Please help me diagnose C36 problem

[BongC36]

My 95 C36 lost power and started misfiring recently. It went into 'limp-home' mode by shutting off cylinders 1 & 6.

I sent it to the dealer for diagnosis and they replaced the MAS and the coil for Cyl 1 & 6. They said its fixed but when I drove it hard on the way home it went into limp-home mode again. Also I can feel that the power is significantly down.

I scanned the dealer's diag printout hoping some of our savvy techs can help me diagnose. The dealer wants to throw parts at it but that is way too expensive.

So far we had changed the plugs, 3 coil ends, air and fuel filters plus the aforementioned MAS and coil pack. The wiring harness had been replaced about a year ago.

Need help guys!

[BongC36]

Uh sorry, can't post the scanned printout so I'll just type it...

Res. short test Fault Memory
=======================
HFM

MB number 202 545 96 32
Diagnosis Ident 46/00

012 Idle speed contact
air mass
Implusibly large

040 Injection Valve Cyl.6
Y62y6 -//-,

094 Transmission overload
prot. switch S65

104 Fuel Safety Shutoff
recognized

035 Lambda control
rich stop/mixture too lean

084 Short-term self-adjustment
idle speed part load exceeded

117 Attempt at starting performed
with IFZ locked

110 voltage supply to HFM control
unit N3/4 implausible

==========================
TPM

182 Safety fuel shut-off switch
signal for HFM N3/4

==========================
ASR

011 Solenoid valve relay A7k1

==========================
ASD

Control unit does not answer

==========================
EGS

Control unit does not answer



That's it guys. Will appreciate any feedback

[stox]

Looks to me that you might have a electrical problem. Check your battery, OVP, and alternator.

[jnenad16]

sounds like the overvoltage protection relay(OVP), or a deteriorated wiring harness.

nenad

[benzaddict]

A lot of those DTC codes are very common and can be ignored, but the ones that stand out to me are 040(injector #6), 034(lambda too lean), 080(short-term fuel-trim exceeded). The code for a faulty injector at cyl #6 could easily explain your problem since you've been having a problem with that cylinder already. It would also explain the other 2 codes which basically mean that the HFM computer is trying to compensate for a lean running engine and is at it's maximum correction value (quite possibly due to a bad injector that doesn't spray enough fuel). Having said that, injectors don't fail in our cars very often. They do get clogged up with fuel deposits that make them less efficient, but then they usually don't set a code.

What I would recommend you do is pull up the fuel rail that holds all 6 injectors (takes about 10 minutes) and swap injector #6 with injector #5, clear all codes and drive the car to see if the problem moves to cyl #5. If it does then you know you need an injector, if not then then you know you have a problem with the harness or HFM computer. This test will also cost very little money (free if you do it) and is much better than just throwing parts at it.

Good luck....

[BongC36]

Thank you for your replies gentlemen, very much appreciated.

STOX: The car has a new battery and the alternator is about a year old. I have checked the voltage with the engine running at it varies between 13.6-13.96 VDC. How can I check the OVP?

JNENAD16: New wiring harness was installed about 2 years ago. Will check the OVP. What are typical symptoms?

BENZADDICT: Yes I am suspicious of #6 injector too and plan on doing what you reccommend when I visit the dealer this week. What is that gibberish after the injector fault entry?

If I drive the car slowly (less than 120 kph) it does not go into limp mode but I can feel that the power is down significantly. Once it goes into limp mode I have to shut it off and let it cool down before I can fire all 6 again.

Can anybody please engighten me as to error code 094: Transmission Overload Prot. switch S65?