Hi all, quick update:
The new ECM didn't fix the problem. I did come across this though, seems like it might be the problem I am having: http://answers.yahoo.com/question/in...4065850AA81UMn
Given this, I ordered a completely new fan assembly including new fan motors. I will install this weekend and report back. I've been driving the car around with just the passenger side fan running and it's not overheating at all. I could probably drive around forever like this, but the problem really gets to me. I just want to fix it!
The new ECM didn't fix the problem. I did come across this though, seems like it might be the problem I am having: http://answers.yahoo.com/question/in...4065850AA81UMn
Have seen this before on Malibu, Impala, Oldsmobile, and Buick full size in those years. One good place to check is the radiator cooling and condenser fans. They are two fans behind the radiator and sold as a complete assembly. What you usually find is that one of the fan motors has gone bad and is either shorting out, or turning slower and arcing inside the motor. What this does is put a voltage surge and static into the electrical system that the computer cannot handle. It causes the GM computers on these cars to go haywire. Causes the exact problems that you are describing and sometimes different symptoms such as AC compressor going off and temp guage suddenly reading either totally hot, or totally cold when that is not hte case. Turning off the car often resets it for a bit and in the case of the ac compressor and some other symptoms removing the battery or power to the computer for 10 minutes or so causes it to often work fine for a day or so. However the cooling fan motor being defective means that it will soon do it again, often in a few minutes of drive time. We have changed out many of these cooling fan assemblies. I know that you mentioned the fan inside not working, but that is not the fan that is defective. It is only a symptom of the problem. GM has had tons of problems iwth this very thing and if you read the forums on Impala and Malibu in particular you will see all sorts of attempt to correct this that usually involve changing computers, etc. Computer is normally not defective. It is simply unable to handle the voltage surge and static from the bad cooling fan. The cooling fans are most often to blame and because even the defective cooling fan motor often continues to run (though at a reduced speed) it is usually completely overlooked. Because there are two fans at the radiator, even with one still running the motor usually won't overheat unless severe hot weather. that is why often folks never even look at that for the problem. I bet that if you have the radiator fan assemblies checked you will find one of them bad. Sold as complete assemblies from the dealer and just over 200 bucks if memory serves. As far as I know cannot buy individual motors or parts but only the entire assembly. After replacing, if they are bad, be sure and remove power from the computer for 30 minutes to clear out the stored problems and it should work good. There are many other electrical problems with those cars as well, but we have found that this particular problem has caused almost all the "computer or wiring" related problems that we have seen with these cars as other than that they are relatively dependable in use. Good luck regardless and hope you get it fixed soon.
Given this, I ordered a completely new fan assembly including new fan motors. I will install this weekend and report back. I've been driving the car around with just the passenger side fan running and it's not overheating at all. I could probably drive around forever like this, but the problem really gets to me. I just want to fix it!
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