'97 C230 ECM fault

Ok... the car came in the shop missing hard... had a code for mass air flow (which we easily solved by putting the breather tube back on) and a #1 misfire code... We scoped it, n replace the bosch +4 plugs that the owner had installed himself just for grins n giggles. Next we gave a listen to the injectors, and bingo... the # 1 injector was dead... we then checked the connector with a noid light and it flashed... SO, rether than just put a nes injector in it, I pulled the fuel rail and swapped injectors 1 n 2. Hooked everything back up and the trouble code followed the injector... (misfire code on # 2) Here is where it gets weird.
IWe had to order the injector and when it came in that evening i installed it in place of #2 (which was the bad injector that came out of #1) Fired it up, and it STILL HAD A MISS !!!
I rescanned it and got another #1 misfire code... go figure. but in addition to the misfire code, i got an injector #1 circuit malfunction code. (i'm really curious as to why i would get that since i had a blinking noid lite in the beginning. Nevetheless, and correct me if I'm wrong, but the ECM actually grounds the injectors thus creating the injector pulse. SO, we found a salvage unit (since a new one is $2100 and sent my customer into shock) Well, with that one installed, the car wouldn't even crank. Put the old one in and it starts right up... Tell me I'm right in suspecting the ecm at fault here... there is batt voltage to one side and continuity from the connector to the ECM....

[stevebfl]

I would check for a plug wire problem.

The fuel injector will be turned off if a misfire is detected. This is often the reason for one injector to be shut down.

I wouldn't be surprised that the controller can't be moved once its learned the car. All units after 98 would be I'm not sure on how DAS interacts on a 97.

[joe p]

Ok, this one is going to leave you scratchin your head but, the coil harness might be bad. I've replaced a few for wandering misfires before, also be sure to clear the code or at least let the cluster go to sleep before recranking once you have a skip. (dunno why the cluster will go to sleep and ME2 decides to relight the injector. )

ME2 cars are coded and married to the vehicle, yes they can be cleared and recoded but, I beleive Benz is the only one with the software to do this, they should be order coded by VIN. Wrong ME2, no start auth.

These also have issues with engine harness's but, most cause egr, knock sensor and mass air flow issues. However, dont write off the potential for a bad a/f meter. Just be sure to check that coil harness. Engine harness's are kinda tough as you have to remove the intake but, generally only take about 4 hours to get on.

Places to look for bad engine harness's on these, knock sensors, a/f meter leads, egr switchover valves, cam posistion senor leads and injector leads.

If you run into this on a SLK with no skip but full of misfire codes, there is a EA update along with the harness connector for it. (nope, aint got a clue what a EA has to do with misfire)


Joe