CCM not reporting PCM codes on '95

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Jan 21, 2005 | 02:10 AM

JayH

Thread Starter

Racer

Joined: Sep 2002

Posts: 317

Likes: 1

From: Maple Valley WA

CCM not reporting PCM codes on '95

So, I grounded pin 12 on my 16 pin DLC and can read all CCM, DERM, and what?ABS codes off my '95s dash. But no way can I get the 4.1, or 4.anything for that matter. Any idea why she skips straight from 1.x to 9.x and A.x ???

Thanks,
Jay

Jan 26, 2005 | 03:47 PM

Blower91

Instructor

Joined: Aug 2004

Posts: 108

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Quote:

Originally Posted by JayH

Apart from not reporting DTC, does it appear to work as it should? No other obvious fault?

If everything "looks" OK, I would disconnect a sensor so I know at least one DTC is active. I'm not very familiar with the 95 but would not disconnecting the TPS and turn the ignition on set a code and flash SES? If you are sure at least one code is set in the PCM and the CCM does not report it, I would try a scanner (eg Datamaster) to see if it is able to retrieve any DTCs.

Hope this helps!

Jan 26, 2005 | 08:05 PM

JayH

Thread Starter

Racer

Joined: Sep 2002

Posts: 317

Likes: 1

From: Maple Valley WA

Yeah, I finally had to go to Datamaster to pull the codes I knew were set. Looks like a bad o2 sensor; I would have needed Datamaster to lead me to that conclusion that quickly anyway but it bothers me that the CCM/ECM doesn't work as the service manual (and others) say it should...

Thanks,
Jay

Jan 27, 2005 | 10:10 AM

Blower91

Instructor

Joined: Aug 2004

Posts: 108

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Quote:

Originally Posted by JayH

Good Datamaster managed to pull the codes. Strange that the CCM fails to do that... I thought that the CCM pulled the codes from your PCM the same way Datamaster does and also that Datamaster connects to the same wires as the CCM and PCM communicates, anyone out there knows if this is the case?

Since Datamaster is able to pull the codes from the PCM I would think that the PCM is OK. At the same time the CCM is able to pull the codes from all systems but not the PCM. I would then guess open/short circuit on the serial communication wire between CCM and PCM but Datamaster is able to communicate with the PCM... hmmm, do you know if the PCM or the CCM has been replaced? Do you have the right PCM and CCM for your Vette? Is the instrument cluster (gauges, lamps etc) working as it should?

Jan 28, 2005 | 02:54 AM

JayH

Thread Starter

Racer

Joined: Sep 2002

Posts: 317

Likes: 1

From: Maple Valley WA

Quote:

Originally Posted by Blower91

hmmm, do you know if the PCM or the CCM has been replaced? Do you have the right PCM and CCM for your Vette? Is the instrument cluster (gauges, lamps etc) working as it should?

Don't know about replacement, but I doubt it - everything works fine except for this one little quirk. The FSM states that if the CCM cannot communicate with PCM, etc it will report an 'Err' in the speedo (odo?) section of the dash - I'm not getting even this. Oh well.

Thanks,
Jay

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