Mercedes W202, C200 cyl 2&3 misfire and possible PMS fault

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agbekas

New Member
Joined
Jan 9, 2023
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6
Location
Greece
Car
Mercedes W202, C200 (136Hp), 1995
Greetings to all members of this excellent forum.

I live in Greece and I own a Mercedes W202, C200 (136Hp) model 1995 with manual transmission (VIN: WDB2020201F-297048).
The car has been parked for quite some time (over 4 years) in an underground garage. However, at regular intervals (once or twice a month) I turned it on to run the engine and circulate its fluids

My problem with Mercedes started when I started smelling gasoline from the engine compartment. I found that the leak was from the pressure damper which I replaced. While trying to replace and not knowing the problem with the Mercedes biodegradable wiring harness it seems that by touching some wires the wiring system started to collapse.

I ordered new wiring (rebuilt with new materials from Germany) for both the engine and the ignition coils. A friend of mine who is mechanic took out the old one and installed the new one.

And while I expected the problem to be resolved unfortunately the car seems to be working on two cylinders 1+4, cylinders 2+3 are not working.

From what I have read on the forum, a possible reason for the 2 cylinders not working is the faulty PMS Unit due to shorts in the wiring harness. The code for this unit on my car is A0185451132. Firstly, I would like to ask the followings:

1) Besides the PMS unit what else could be causing the 2 cylinders to not work?

2) The new PMS control unit must be programmed before it is installed in the car? From what I have read on the forum (posts form grober and neilrr), PMS units for old Mercedes are not programmable and are just plug & play. On the other hand, my car has the one button flip ignition key (see picture) which controls the doors unlocking/locking and the theft alarm and the interior mirror (see picture) is the one with the red/green flashing lights when the alarm is set to on/off. Therefore, I fear that it might be a connection between the two units (PMS unit and ignition key) in order to start the car.
Any help would be greatly appreciated since the car is parked in a garage and cannot be taken to MB service
 

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Thanks for your reply neilrr.

I have read in forum posts that several owners of Mercedes W202 (or W124) dated 1994-1996 who had a problematic PMS unit due to disintegrated engine wiring harness or faulty ignition coils, solved their problem with PMS units that you supplied to them.
It would be great if any of them can confirm that their Mercedes'es had also the one button ignition key and the inside mirror with the red/green lights and that the transition was simply plug & play (and hopefully not pray)
 
I just told you it is plug & play. All PMS units are plug & play.
 
Your car has a lost spark ignition system. Plugs one and four are fired together by one coil and two and three by another. The fact that 1+ 4 are firing means the PMS unit is getting power. Locate the coils and try swapping them if one and four stop firing and two and three do fire then you have a faulty coil or coil supply. if not then theres a PMS problem
 
Thanks grober. I'll do the swap and I'll get back
 
Grober
There is no need for the ignition coil swapping test, since all four cylinders are getting spark. What cylinders 2&3 don't get is fuel because of lack of pulse/current in the fuel injectors which feed them. As an additional note, the whole fuel injector rail has been disassembled and the injectors are fine. They are not getting any signal to start spraying fuel. Any thoughts under these new evidences ?
 

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