Chevy Impala & a GMC Jimmy
Dying on the highway and a 4WD shifting problem.
This weekly Q&A session answers your questions about cars and trucks. This week explores a 2000 Chevy Impala and a 1999 GMC Jimmy 4WD problem.
Question: 2000 Chevy Impala
Hello:
I own a 2000 Chevy Impala; it has 240,000 kilometers (149,128 miles) on it. The problem is that it stalls when driving down the road. It was first discovered when driving on a 4-lane highway and the car just stalled and I had to pull over very quickly (quite dangerous!!). I took it to a dealership in Toronto and they did a diagnostic test and said nothing showed on the diagnostics. Took it to a dealership where I live and they said it was the Mass Air Flow sensor and they replaced at a cost of $600.00. When I picked it up it stalled again on the highway on the way home. That did not fix the problem. I was not pleased!!!
They put a flight recorder in my car to record when it stalls. I did that and took it back, however, now they say they do not know what it could be and have given me a variety of reasons with a lot of extra cost involved.
What is up with this car? It has been a great car until this... Is the car ready to be taken to the dump? I cannot drive this car like this at all... especially not on a major highway.
Any suggestions?
Thanks,
Sue Tasker
Answer:
A problem like this can be difficult to diagnose since when you bring it in everything will check out as good. The problem can only be diagnosed when it manifests itself.
Sometimes with a problem like this it is a good idea to keep a log documenting the conditions under which the problem occurs. For example; how long you've been driving, ambient air temperature, driving conditions, does it sputter/cough and dies, dies like turning the key off, how long does it take to restart etc. There is no such thing as being too detailed. This log could give an experienced technician enough information to make a better, informed diagnosis.
As it stands now the most likely problem is the Ignition Control Module (ICM). Very often as an ICM gets old they become heat sensitive. When they get too hot they stop working, causing the engine to die like turning the key off. There is a heat conductive grease between the ICM and it's mounting, underneath the ignition coils, that helps transfer heat away from the ICM. Over time this grease dries out and is no longer effective.
Removing the ignition module, cleaning the old grease off and applying fresh grease may improve the condition. If it does that would support the case for a bad ICM.
Question: 1999 GMC Jimmy
I have read you article from this date about the "1999 GMC 1500" 4WD that won't shift in and out of 4WD". I have the same problem. I ran the procedure you detailed and observed all 3 lights flash twice then repeats until the pin 13 is ungrounded. Can you tell me what this code means - Encoder motor or TCCM Module?
When I press the 4HI Button nothing happens but, when I press the 4Lo Button both Hi & Lo Buttons flash in an alternating pattern and there is a clunk from the transfer case but it does not engage.
My Vehicle is a 1999 GMC Jimmy with the NP1 (NP233) Transfer case and has had an odd behaviour since new. It will engage the 4-wheel drive at highway speeds (60-70 MPH) after about 2 hour of Interstate Driving.
My local dealer is of no help in anything concerning this vehicle, as I did not purchase it there.
Answer:
DTC 3 indicates a fault in the TCCM Motor Circuit. Here is the troubleshooting procedure for that DTC.
That's all for this week. Feel free to browse the archives for past topics. And, as always, if you are stuck and need an immediate answer you can always call Vince on the phone.
DTC 3 Troubleshooting Part 1
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DTC 3 Troubleshooting Part 2
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