phat

I use the pulse code reader to pick up these codes from pin 8: 8 25 33 42. Where do I start to correct these codes? The car runs beautiful, no problem except the check engine light comes on

Plutoe

Clear the codes---run the car around and check for faults------do they come back or what!!

phat

I cleared them but they came right back after a couple trips

Floobydust

That many codes that come back on an HFM car tell me to check the condition of the engine wiring harness. MB used a "biodegradable" wiring insulation that degraded on the car instead of the landfill. A quick test is to examine the condition of the wiring insulation on things like the temperature sensor and the intake air sensor - if is is cracked or missing, the harness is degrading. The definitive way to tell is to look at the build date code for the harness. This will be on a paper tag around the harness where is goes behind the battery, just before it plugs into the ECU. If the build date is prior to 1998, the harness is suspect.

If the harness is ecco-junk, keeping things running will be a losing battle until it is replaced. Ask me how I know.

- FD

phat

Thank you Floobydust,
I will check the harness tomorrow. I am afraid it might be the origin of all the problems. The car runs perfect though despite the codes. Should I leave it alone? Maybe? Harness is $1000 or 10 hours of soldering.

Floobydust

Leaving alone works in the short term, but if the harness truly is bad, you will eventually damage the ECU (injector drivers, ignition coil drivers) and your repair costs will increase by a factor of 2 or 3.

I have several old harnesses. I have been soldering since I was in the first grade (really), but the two issues are: one, the harness has a molded portion that connects to the ignition coils. There is no practical way to "cut" the conductors out of the over-molded housing then repair them. Two, many of the connectors cannot be disassembled to reconnect the wiring and those that can are often old, cracked, and unusable. Believe me, I am known for being able to reassemble George Washington's wooden teeth from a left over splinter, but the MB harness is a challenge I wouldn't tackle!

If you can't afford full freight for a new harness, your best bet is a bone yard and checking the date code - many W124's had the harness replaced, but later succumbed to other deadly issues like being rear ended by a truck. They sometimes appear for sale on the forums and ebay as well.

Good luck with whatever path you follow!

- FD

phat

Thanks Floobydust,
I think I will replace the harness with a used one when I can. The molded rubber you mentioned in your post is crucial or can it be by-passed? I had great success soldering my 400e harness.
Phat

Floobydust

The ignition coils are located in between the cams on the head. There are three of them and MB uses a wasted spark type ignition system. The molded section allows the wires to neatly fit into machines channels in the cylinder head. Looks great, but probably has no real function. I'm not that familiar with the 400e harness, but if it is anything like the harness on my R129, the coils are outboard and so, so the harness does not have the feature and would therefore be much easier to repair.

Plutoe

I think you screwed up the is no fault for 25 33 and 42 pulses---read the pulse counter manual and do again-----forget about the wiring harness crap!!---Get the correct number of pulses first!!

However if you have an analog scannar with yellow in pole number 8, the faults are defined as follows

8=Idle speed control(ISC)

25=CMP sensor not recognized

33=Max retard setting on at least one cylinder has been reached

42=CAN communication from ASR,EA\CC\ISC module or diagnostic module faulty

phat

I bought the code reader on Ebay a while ago. It has the black terminal for pin 1, the red one for pin 16 and the white one for testing. When I test pin 8, I got those codes 8 25 33 and 42. I think you are referring to the codes you mentioned in your second statement. If that is the case, how can I correct the problems? Any help is appreciated

phat

I also got 2 pulses from pin 14

Floobydust

Phat -

Do yourself a huge diagnostic favor and check the date code on the engine harness. It's easy, cheap, and free.

At most, the codes you posted may point to the electronic throttle body (ETA) if your car is equipped with ASR. The harness for that is also ecco junk and also degrades. I will be rebuilding mine this winter. Otherwise, the codes don't really point to a specific fault to me.

- FD

Plutoe

First go back and clear the faults------then run the car around---do they come back!!

phat

Hi Plutoe,
Thank you for your input. I clear them numerous times. They cam back after a couple trips (short). The harness looks OK. I can't find the date tag. I did not see any broken wire covers.
Phat

phat

This car does not have ASR