Unable to connect to pcm - Chevy Impala SS Forum
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post #1 of 6 (permalink) Old 04-16-2012, 04:55 PM Thread Starter
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Unable to connect to pcm

I recently had issues with my transmission on a 95 impala. I wanted to rule out everything before pulling the trans so I tried to connect to the pcm and run live data. The scanner was unable to connect to pcm. I tried pushing the wires on the back of the connector to make sure there was contact . I also checked cigarette lighter fuse and fuse under the hood on the passenger side. They were good. After that, I pulled a pcm from a 95 caprice at the junkyard and dropped it in. I was still not able to connect to the pcm and still don't have second and overdrive. I've been working at this for a few weeks and I am close to doing something crazy like putting her up for sale. Any help is appreciated.
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post #2 of 6 (permalink) Old 04-16-2012, 05:54 PM
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Have you successfully scanned before ? What setup and software are you running ? Can we assume you plugged the pin into the correct socket ? Is it also safe to assume that by "live data" you aren't referring to the D900 live PCM data code reader, which is OBD2 only ?

Generally, being unable to connect to the pcm is a result of:

1) Having the wrong com port selected; or
2) If using a serial to USB adapter, having an unsupported model.

1996 Roadmaster Wagon
1995 Caprice Wagon
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post #3 of 6 (permalink) Old 04-16-2012, 08:48 PM
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Unable to connect to pcm

When I faced this situation,I ended up running a new single wire from the data link all the way to the PCM ,problem solved. I still don't know where the "open" is,but it doesn't matter.
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post #4 of 6 (permalink) Old 05-12-2012, 09:21 PM
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Get a hold of EagleMark if the problem persists. Hes awesome with PCM's

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post #5 of 6 (permalink) Old 05-13-2012, 09:06 AM
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No second and 4th indicates an issue with the band in the trans or one of it control pieces like the piston and accumulator on the side of the transmission. Its possible you chopped a seal or cracked a piston in there. Look through the stickies in the drivetrain section for further troubleshooting. As far as the scanner not communicating, what brand and model number is it?


94-95 Scan. Free, well written diagnostic software
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post #6 of 6 (permalink) Old 05-13-2012, 10:47 AM
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most likely 2/4 band is done

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