Repair shop questions.

Snacks41

New Member
Sep 14, 2014
9
3
3
Hampton Roads, Va
My sister has a 1998 Chevy Venture with a 3.4 Ltr. I usually worked on this in the past because it is similar to the GN 3.8 Ltr. She has an issue now where the car cuts off when it warms up. When this happens it does not start again until it cools down.

She had it towed to a repair shop because I dont have the time to work on it at the moment. For 2 weeks the repair shop kept telling her they dont know what the problem is. They told her it might be Crank Sensor or the ECM. I told her I think it's the (ICM) ignition control module. When these modules get old the material inside breaks down and softens causing the module wires to short out. I found this out on my GN a few months ago.

The repair shop changed out the crank sensor anyway which did not fix the problem. They want here to pay for the new crank sensor and labor. I told her that she shouldn't have to pay because this did not fix the problem with the car cutting off. She talked to the repair shop manager. The manager told her they would not remove the part and she has to pay for it.

Now the story is that she needed the new sensor.

Now my first question is why did she need this new sensor?
The car starts and runs great with no problems, until the car warms up. Then it will shut off. After it cools down it will start up again. This is with the old crank sensor. They put the new crank sensor on and it has the same problem.

My second question is should she have to pay for this sensor?

My last question is what else besides the Ignition Control Module would cause the spark to stop when the engine is warmed up?

Respectfully,
Chris A.

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grass doctor

Well-Known Member
Sep 21, 2018
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saint augustine fl
well hard not to get involved in that , ask them if the car is fixed with their solution ... NO so say ill pay for the new sensor and half the labor , and thats it because it is not fixed and ask to pick up car and tell them you will be taking it elsewhere MORE THAN FAIR seee what they say
 

Snacks41

New Member
Sep 14, 2014
9
3
3
Hampton Roads, Va
Thanks for the replies! I will be going down to the repair shop in the morning. They said they cant find the reason it is shutting off. She even told them I recommended they replace the Ignition Control Module. They still want to charge her $300 for doing the crankshaft sensor. The new crankshaft sensor had no effect at all. I will give an update tomorrow.

Respectfully,
Chris

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LC2 ROD

The original LC2 ROD
Nov 4, 2002
375
5
18
So Cal
Crank no start condition missing spark could be IC module or crank sensor, both are common. Scan tool data should clear that up, no cranking RPM would lead me to the crank sensor or wiring to , cranking RPM would lead me to IC module. Injector pulse is another way to check, crank sensor fault, no injector pulse, IC module fault, injector pulse is still working most of the time.
Use to see these all the time, not so much anymore.
Anyway, Ive probably replaced more crank sensors than IC modules.
The tech could have looked into a little better, IMHO.
 

Snacks41

New Member
Sep 14, 2014
9
3
3
Hampton Roads, Va
Update!
I went down to the shop and the bill was around $330.
I asked what was wrong with the original crank sensor?
He said it was bad and needed to be changed.
I then told him the Car started fine and ran fine. When it got up to temp usually around 15min or more the car would cut off and then you would need to wait about 20 to 30min before it would start again.
I then asked for the old sensor, but he said we threw it away. I asked did the sensor fix the cutoff problem. He said no. I said then why should my sister have to pay for a part that did not change anything?
I said a good tech would be able to use a diagnostic machine and tell if there is no CKP signal.
I then said she's not paying for it. He said I needed to talk to the manager (who was standing behind him).
The manager who I worked with 22 years ago ( yes I used to work there) said "I ain't going to argue with the man just take it off the ticket.
They took off the Crank Sensor and labor about $180.
They would not take the diagnostic fee and electrical check.
Then he told us as we are leaving it was the ECM that was bad.

I dont know why he refuses to believe it's an ignition control module.





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Snacks41

New Member
Sep 14, 2014
9
3
3
Hampton Roads, Va
Update:
I hate to say it! I was wrong about the ignition control module but, the shop was wrong about PCM. I also changed out the PCM with no change. The car dies exactly when the PCM shows temp of 226F.
I noticed fans attempt to turn and that's when the engine dies. I turned the AC on and fans do not come on. I put 12V directly from battery to both fans and they ran.
Driver side fan bearings are noisy and blade does not spin as freely as it should.

I ran car to about 200F and put 12V to fan and car immediately died. I did this twice. I then replaced cooling fan 1 and 2 relays with spare ones. No change.

List of parts changed.
Crank sensor.
Ignition control module.
PCM
Cooling fan Relays

I have attached a diagram.

Any help would be appreciated.

I never saw anything like this before. I am leaning towards the fan loading down the PCM through the fan controller.
I am also trying to figure out why AC does not turn fans on also. I know there is a freon leak and compressor does not turn on. Will that cause fan to not operate in AC mode?

Again thanks for any help.


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salvageV6

Daily Driver
May 25, 2001
14,992
407
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Connecticut
Post the power distribution cell 10 diagram.

Generally the fans are pressure controlled switches, need the A/C fan control diagrams to be sure, so with no freon no pressure no fans...
 

Snacks41

New Member
Sep 14, 2014
9
3
3
Hampton Roads, Va
Post the power distribution cell 10 diagram.

Generally the fans are pressure controlled switches, need the A/C fan control diagrams to be sure, so with no freon no pressure no fans...
Thanks for the feedback!

I was just reading up and I believe you are correct. I just went out and started the van and warmed it up some and disconnected driver side cooling fan while running. The car immediately cut off. Is this normal? I have disconnected fans before but on older cars pre OBDII. I think the PCM has to sense the fans. I cannot restart van until fan is plugged back in. It's got me thinking the fan might be faulty causing an electrical open circuit when initially trying to run.


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salvageV6

Daily Driver
May 25, 2001
14,992
407
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Connecticut
Would probably need the entire PCM pinout to see about that, if the car died removing the fan I would think it would set a code or two?

Could also be a ground issue at splice 105 ect. but would need to see cell 14 for that.

I don't see any feedback to the PCM from the fans in that diagram, the PCM only runs the relays. Need more diagrams....
 
Apr 20, 2017
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I looked into my GM Connect and there are a few TSB's that could possibly relate to this issue. Mostly electrical. Give me the last 8 of the vin so I can narrow it down. In the meantime make sure wiring harness under drivers seat isn't shot and that the wiring isn't getting hung up in the brake pedal. Also wiring connector at pcm.
 
Last edited:
Apr 20, 2017
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Make sure everything under the hood is bolted down for a proper ground. It's hard to follow the bullitans because I obviously don't have the vehicle to hook up the scan tool. Once I have the vin I hope it narrows down the known issues.
 
Apr 20, 2017
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12
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Would probably need the entire PCM pinout to see about that, if the car died removing the fan I would think it would set a code or two?

Could also be a ground issue at splice 105 ect. but would need to see cell 14 for that.

I don't see any feedback to the PCM from the fans in that diagram, the PCM only runs the relays. Need more diagrams....
 

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Apr 20, 2017
53
12
8
36
Post the power distribution cell 10 diagram.

Generally the fans are pressure controlled switches, need the A/C fan control diagrams to be sure, so with no freon no pressure no fans...
Ask and you shall recieve. I just grabbed what I thought you might need. If I'm missing something let me know I can pull it up.
 

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Street Lethal

Tech Anarchist
Oct 8, 2006
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I hate to say it! I was wrong about the ignition control module but, the shop was wrong about PCM. I also changed out the PCM with no change. The car dies exactly when the PCM shows temp of 226F.
I noticed fans attempt to turn and that's when the engine dies. I turned the AC on and fans do not come on. I put 12V directly from battery to both fans and they ran. Driver side fan bearings are noisy and blade does not spin as freely as it should.
Sounds like a voltage spiking issue in conjunction with a bad charging system. The A/C pressure switch would more than likely be causing the lack of both fans turning on when the A/C is turned on, whether by missing pressure from leakage, or a faulty/dirty/corroded switch/terminal connector. But that sounds unrelated with the original complaint and more than likely just a coincidence. Pretty sure these systems keep the fans triggered during restart if the coolant temperature is still within the cooling threshold, which may be why it won't start back up until it is out of that threshold and cooler. Once you applied 12 volts to the fans at only 200 degrees and stalling (original complaint was the stock 226 degree fan trigger) this would point to a bad/weak alternator. Add to the mix a fan that may be having resistance issues and not spinning freely. I would get the alternator checked out (it's a free service) and perhaps replace the actual fans to see if this fixes the issue. The only area that I question is the disconnecting of the fans and the engine not starting, I don't remember if my old 3.4 Camaro did that when I had it back in the day. If that is the case, it might have something to do with that "Ground Distribution Center" in the schematic, but I am not positive on that....

- Rob
 

salvageV6

Daily Driver
May 25, 2001
14,992
407
83
63
Connecticut
I would start by changing out the third coolant fan relay labeled coolant fan relay (no number.)

I believe it should be a different part number from the other 2.

The fans run in series at low speed when Relay 1 kicks in PCM controlled.

At the high temp. 226 degree point they run in parallel each getting a full 12 volts and all 3 relays have to work properly PCM controlled.

There doesn't appear to be any feedback to the PCM from what I can see.