I jumper the A?B terminals on the 88 305 TPI Trans AM and rather than the system going into diagnosis mode and flashing any codes the primary cooling air fan goes on. Help.

I tried to check the ECM for power, I think it is the Black plastic AC box 4"x 5" under the passenger side dash panel, with about 10 wire connections. I find 4- 5 V power on some of the leads.

Any idea how to get a wiring diagram the one in the Chilton's book doesn't cover it.

 

The 4x5" AC box is most likely the cruise control module. The ECM is the larger silver aluminum case.

For wiring go over to the diy-efi.org site, GMECM, under ECMS. Stock your ECM will be the 1227165.

RBob.

 

I have the same problem with my car 1989 iroc 5.7 were u able to solve the problem.

 

Yes but I feel stupid - someone pulled the engine service lamp. now it works fine.