No spark

I have a 2001 Pontiac Grand Prix SE 3.1 litre with the issue of after the car gets up to 180 degrees, it shuts off and doesn’t get spark until it takes it’s time to cool off and then will restart and idle for about 20 minutes and shut off again. I replaced the ignition control module after the car was put on an engine scanner thinking it was getting too hot and telling the engine to shut down. According the the scanner, it was still getting a reading from the crank sensor saying there was still rpms so I was thinking thats not the problem and I am ruling that out for now. I have taken the coils off the module and ohm tested them cold and hot after the car died. That reading was the same on both occassions at 002 ohms at 2000k. I know that there is only 3 things that control the spark to the coil-pack; crank sensor, cam sensor and the ICM. My questions are; Is it possible that the coils have simply tired out and need to be replaced due to 136,000 miles, weak spark and heat issues? Or is the cam sensor telling the module something I don’t know? Because it runs great after it cools off and I can restart it without a miss. Or could it possibly be another sensor some where else that has to deal with the temperature of the engine that is shutting down the engine when it gets around 180? I have completely run out of ideas on this one and am getting very frustrated at this point. I do not want to buy any more parts without a good reason. Already chased enough gremlins because it was thought to be originally that the fuel pump went out. Not the case at all because there’s plenty of gas in the oil now after all the cranking, which is due for a change anyway. So if you have any suggestions please let me know. Freezing in Minnesota, James H.

Check the crankshaft position sensor resistance spec. Now heat the crankshaft position sensor with a hair dryer or heat gun and check it again. You’ll be surprised.


Do you know of a website where I can get that spec?

You forgot the biggie that’s connected to the DIS. The ECM.

The DIS does what the ECM tells it to.

Consider a loose connection between the ECM and the DIS that is aggravated by heat. Any one of those wires in the diagram looses its connection to the ECM and the DIS thinks you just turned the key off.

OK. checked all the wires, nothing wrong there. Replaced the ignition control module and crank sensor. resistance checked all coil packs and got same reading and also switched out each individual coil pack with a new coil one at a time to see if one was bad while car was running. Still the same issue, car runs for 15-20 minutes and then shuts off. I also disconnected the battery for the afternoon and reset the anti-theft by bumping the starter and leaving the key on for 10 minutes. So after the engine cools off it will restart and run for the same amount of time and die again. I’m running out of options here and don’t know where to go next. Any suggestions are greatly appreciated. Thanks. James H

any suggestions? might be ECM next to replace.

Have you checked to make sure the ECU and ignition areas are getting the proper power when the trouble happens? If those areas are getting good power then getting a used ECU may be the next best thing to try out.

You could have a shorted injector. It will shut down the ECM. The 3.1 was known for this problem with injectors. Ohm check each injector, I’ll bet you find a shorted one.

Another thing to do is get the diagnostic A-chart “engine cranks but doesn’t run”, it has the step by step instructions to diagnose this problem when it acts up.

Thank you both very much. I’ve been chasing ghosts for a week now. Did check for power supply issues and they both seemed to be getting good power. Have not checked the injectors yet. I haven’t heard that one until now. Will do that in the morning. Your help is very much appreciated.

By the way- where do you find the diagnostic A-chart?

Remember to check for the shorted injector when the engine is hot and has just shutdown (due to the problem).

Quick question? How do you check the injectors with out taking the upper plenum off?

You might be able to get to the injectors without taking the plenum off, it might be difficult though. In the end you might have to take the plenum off.

The other way is to find the injector harness connecter and ohm check the circuit from there but you have to know that you will be checking the whole circuit not just one injector so the resistance reading will be different. There is a formula to calculate the circuit resistance but I don’t think I can explain it clear enough for you.

Diagnostic charts are available in a service manual or on ALLDATA.

You might be able to check the injectors by testing them at the ECU connection. I’m not sure if your model has some current limiting resistor built inside the ECU for the injectors but it may have. Most systems I think operate the injectors by having the ECU make the ground connection inside the ECU. If yours is that way then you just need to find the common power source lead and then check the individual ground leads to the ECU. You will need to isolate the connections from the ECU and power of course doing a resistance test.

It will be interesting to see if a shorted injector is the trouble here.

I’m doubtful it’s an injector problem but he should at least check them before he replaces anymore parts. In my experience if there is a shorted injector it takes out the quadriver in the ECM and it won’t restart… period. In a case like this replacement of the shorted injector and ECM is required to get the vehicle to run again.

Good Chart! It will show “Downloaded 2 times”. I, hellokit, did that. The chart Part 1 can be downloaded and viewed. Trying to enlarge THIS page doesn’t yield a legible view; so, the OP (vernon) hasn’t availed himself of the information. Too bad.
Part 2, and Part 3, didn’t download. Did you load them?
If someone wants an alldata chart, many (some?) public libraries have an subscription. It’s FREE for a library patron. Said patron can go to their public library (in person) and use the service. I do…hellokit