What is causing my vehicle to shut off while driving?

11522SP

MEMBER
2008 SATURN VUE
V6
2WD
AUTOMATIC
131,200 MILES

Hi, can anybody assist me until I can get another diagnosis, please? Yesterday I had an ECU module replacement and programmed for my car listed above XR. It was diagnosed twice by two different auto shops prior to getting this done, but both ruled out that it needed to be replaced to prevent the disconnect and shut down. A week or two prior, the alternator was determined to be the issue, so it was replaced with a newer one even though this one was 6 months old. So, when the ECU module was programmed and replaced yesterday, I drove not even halfway from the auto shop and my truck shut down on me while I was driving. The starter is less than a year old if not a year yet. The battery was said to be good enough, and there had been some codes about the bank 1 sensor 2 needing replaced? Can somebody help? Thank you

5 Replies

AL514

MECHANIC
4,675 POSTS

Hello, Do you know exactly what those code numbers were, they sound like oxygen sensor codes. But those codes might give us some direction. So what exactly is happening, is the engine just shutting off in the middle of traffic or cruising down the highway? Does it take a certain amount of driving time before this happens and does the check engine light come on just before it stalls out? Usually in a case like this its something like the crankshaft position sensor getting hot and cutting out. Since it sounds like you are able to restart it and keep driving after some time, correct me if im wrong. But a failing sensor will do that. Once it cools off enough it will restore the signal and the vehicle will start again.
Im not sure what shop youre bringing it to, but are they able to reproduce the problem at their shop or are they just changing parts in a hope that it will get fixed? Because replacing a computer (ecm) is a last resort, and even then we would need to fin out why it failed to begin with. I never replace an ecm without finding a cause.
Do you own a small scantool or any diagnostic equipment?
Also the engine shutting down has nothing to do with the Starter, but if you can call the shop and get the exact code numbers that are appearing that will help us figure out whats going on here. But more than likely it is a sensor failure,
I will get you the wiring diagrams for the crank sensor circuits, but if you dont own any tool, I would recommend you at least get a basic multimeter. One that can read 20volts DC. Even a very basic one from walmart will do. We're only working with a 12volt system, I will also go though the Technical Service Bulletins for any information.
One other thing, do you have anything plugged into the charging ports inside the vehicle, any bluetooth items or anything like that? You dont have any of the items below in your car? Even USB charging devices..

https://www.2carpros.com/articles/crankshaft-angle-sensor-replacement

https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor

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Thursday, May 5th, 2022 AT 11:30 AM

11522SP

MEMBER
3 POSTS

It does exactly what you are describing. It randomly shuts down/off while driving and in traffic or just in general when it's on, but I don't know the exact minute it will, but when it's about to the light that is on that lights up the dashboard flickers/fluctuates and the truck sounds like it is overheating, then it shuts down at any given moment. When I'm driving and it about to do that, when I make a turn and use my flickers, have music on, roll up and down the windows, it's like a shortage or something is going on and then it makes a noise like it's about to stop and or stops and resets and resets multiple times etc. At times it delays starting as well. Yes, I have a tool which is the one from fixed. It shows me the same codes, says third misfire, and has the O2 sensor codes up there. And says the impact is major, vehicle isn't drivable, get fixed immediately. The check engine light stays on as well as the ABS light/traction light and light for tires, the light/sensor for the tires was replaced a couple years ago though. The codes that pop up from the fixed device are: HOS2S circuit high and low voltage bank sensor 1 sensor 2. Codes: PO137, PO138, Signal stuck rich P2271 and Cylinder Misfire PO303. The auto shops said the machines they used were saying it was the ECU module and the sensors weren't the issue as to why my truck shutdowns.

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Thursday, May 5th, 2022 AT 12:58 PM

AL514

MECHANIC
4,675 POSTS

Okay, so, the instrument cluster flickers, and are you saying that using the turn signals, or one of the window switches or making a turn causes the fault to occur? Or are you losing power to those components during the fault? I'm just trying to get a clear picture of this happening.
If this is happening during a turning of the vehicle that's a good indication.
The reason your tool is having a major impact is because this is effecting one of the catalytic converters.

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Thursday, May 5th, 2022 AT 1:26 PM

11522SP

MEMBER
3 POSTS

Both of what you said, but it does what you said before it shuts off completely it’ll play around if it doesn’t completely shut off. But yesterday when it shut down, it just shut down completely without the flickering/fluctuations starting first, then when it did cut back on and I didn’t have to restart the truck to turn back on, it started flickering until I got home. Then when I got home it was flickering like it was about to shut off, but it didn’t shut off completely again but still flickering. While it was on, I hooked up the fixd device and it had the codes up there that I mentioned.

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Thursday, May 5th, 2022 AT 1:59 PM

AL514

MECHANIC
4,675 POSTS

Okay. Well, since you are getting these codes together, (p0137 and p0138) which are "signal lower than 0.050v (50mv) for more than 2 min" and "signal higher than 1v for more than 1.5 minutes" I think you have a wiring issue, where the wiring harness is contacting other parts of the harness at different times, for example, for the 02 sensor to read less than 50mv for over 2 minutes, it must be shorting to Ground. 50mv is pretty much nothing. This is the same for the other code as well. For the 02 to read over 1 volt for that amount of time it must be shorting to a power wire somewhere. The criteria states 1v. But that's only the setting criteria, it could very well be 12 volts and it would still set that same code, because it's over 1 volt. I would go under the truck and inspect the wiring harness for the 2 oxygen sensors that are after the catalytic converters. Those are the bank1 sensor (2) sensors. The Bank 1 Sensor 1 are the sensors before the converters. So, there might be a spot where the wiring harness for one of the back sensors has possibly melted and touched the exhaust pipe.
Or one of the connectors for the back 02 sensors has corroded really bad and is shorting out to the heater circuit. All 4 wires for each 02 sensors are in the same connectors for each 02 sensor. So, it can easily short to power and to ground at certain points, turning a corner, or when the harness moves due to vehicle movement. My information is stating that Bank 1 sensor 2 is on the passenger side, after the converter, So check that part of the wiring harness first. The sensor is screwed into the exhaust pipe, Find the sensor and check the wiring for it all the way up as far as you can towards the engine.
Honestly I have no idea how the shop you had it at can say it's a bad ECM without obviously checking the complete wiring harness. Since the new ECM didn't fix the issue, it must be a wiring issue or sensor failure. But to me this sounds like a fault in the wiring harness. The wiring diagram below will help you identify the correct sensor. Let us know what you find.

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