no communication between scanner and PCM

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?

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On 8/26/12 1:31 PM, don wrote:

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.

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don wrote:

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.

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Obd 1, 1.5, 2. ??

Greg

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2

wrote:

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