I suspect my ECM may be bad, but was looing for a little advice before I shell out $260 for a new one. My 1990 240 (B230F) Wasn't running for almost a year, and I recently got it back in shape. It's been running fine for a couple of weeks (probably 300 miles or so), until the other day while in a drive-thru it died. It started right back up again, but a couple days later on the freeway it suddenly lost power, then ran normal. This happened a few times until I hit a stoplight coming off the freeway and it died again, and would not start. Half an hour later it started again, then died after driving a couple hundred feet. After having it towed to my house, it has started up and run fine every time I try it, although I'm afraid to take it back out on the road until I figure out what's going on.

It was showing no trouble codes, except once I let it warm up it read 3-2-2 (MAF sensor burn off signal absent or faulty). I cleaned the MAF and ran it again after clearing the code, and now get no codes.Since it seemed to run fine when cold, I thought maybe the O2 sensor was bad, so I checked it with a multi-meter the way my Chilton manual said to, and it told me the ECM needs to be replaced. With ignition turned to run and engine off, no voltage to O2S lead. Checked circuit for continuity and resistance, but only read 2.5 ohms instead of the 5 ohms the manual said I should have.

My question is, shouldn't I have a 1-1-2 (control module) or 2-1-2 (HO2S signal) fault code if the ECM is bad? Could it be bad and still show no trouble code? Any other suggestions on what to check? Thanks in advance!

check fuse in sealed fuseholder in 5 sq mm wire near Left front suspension tower top. It goes straight to the battery +ve. This primary fuse & holder often corrodes at this age-clean carefully, and replace if it won't clean up. Use copper or brass fuses everywhere-not aluminium, as they corrode and insulate out. The fuseholders' cap is removed by depressing the safety lock and pulling up. I think it pivots about one end. NB MUST be dry when resealed! iff ECU failure-it prob would be terminal immediately, and not restart.

A random stall like this is almost always the crank position sensor (or less likely the fuel pump relay).

The best test for the O2 sensor is to measure the voltage on the fat green wire while the car is running.