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No signal PCM diagnostic port


spenser
05-10-2010, 07:35 PM
2003 Trailblazer with 4200 engine. A friend changed the thermostat on his and he didn't disconnect the battery. Just moved the alternator out of the way. Now there is no signal at the diagnostic port. Is the PCM attached to driverside of engine? Pic would be nice. Also can somebody tell me what pins would show voltage at the diagnostic connection?

Wiring diagram would be great!

MT-2500
05-11-2010, 10:51 AM
2003 Trailblazer with 4200 engine. A friend changed the thermostat on his and he didn't disconnect the battery. Just moved the alternator out of the way. Now there is no signal at the diagnostic port. Is the PCM attached to driverside of engine? Pic would be nice. Also can somebody tell me what pins would show voltage at the diagnostic connection?

Wiring diagram would be great!

Check your fuses.
http://www.troublecodes.net/OBD2/

OldSVTGuy
05-11-2010, 08:56 PM
The PCM is the aluminum box with three major wire bundles attached on the driver's side of the intake manifold. Like was earlier stated, better check fuses first.

The Roadie
05-28-2010, 09:49 AM
If the problem is that a scanner doesn't work when plugged in under the dash, it's almost always the CIGAR fuse under the hood. The OBDII connector shares power with the main cigarette lighter. Not mentioned in the Owner's Manual at all because GM doesn't respect the owners enough to use the port.

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