1994 e320 ASR and Check Engine light
 

Hello all:
So the cabrio throws a ASR light and goes into limp home mode, check engine light also came on as well. Managed to get the beast back home and pulled blink codes

I get no blinks from pin #3, not even a 1 blink for no-codes
Pin #8 threw 42 blinks (42 CAN communication from ASR, EA/CC/ISC module or diagnostic module (OBD II) faulty
Pin #14 I get no reading from either

Very hard to diagnose, this happened all of a sudden, and was not using cruise control, so I assume something downstream of pin#14 went bad? lost connection to DM? Are there any fuses in-line that I should check? Why no reading from pins 3 and 14?

Thanks for the help in advance

How is your brake light switch, has it been replaced? I had the same symptoms on my 99 S500, replacing the brake switch cleared the problem.

Great suggestion, I had read that the brake light switch can cause many a ASR issue just surprised at the high failure rate of these switches. It's cheap enough and available locally, that I'll swap it out and see if that is the issue.

I also recall an odd occurrence a day or so before this happening, my lamp failure bulb lit up oddly although all of my lamps worked as far as I could tell, abut 5 min later the warning indicator turned off and has not been on since. I have read of tail lamp connection issues can also throw the ASR in limp mode as well, so another DYI to look into.

Still surprised that such a problem would make the Diagnostic Module pins 3 & 14 go blank :confused:

Another update and still need help...
Some great suggestions have come my way, here's what I have done and still having the problem, so please provide additional suggestions of what else to check.

My engine wiring harness is the newer Delphi post-bio harness, so ruling that out as a problem
The ETA (EA) is also a 2005 version replaced by the PO, opened it up and it looks pristine including the wiring (pigtail) again, post-bio unit, do see this as the cause.
Replaced the brake light switch (cheap to do) no change, still have ASR light on.
Checked rear tail lamp units for grounding problems, found a brake bulb loos in its holder, extended the spring, tightened and cleaned the connections, still have the ASR light.

The only codes that I have are as follows:
DM button or (pin 3) 17 blinks
Pin 8 42 blinks
Pin 14 none, nothing, nada

Voltage to pins 3 and 8 are 11.7V and to pin 14 only 10.7V, a volt is lost somewhere but enough that I cannot retrieve any codes from this pin.

OVP fuse is good and the relay is 000 540 67 45, so should be the later good relay.

I'm down to the codes that I can pull, which indicates somewhere communication is lost (CAN communication from ASR, EA/CC/ISC module or diagnostic module (OBD II) faulty).

As mentioned the EA and harness and connector all look good.
The CC not sure what to check, although now with the ASR light on it is disabled???
ISC module, again not sure what test I can do. Currently the car starts and idles higher than normal, but because of the ASR light I assume. Had no idle problems before the ASR came on. Ideas on how to test???
Lastly the DM module itself, as stated above I have low voltage to pin 14 preventing a code reading from that pin. Any ideas of how to test this lead specifically or what might cause this???

TIA

how to disable limp home mode?

I would like to run some diagnostics, and from what I have found/researched using a jumper on the DM from pins 1 to 6 should disable the ASR, and supposedly the limp home mode.

Unfortunately did not work for me. Jumped the to pins, started the car and still in LHM. If for anything, I would like to disable the LHM so that I can drive the car to an indy to see if they can make sense of my problem.

Can anyone explain how to disable LHM for diagnostics?
One would think this is possible

Finally solved
Something failed in the e-gas module leading to low voltage output to pin 5 on the e-gas module which leads to pin 14 on the DM. This prevented initiation of codes from DM pin 14, and either as a consequence of the DM not being fully operational or something else related to that circuit in the e-gas module is what caused the ASR/CE and Limp Home mode.

Thanks to all who contributed their ideas on the board and privately and a special thanks to Arthur Dalton for his patience and excellent suggestions throughout a long diagnostic process.

Ultimately not sure still what caused the e-gas module to fail but add this to a long list of ASR fault triggers. Arthur had mentioned that they typically short when a EA goes bad, so wise decision would be to replace them both at the same time. In my case 10 years had passed between EA upgrade and e-gas module failure so I suspect something else caused my failure or the module just gave up. Upon replacing the e-gas with a known good used unit, everything returned to normal and no codes so-far.