I have an 89 Iroc with the L98. It has the dual coolant fans. When I first start the car the primary fan runs for almost 30 secs and then turns off. It comes on and off normally then during regular driving. There is no SES light on, and I have looked for codes but found only code 12 which is normal.

 

ROC,

Does the engine start and run easily when cold? I'm thinking you might have a CTS that is "flipping out". It may also be a CTS wiring problem, but that shouldn't change when the engine warms.

That IS a strange one you have there...

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Later,
Vader
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Justice and Freedom will Prevail

 

The engine runs fine but shakes slightly at idle but nothing bad. I replaced the CTS with a GM replacement and the wiring looks good. The car has 62K miles on it. Also the car has the ARAP prom in it with nothing else done with it except to reverse the fan turn on logic, but I dont think that would make a difference. It seems as though it is some sort of diagnostic for the fan??

 

BTT

 

My '89 has done this since new, two or three different PROM updates, one different ECM and a different CTS, all for different problems, but this "problem" has always been there, off and on. Sometimes when the engine is stone cold from sitting all night, and other times after a warm start.

My fans only stay on for maybe 5-10 seconds max, if I recall.

 

Now that I think about it, it is really only about 10secs that they stay on. But that is weird???? Maybe its an '89 thing??? But it never did this before I put the ARAP chip in?????