ASR / ETA issues and troubleshooting

[Nauska]

Hello all,

Decided to join the forum to share some experiences and hopefully get some input on my current issue.

My E420 W124 1993 started having some issues about a year ago after a 6 month winter break. It was the usual, limp mode with ASR light on. Back then i diagnosed it to be a faulty ETA, but during diagnosing the issue went away and normal operation continued for the whole summer. I was pretty sure the issue would return, and sure enough, after this years winter break limp mode was back.

I checked the the ETA and the wiring harness was crispy enough to deem it the culprit. I sent it to MBK-TEC for a rebuild, got it back and assembled it. And the issue is still active. From the report it can be seen that there was no difference from pin measurements before rebuild. This would point to the issue being elsewhere, although i dont have a reference point to know whether measurements are good or not.

Additional info:

ASR code 030
Throttle valve angle stuck at 89.2 degrees (value 46 from LH1)
Limp mode / ASR light on (no electrical movement on throttle)
Engine upper harness replaced few years ago
Throttle linkage checked -> throttle flap rests freely
No communication to EFP on star (this could be due to a missing pin 7 wiring on diagnostics cable)
E-gas module checked, no visible corrosion on boards

Next steps:

Check actual values from both e-gas module contact and ETA contact to make sure if throttle position is changing on pins

Help needed:

Wiring diagram from e-gas to ETA to find correct pins

Im thinking that the e-gas module is broken, but i would really like to be certain before getting into replacing or repairing it.

Any other input is greatly appreciated, would not have gotten this far without forum anyways.

 

[gsxr]

Wiring diagram / schematic is at this link.

Throttle angle stuck definitely indicates either a problem with ETA or E-GAS module (could be wiring, but I doubt it).

For test purposes you can use an E-GAS module from any other car with LH-SFI and ASR, even if it's not the same part number. So if you have a friend with a similar car who would let you swap the E-GAS module for testing, that would be really helpful.

I'm not sure if the E-GAS module is repairable, and if so, very few shops would be able to do this. Might be easier to source a good used replacement module.

Welcome to the forum!

 

[Nauska]

Thanks gsxr, thats the plan.

I sourced a E400 that i could borrow the module from, i think i read from another post that even ASR specific module is not necessary, but not sure about that. E400 is a bit older, but i will have to check if it usable for testing once i actually see the car and part number.

 

[gsxr]

As long as it's an E-GAS module from a car with M119.97x, it will work for testing purposes. The R129 E-GAS module should work perfectly, but 140 chassis E-GAS will not have cruise control function when installed in a 124.

Cars without ASR will not have an E-GAS module, those have a T/LLR module instead, and this will not work at all.

 

[Nauska]

Some advances have been made, i measured all connections directly from e-gas connection. All potentiometers, magnetic switch and motor were quite logical, pointing to e-gas module receiving correct signals. I sourced a e-gas module for testing and luckily it was exactly the same part number. Not too surprisingly, issue was resolved, no faults and all is good. My hypothesis is that the crispy ETA cables caused a short in the cables of the motor which fried the power amp supplying the motor. I might start researching it deeper and possibly even fixing it myself, depending how easily i can source a new module (and whether i can find a schematic for the internal parts of module)

Has anybody done any research on exact codes of interchangeable modules? Mine is 124 545 4332, any leads appreciated

 

[gsxr]

Glad you got the problem solved! Thanks for updating with the solution.

There are a number of different part numbers for the E-GAS modules on the E500E and I do not know what the difference is. USA has different part numbers vs Europe which makes no sense. No other components in the system are different so they should all be interchangeable, but I've never been able to test, as I don't have any Euro-spec part numbers to try in my USA cars.

All E-GAS modules are interchangeable (at least within a given region) between 124, 129, and 140 chassis. However when a 140 E-GAS is installed in a 124/129, cruise control does not function.

I've never seen schematics for the E-GAS module, but would love to find those. I assume Mercedes never published those and they may be proprietary to VDO.