no communication between scanner and PCM

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I was thinking of buying a Chevy so I had it checked out by Firestone......
mechanically it was fine, but when the tech. tried to read the scanner for
codes he said nothing came back........ the check engine light never comes
on but all the other cluster lights work fine...... I'm wondering if the
seller unscrewed the check engine bulb, but I don't understand why the
scanner is not able to read anything... if the PCM was bad would the truck
even run as good as it does?   What are the possible reasons for no feedback
to the scanner?



Re: no communication between scanner and PCM
On 8/26/12 1:31 PM, don wrote:
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There would be some possibility that only the output signals from the
PCM to the CEL and/or the OBD connector have gone bad. Rest of PCM
could be functioning OK. You would have to try replacing the PCM to
confirm. I've got them from U-Pull-It boneyards for as little as $20

I would first check all connectors and grounds for good contacts.

Re: no communication between scanner and PCM
don wrote:
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What year? Model? Heavy Duty?
If you plug a lighter in the cigar lighter does it work?
If not then the OBD II connector isn't getting power and the scan tool
won't read.
As for the CEL, it could simply be blown.

--
Steve W.

Re: no communication between scanner and PCM
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Obd 1, 1.5, 2. ??

Greg

Re: no communication between scanner and PCM
2

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