gm codes


Old 06-18-02, 05:55 PM
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gm codes

92 olds cutlass supreme. running kind of rough. seems like an exhaust problem (maybe egr valve) so i thought i'd check the codes. i have one of those little metal tools that jumps the a and b terminals to give the codes up. works great except all i get is code 12 which just means that the diagnostic terminal is in fact grounded. no other codes appear even after waiting awhile (code 12 just keeps coming up over and over).
now, i know for a fact that there's other problems (for example, i unplugged the tcc solenoid a couple months ago) so my question is why aren't any other codes coming up?
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Old 06-18-02, 09:28 PM
Join Date: Mar 2002
Location: Louisiana
Posts: 438
If it wasn't run long enough to get to temp, you did not get to closed loop operation and the computer normally won't set a code till then.
If you've disconnected the battery or pulled the wrong fuses since you pulled the TCC sol., you would have cleared the code.
Unplug the EST connector run it to temp, you should get a code.
What is your engine size??? Does it run rough all the time? Give more info for better help from these guys.
Old 06-18-02, 10:48 PM
Join Date: Dec 2001
Posts: 2,538
disconnecting the tcc solenoid on most gm's will not usually set a code in the computer, there is lots of things that can cause an engine to run rough that will not be computer or sensor related so i would check those first, such as fuel pressure, ignition system, coils, plug wires, and sparkplugs, any vacum leaks.
Old 06-19-02, 03:46 AM
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I agree with BeJay. Always start with the basics before throwing parts at the problem. It will soak you in a jiffy that way.
Old 06-19-02, 09:08 AM
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yep, i sure do realize that many things could cause poor running which is why i thought it'd be easier to get the codes and let the car tell me what's wrong.
as it turned out, a bad vacuum line to the canister purge valve - why that didn't give a code i have no idea.
Old 06-19-02, 09:10 AM
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Because the CPV in that year is vacuum, not computer regulated.

The codes will only show for what is computer related.

A bad spark plug would not likely show up with a trouble code on an OBDI car.

That is why the basics are often overlooked in automotive diagnosis .

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