Can the two ECM's located behind the seats be interchanged? I have symptoms of the 5,6,7,8 (drivers side) ECM is inoperable. The left bank of cylinders is shut down and the check engine light for those cylinders does not come on when turning the key. The bulb is good. I would like to interchange the two ECM's to see if the problem moves to the passangers side.
What are your exact symptoms? This sounds more like the catalyst ECU shutting down one bank, rather than a Motronic ECU issue, which is rare. Are you getting the "slow down 5-8" light coming on? The catalyst ECU's shutting down a bank is a very common problem to 348's and 355's, and you will find many threads on the problem and diagnosis.
Yes, they can be swapped from side to side. No issues. Nice plan of action for your testing. Also, each engine computer has its own fuse, and each ECU has its own relay in the passenger footwell. Meaning: swap the relays to see if the problem switches sides, too. And replace the fuses.
First things first. If you got a check engine light you will want to pull the codes. Run a search of the archives to find the instructions on how to do it. next... As has been stated, yes you can swap the Motronic ECU's from side to side. But know that when you do you will need to let the car relearn the warm up parameters. Let the car sit and idle for 10-15 minutes, I like letting it idle until the radiator fans kick on. But before you do that, unplug the catalytic converter temperature ecu's. Just follow the wire on the thermocouple, coming out of the cat, up to the cat ecu. Then find the plug on the cat ecu attached to the main wiring loom and unplug it. What happens is that when the cat ecu "thinks" it's getting an over heating signal from the thermocouple, it sends that info to the Motronic ecu's (the one's behind the seats) and then the Motronic's shut down the particular bank of cylinders to prevent damage to the catalytic converter/s. With the cat ecu unplugged the Motronic will not get an over heating signal and the car should run. But that is only part of the problem. If your car runs with the cat ecu/s unplugged, you will need to find out exactly why. Is it because your car is indeed running rich, and causing the cat to get hot? Or, is it because you have a bad cat ecu? Or, is it because you have a bad thermocouple? So first things first. 1) pull the check engine codes, to make sure it isn't something really serious. 2) disconnect the cat ecu's, to see if they are what is causing the bank to shut down Get back to us and let us know what you find.
Hi Chuck- Welcome to Fchat! I've gotten MANY compliments on the exhaust. Thanks! Let us know the results, maybe post up pictures of the procedures.
Thanks for the advice; you got me pointed in the right direction. I cleaned both plugs on the ECM in question with Radio Shack contact cleaner and the shut-down problem cleared up. All eight cylinders are firing now. I, however, was not able to locate a relay that had anything to do with the Motronic ECU's in the passingers fuse foot box. Fuses, yes, but relay, no.
