Coves4me

OK, I solved the aftermarket radio issue by installing the resistors and diode and that made the C72 and H72 codes vanish. I jumped the #4 and #12 pins on the connector under the dash and I still get a C42 code in the "A" module, the Derm (airbag) module. This is a non-issue as I could care less about the airbags and whether they work or not. BUT, my brand new OEM cooling fans still run continuously and the Service Engine Soon (SES) light still illuminates continuously with NO other codes showing. I'm puzzled. I've replaced the MAF sensor with a new AC Delco replacement, the ECT sensor has been replaced, the MAP sensor has been replaced, the EGR valve and EGR vacuum solenoid are new, a new AC Delco fuel cap was installed, a new fuel filter was installed, a new fuel pressure regulator was installed, the catalytic convertors have been replaced and the O2 sensors were replaced the Denso types. Now, I've got new AC Delco O2 sensors to install, but there are no codes showing that indicate the Densos are throwing the SES light. Could the Denso O2 sensors be throwing the SES light with no codes? I'm puzzled and could use some help. Thanks in advance.

Mark

C409

..... Buy a Factory Service Manual and follow the diagnostic flow charts ... OR ... keep on throwing parts at it til the dang light goes off ...

toptechx6

I don't know where you are getting your information, but it is WRONG. There is no "A" module, there is however a 4 module and it is the PCM, Look at this link and you will see that DTC 42 is for the ignition control mocule CIRCUIT. That code in your PCM is the reason your fans are running.

http://www.digitalcorvettes.com/foru...56&postcount=9

NOTE: The code 42 does NOT mean you need an ignition control module. You need to follow the diagnostic procedure in the Factory Service Manual to isolate the problem in the CIRCUIT.

Coves4me

Thanks for the replies......BUT, I do have the 1994 FSM (both volumes) and there is a Module "A", it is the DERM module for the airbag system. Now, the C42 code and H42 codes show up AFTER the "A" on the digital dash. This would tend to indicate that the airbag module cannot hold a proper charge to initiate the airbag deployment (according to the FSM). I will check the Ignition Control Circuit using the FSM, but the car idles and runs fantastic, certainly not like it is in "limp home" mode which is why I haven't run the check on the ICM. Also, I've replaced the ICM and coil with new AC Delco pieces. Thanks again for the replies. I'm trying to avoid taking it to the dealership.

Mark

Coves4me

As an update.....I borrowed a buddy's Actron 9145 scanner and tapped into the computer of my car to read and cancel all codes. Well, it told me there were no codes in any modules!!!! So, why is the SES light on. It seems that my PCM is faulty and will need to be replaced. We erased all codes, disconnected the negative side of the battery for 5 minutes, then re-connected the battery and went thru the process again. Sure enough, NO codes, but the SES light was still on. A new computer is on the way!!!! Thanks to all.

Mark

pcolt94

You are right, there is a module A which is the Derm module. Codes can appear, but if they come back after cleared that’s when there could be a problem.

Also you know you can clear the codes without an external scanner. If you have the FSM it will tell you how in the x.7 module.

Delphi (and Delco) is the other brand that works OK in the vetts. Look at post 3 in this thread. It sounds exactly what problem you may have. The O2s may be the cause.

http://forums.corvetteforum.com/c4-t...i-correct.html