Service engine light

service engine light is coming on when load is applied to 1995 3.4 v-6 engine in chev. sedan. Had codes read and trouble code P1640-QDM-1 Failure was read. Any suggestion,vechile starts and runs find no rough idle.??

Reply to
Travelsmart
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service engine light is coming on when load is applied to 1995 3.4 v-6 engine with 64k miles in a chev. lumnia sedan.service engine light is off at idle rpms. Had the codes read and trouble code P1640-QDM-1 failure was read.Tried dis-connnect of battery to see if computer would clear code with no luck Any suggestion,vechile starts and runs find no rough idle.??

Reply to
Travelsmart

telling us what the definition of a P1640-QDM-1 is would help...

--Don Don Byrer Instrument Pilot Commercial/CFI Student Electronics Technician, RADAR/Data/Comm @ CLE Amateur Radio KJ5KB

"I have slipped the surly bonds of earth; now if I can just land without bending the gear..."

Reply to
Don Byrer

Quad drivers are power integrated circuits typically used to drive solenoids, relays, etc. They were manufactured by, IIRC, Allegro Semiconductor, Inc. for GM products. The early versions weren't short-circuit protected; hence, you read in shop manuals from the

1980s/early 1990s to replace the ECM if a short is found in, for instance, the idle air control motor (replace IAC motor and ECM).

Later QDMs are short-circuit protected and monitor the output to see whether a commanded electrical signal (logic 0 or logic 1 -- power, of course) actually occurred.

I do not know the details of the problem, below. The DTC suggests either a short or an open in the driven circuit. If the owner doesn't have access to a factory shop manual, something like Mitchell's ON-DEMAND will be useful (it's often available at public libraries).

Hope this helps,

Bohdan

D>>

bending the gear..."

Reply to
Bohdan Bodnar

Regarding engine service light was told to Clean Contacts at the PCM connectors to start.However, have no idea where they are located on engine any help here?

Reply to
Travelsmart

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