock" on the 124 chassis, at least for North American models... where is "NC" and what country was it originally delivered to?

The codes for "O2 Circuit low Resp." are also invalid; there is no such code description, and Pxxxx codes are for OBD-2 cars, not the W124. It sounds like your mechanic's scanner is not fully compatible with the W124. You would get better information yourself using a hand-held blink code reader to check codes on all 5 of the powertrain computer modules (6, if the car has a Check Engine light). Click here to download a PDF file with the factory codes for your car, and an explanation of what computer modules are present.

You will need to pull codes from the E-GAS module specifically, to determine the cause of the limp mode. Common causes are a faulty starter lock-out/backup lamp switch (S16/1) on the transmission, faulty ETA (M16/1), mis-adjusted throttle linkage, faulty brake light switch (S9/1), faulty accelerator pedal switch (S29/3), or even a bad E-GAS module (N4/1). But without the E-GAS codes you would just be throwing parts at the problem. Search the forum at 500Eboard.com, there is a ton of information there on diagnosing limp mode on the W124.034/.036 models, and also info on how to read codes.
 

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1994 E420
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Discussion Starter #3
Hi gsxr. Thanks for your prompt response and sorry for late reply. Been trying to acquire a code reads.
Agreed that mechanic codes were not as I expect. Will definitely let him know of my findings with the code reader.
Car was purchased in Winston-Salem, North Carolina, USA in 2014 and not 2004 previously mentioned.
2018/2019 was first winter driven. Very clean with no rust. My 38 pin hook up has only the following pins with contacts.
PINS 9, 20, 22, 23, 25, 26,31,32, 33, 36, 37, and 38.
Pin 9 - 3b blinks and 8 blinks
Pin 22 - 8 blinks
No other pin shows any blink. However, pin 37 result in a click on the left bank of the engine.
After the codes were recorded and cleared, car will crank but not run. Let it sit for half hour and crank again. With some coaxing it ran as if 3 cylinders alone firing.
Don't know what this new problem is. Prior to the codes, it ran real healthy but with limp mode, and no missing cylinder.
Unable to make sense of my findings with the link you sent.
Your expertise needed here, Sir.
 

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W124
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I'm sure Dave (GSXR) will pipe up with his thoughts. Otherwise, he DID point you to the 500 forum. That forum is dedicated to the M119 powered 500e and therefore has much more information on problems 400e, e420, e500 and 500e experience. Having said that, you probably have a new problem in the distributors that is causing the inability to start and poor firing. Remove both caps and wipe down/dry the cap, rotor, dust shield, etc. This might help you get it running again but the correct solution if this gets it running is to replace the caps, rotors and dust shields.
 

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Thanks for the additional info. I wanted to confirm if it's a North American-spec car, which will have the Check Engine light, and Diagnostic Module (powertrain computer #6).

The "new" problem where I would not start, then a half-hour later fired but ran on probably 4 cylinders, is likely an ignition issue. If you let it sit longer and it eventually fires & runs normally, the root cause may be fluid on the back side of the insulators behind the rotor bracket. Search the 500Eboard forum, there have been many, many discussions covering this in detail. If the caps/rotors are old or badly carbon tracked, it would probably be a good idea to replace everything (caps, rotors, insulators) at the same time. If you end up doing this, get Beru caps/rotors (may only be able to find the rotors on eBay). Bosch is the only mfr for the insulators.

I think your 38-pin hookup is not properly compatible with these cars. Can you post a photo of what it looks like? There should not be anything on pins 9 or 22; see page 3 of that PDF file. You may need to get a different setup to properly pull blink codes. Page 2 of the PDF shows the only pin numbers you SHOULD be able to get codes from (4, 6, 7, 8, 16, 17, 19, 30) and two of those are not powertrain related and can be ignored (pin 16 = ACC, pin 30 = SRS).
 

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I think you are numbering the pins incorrectly. #1 is bottom right in that photo. What you may have thought was #9 was actually #30, and so on.

What you thought was #22 was actually #17 (EZL / DI), and blink code #8 for that is not critical, it only affects full-throttle shifts.

Check codes on pin #7, second row up from the bottom in your photo. That's for the E-GAS module.

2613458

 

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1994 E420
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Discussion Starter #8
Thanks Guys. Just check blink codes again with the corrected pins.
Only pin with blink code is 17. It has 12 blinks.
I opened the right side (passenger side) and checked rotor and cover. Minute contamination only. Only a little trace of fluid at bottom at drain.
Rotor and cap looks real good. Changed 12,000 miles ago. Also changed ignition cables.
Motor runs real rough and shuts off in a few seconds after a noise at front right engine.
I need to get it back t running smooth even in limp mode so that we can then look at other possibilities.
 

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Noise from the front right of engine, at cold start, is probably the air pump (smog/emissions pump). You can unplug it for testing purposes, but if you leave it unplugged it will trigger the CEL (and a code on both the LH + DM modules). The pump has zero effect on how well the engine runs, it's a separate issue.

Did you remove the rotor, AND rotor bracket, to check the back side of the insulators? Pics:



 

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1994 E420
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Discussion Starter #11
I opened and inspected distributor cap, rotor and remove and inspect insulator. There was a small trace of oil at the bottom of cap.
Motor cranks, starts level for 2 seconds then stumbles and die. At cranking I hear something like the starter motor disengaging a few seconds after engine starts and cranking stops. Sounds as if there is a delay before the starter motor disengages from the fly wheel. When I add gas the motor increases rpm, stumbles roughly and I hear sound as if it sucks air or blows air like a misfire. Motor dies as soon as I let go of the gas. See attached pictures. Need help to get it running level again then focus on the ASR and limp mode. This rough idling started inly after I use the blink code reader. There was a sound when I read code from pin 2. Sounds like gas gushing with a clicking sound somewhere under filter housing on the left side of the throttle body. I even smelled the gas. Is this normal? That was the only strange occurrence when I read the codes. Backside of Insulator.jpg Behind Insulator.jpg Rotor cap.jpg
 

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I opened and inspected distributor cap, rotor and remove and inspect insulator. There was a small trace of oil at the bottom of cap.
Looks like the seals on the cam sprocket (which drives the distributor) are leaking. There should not be that much oil behind the insulator. It could possibly be related to your misfire. At a minimum you should clean everything up, including the back of the insulators. The caps look clean inside.


Motor cranks, starts level for 2 seconds then stumbles and die. At cranking I hear something like the starter motor disengaging a few seconds after engine starts and cranking stops. Sounds as if there is a delay before the starter motor disengages from the fly wheel. When I add gas the motor increases rpm, stumbles roughly and I hear sound as if it sucks air or blows air like a misfire. Motor dies as soon as I let go of the gas. See attached pictures. Need help to get it running level again then focus on the ASR and limp mode.
I'm not sure why you hear something at the starter after cranking stops, that is odd. If you squirt starting fluid down the MAF (only 2-3 seconds of squirting), does the engine fire and run normally for a couple seconds? If so, you have a fuel delivery issue. If there's no change, it's not fuel.


This rough idling started inly after I use the blink code reader. There was a sound when I read code from pin 2.
Pin 2 is +12 volts! There is no diagnostic line to any module on pin 2! Please use the directions on my site (link)...


Sounds like gas gushing with a clicking sound somewhere under filter housing on the left side of the throttle body. I even smelled the gas. Is this normal? That was the only strange occurrence when I read the codes.
You should never smell gas, ever. Find where that is coming from. The sound of gushing may be the fuel pumps turning on and pushing fuel through the rail. But that should never happen when reading codes. Normally the fuel pumps run for 1-2 seconds when you turn on the ignition, then turn off until the engine is cranking or running.

Do you have a spare LH module (from any other M119, 4.2L or 5.0L) to swap out as a test?

Photo attached of what it should look like behind the insulator - zero trace of oil.
 

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