Help needed with getting/reading ECU codes on 348

Here are jpg and htm files that have the information you want.

Bruce

 

In case this isn't perfectly clear from the above post, you have to make sure the "pigtail" for the pushbutton is plugged in at the Motronic unit. The passenger side ECU controls the 1/4 bank only, and activates the "check engine" light for the 1/4 bank only. Test one bank at a time (someone here once told me that he could do both banks at once, but he must have far greater brain capacity than I could manage!). Follow the procedure as shown, make a record of the fault codes indicated by the flashing lights, then reset the ECU (clear the memory).

I'm not an expert at this, but I have performed this procedure several times in the past. Apparently, the Motronic ECU will register and store a fault with the catalyst and/or its ECU (code 4121 or 4122), but the "real time" warning shows up as a "slow down" light, not as a "check engine" light. It's still quite likely that your problem is one of the catalyst ECU's gone bad. Very, very common.

 

OK - I'm trying my first bona-fide technical advice here.... please don't laugh (or sue me) if I'm wrong.

Look straight down, connected to the exhaust. You'll see coffee-can sized cat's -- one on each side. There should be a little wire going into the top-side of each cat. Pull it out those wires and store them neatly (away from anything too hot -- voila, you're done.

Wire 16 is the thermocouple. I believe that's the culprit.


(Ernie/Jeff, how'd I do?)

-Daniel
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Are you sure Bill Gates didn't design the car?? I'm totally lost now...
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If your cat DOES malfunction, methinks you'd wanna know. Before you smelled your rear bumper burning.

 

I would not take the connection out of the Cat, but disconnect the wire from the ECU output side. If you take the connection out of the Cat you will have an exhaust leak. If you disconnect the wire from the Cat to the ECU, a bad ECU will give a false reading. I replaced my Cats with test pipes with the fittings connected for temp and O2 and just ignore the slow down lights. If you keep the ECUs connected and a bank of the engine cuts out, switching off the key and restarting has cleared the problem for me.

 

Close Daniel but the wrong end of the wire. If you look at the diagram that Daniel posted you will see the number 38. That is the bolt that holds the exhaust ecu to the subframe. You can see two wire connectors, those are the ones you wanna unplug. The first one, number 16, gets the signal from the cat, then the second one, number 43, sends it to the Motronic ecu. You really only need to unplug number 43, it doesn't hurt to unplug 16 either. However leave the end alone that is attached to the catalytic converter. That is the end that Daniel so kindly circled in red. Just messing with you Dan. Anyway this is just a temporary way to see if it is a bad exhaust ecu, not a permanent fix. If you open up up the engine deck lid you can see the exhaust ecu mounted to the bottom part of the shock tower, just underneath the coils. You can also follow the wire coming off of the cat going to the connector, attached to the exhaust ecu. Unplug it and see if your problem goes away. It may, and it may not. If it does go away then you have a bad exhaust ecu, or the cat is bad. If it doesn't then it is something else.