Check all your ground connectionsunder the vehicle because it seems like you have power going to systems because it does on and off intermediately and it seems to be a ground curcuit problem if anything. and check them all there are a lot of them everywhere. be careful and to use a digital volt meter. do not give up cause you will find it[sm=drlove.gif]

 

This thread discusses a bad PCM as the root problem ... will that also cause other "electrical gremlins" to surface?

I also have a 93 DeVille showing a "c" in the CCC. Just started last week, the a/c turns on even when it is switched off. Also, when I start the car, the a/c usually comes on, temp set at 75, and then a few minutes it will go blank and show the "c".

Will the PCM also cause the Fuel Data Center to not display? It comes and goes, but usually will not reset, just not display.

Any help would be appreciated.

 

c is for clock which bcm has more control of. Are codes set?

 

I cannot get the codes to come up. Unless I am trying to access them incorrectly (hold off and warm at the same time), it will not enter the diagnostic mode. Any suggestions?

 

What happens when off and warmer are pressed? Do all the buttons on a/c panel work?

 

Actually the buttonsdo not workmost of the time since this issue started. Sometimes when I start the car, the CCC works, then will revert to the mode where the "c" appears. Other times when I start the car, the "c" is there and the CCC doesn't respond to any buttons pressed.

 

Got codes to come up. I am getting
E47 E85 F30 F31 F40

I cannot determine what the F codes are. Any suggestions?

 

E47 - BCM-PCM DATA PROBLEM
E85 - THROTTLE BODY NEEDS CLEANED
F30 - CCP-BCM DATA PROBLEM
F31 - FDC-BCM DATA PROBLEM
F40 - AIR MIX DOOR PROBLEM

This condition is not an easy fix if you don't have FSM or parts car to raid parts from. You could try to unplug different components when condition occurs, a see if corrects itself indicating bad part.

I suggest to disconnect and re-connect if no change:

1) a/c programmer
2) FDC - fuel data panel
3) CCP - a/c control head
4) PCM / ECM
If disconnecting the different parts make no change BCM is the likely cause. If you have or can get access to a FSM follow diagnostic charts.