Bad ECM or Chip???

[Manny]

This is kind of long so if you want to bail, it's ok...

 

I have a 92 Euro 3.4L. If I use a jumper between terminals A & B on the ALDL, the codes (when there are any) come out just fine. If I use a scantool, I get an error. (yes the scantool works, I’ve used it on several other cars, including some W-bodies, with success.) The book that comes with the scantool suggests measuring the voltage between terminals A& B. If the 5 vol signal reference from the ECM is present, and you still get a tool error, you may have a bad ECM. But the car runs fine, everything works (except for the A/C)

 

Here’s what makes me think the book may be right:

 

I evacuated my A/C just the other day (29 hg for 6 ½ hours, wanted to be sure there was no moisture left ). As I was adding the 134a, the clutch wouldn’t engage (yes, the clutch works, I removed the A/C relay and ran a jumper wire between terminals 30 and 87 and the clutch engages). I removed the lead from the A/C pressure sensor, and put a paper clip between the signal reference pin and the switch input (makes both fans run), but it should also engage the clutch and it doesn’t. It appears that when I press the A/C button, the ECM is not telling the clutch to engage, even after I jump the pressure sensor lead.

 

I’m at my wits end…Bad ECM or Chip?

[Guest Gp crazy]

there are two plugs on the ac compressor i believe one is red and the other is black make sure that there all pluged in. pinched or grounded out wires to the block in the wire harrnes. you may want to check the wires from the second plug you tested trace them back. i think that is where your problem lies. i don't think it's the chip or the ecm . i think it's an open wire in the system!

just a thought jeff b\ 8)