Mechanics

CAR STALLS WHILE DRIVING, THEN STARTS BACK

2003 Saturn Vue

Computer problem
2003 Saturn Vue 6 cyl Two Wheel Drive Automatic 54600 miles

My car starts fine, am able to drive it for 10 - 15 minutes (approx 5 to 10 miles) and then the engine just dies. Car is going on momentum, SES and CEL comes on, the security light flashes 3 times and then if I press the accelerator, the car jerks back into power and continues on till it stalls again which could be another 5 to 15 minutes, or on some occasions runs fine till next day when it repeats. Dealer pulled code P1629 and said BCM needs to be replaced, but say that may not solve the problem, and they would replace the ECM after that. They haven't stated what they would replace after that. Crank position sensor is okay. Another mechanic said that he does not think it could be the BCM because all the modules seems to be operating okay and communicating with each other. He found the air intake sensor (built into the air mass flow sensor) was bad and replaced it bu that has not solved the problem. He also checked the electrical harness.

My question is if anyone has an idea of what could be causing the intermittent stalling. Also, one the car has started fine and has been running (meaning that the passlock sent the correct passcode to the BCM and the BCM sent the fuel and spark enable code to the PCM), could the passlock system still shut down the engine. This would mean that the passlock is continuously moniotoring the car (not just during starting) even while driving to verify security.

Thanks for any help you can provide.
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Magnumopus
August 13, 2010.





http://www.2carpros.com/forum/automotive_pictures/416332_2003_vue_code_P1629_part1_1.jpg



http://www.2carpros.com/forum/automotive_pictures/416332_2003_vue_code_P1629_part2_1.jpg



http://www.2carpros.com/forum/automotive_pictures/416332_2003_vue_code_P1629_part3_1.jpg



http://www.2carpros.com/forum/automotive_pictures/416332_2003_vue_code_P1629_part4_1.jpg



http://www.2carpros.com/forum/automotive_pictures/416332_2003_vue_code_P1629_part5_1.jpg



I posted the trouble tree for code P1629 if you read the trouble tree it really only lead's you to a bad bcm it doesn't say anything about a bad ecm.Since your problem happens whenever it want's to they would have to keep your car till it happened long enough to follow the trouble tree i posted to tell for sure it was a bad bcm.Here's the bad thing about electronics it will be working perfectly one second then bam it's failing then it could work great for another month.So to give you a answer of what is wrong for sure is not possible it's looking like the bcm though.Especially since the security light comes on when it stall's and won't start.If the bcm is failing then it could stall out while driving.I want you to keep an eye out for other symptoms of a bad bcm like door lock's become inop or key less entry becomes inop fuel gauge reads empty when you know you have gas.inside lights don't work or flash etc.
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Saturntech9
Aug 13, 2010.
Louie,

Thanks for your reply to my question. There are some key differences between what my car is doing and the diagnosis for a bad BCM.

When the car stalls and the security light goes off after blinking 3 times, if I press the accelerator, I immediately have power. So, if I'm driving at 50 mph, and it stalls, speed might drop to 45-40 mph in 3 to 4 seconds and then I have power. Even when the car stalls and dies completely (at lower speeds and if I do not press the accelerator), I am able to start it right back up without any problem by putting the car on park and turning the ignition key. As far as I know the Passlock system checks for security at ignition start time and once the car is up and running, then it enters a safe mode.

In all the posts that I have read about bad BCM and the security module, the people were not able to start the car, or if they started it it died within seconds and they had to wait atleast 10 minutes before they could restart.

I haven't had any issues with either the auto door locks, dash lights, gauges, keyless entry.

Tiny
Magnumopus
Aug 13, 2010.
When it goes into security mode it cut's out the injector pulse's so your engine doesn't get any fuel. There really isn't any set this is a bad bcm symptoms grant it I have seen a a lot of bad bcm's and the thing's they do when they go bad but I haven't seen everything they can do when they go bad. Just when I thought I have then I have one go bad causing something I have never seen. The problem is when the bcm's or any computer in a car goes bad they never tell on them selves unless another computer can't talk to it and set's a code for that which isn't always the case when they fail.I'm really shocked you don't have any other code's with the way it's running. You said the crank sensor is good but it could still be bad another thing that with temp is good one second bad the next.I have seen them do thing's I didn't think a bad one would do. But with your security light flashing and your code p1629 there is something going on with your pass lock wiring or bcm. You could have more then one problem too but your saying that the security light is flashing when this crazy stuff is happening also.I guess the best thing that could happen is that the engine die's and doesn't start at least they could track the problem down that way.I know people hate to hear that I know I would hate to hear it. But being on the repair end of these crazy problem's that come and go I understand that sometimes that's the only way to fix them. Unless you want to start throwing part's at a car till it's fixed like there talking about doing which is going to get real expensive real quick.

Saturntech9
Aug 13, 2010.
I understand the Passlock system is programmed to go into a fail safe mode if the engine is running, which means that the car should not shut down if engine is running (otherwise we'd be having many accidents). In fact, one of the methods adopted to bypass the Passlock is to cut the yellow passlock wire is cut WHILE ENGINE IS RUNNING.

Just some more info I thought might be useful.

Tiny
Magnumopus
Aug 13, 2010.
I don't see how cutting the yellow security sensor signal wire would bypass the pass lock but if you say so. Also I didn't say that a pass lock sensor or it's signal would cause the engine to stall the bcm failing would cause a stall though. Sorry if you misunderstood what I was trying to say.

Saturntech9
Aug 13, 2010.

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