mffi115

I know this should probably stay in the Scan and Tune but I posted this question in the Scan and Tune and got only one response listed below so I posted here. It seems not too many folks cruise that section of the forum. Any way here's my question below with the reply and an update from me.

Any help??

My '94 LT1, 6SPD w/90K miles is showing codes:

C 31/33/35/37

When I clear the codes they come back, and, of course along with the history codes.

The User's Manual for the grounding plug diag kit I have states these indicate:
data circuit shorted to B pos or CCM drive open (C31)
data clock circuit shorted to B pos or CCM drive open (C33)
data strobe circuit shorted to B pos or CCM drive open (C35)
M clock circuit shorted to B pos or CCM drive open (C37).

So what does this mean to a knuckle dragger like me and what can I expect when I access the CCM, and how the heck do I fix it? Could this indicate a loose/bad connection where ever this B pos thingie is, CCM drive thingie, or does the CCM need to be replaced.

My Heims was pretty clear that the CCM itself rarely fails and that loose/bad connections are the usual suspects. I have had an occasional, sporadic flickering of the dash/speedo lights leading up to this and it's still there.

Thoughts, ideas, opinions? Help!

Thanks,
Carl

RESPONSE FROM: Vis Croceus
CF Senior Member



This is probably going to be a bitch to track down.

I'd start diagnosis from the cluster end rather than the CCM. Much easier to get to.

This "B pos thingy" is 12V.

[edit]Actually, I just checked this in the FSM, and the diagnostic charts for these DTCs tell you to diagnose from the cluster end. Just follow those charts.[/edit]


MY REPLY:

Thanks. I assume by cluster end, you mean the instrument cluster (speedo, etc.)? I told you I'm a knuckle dragger. Is this a volt meter or visual type task?

MY UPDATE:

This problem seems to be intermitent I haven't been able to work on this problem due to my traveling. Yesterday, I checked for the codes, - none, took the car for a long ride and checked again - got the history codes, cleared them and got C12. What gives?

Does this sound like a loose connector or the CCM giving up the ghost?

We're moving and I will be taking it on a 2,500 mile trip. Can I let this go? I need to spend the time packing up our stuff and might be forced to take it our for service.

Tom Piper

The CCM drives the intrument panel display -- in other words, it is the brains behind what is displayed on the digital section of the instrument panel.

My guess would be an open somewhere in the wiring/CCM.

If I were doing it, I would check the connectors at the instrument panel first, and then the connectors at the CCM.

Tom Piper