Malibu 2.4 Start / Stall

Bill Owner/Technician Jackson, Michigan Posted   Latest  
2010 Chevrolet Malibu LT 2.4L (B) 6-spd (6T40)—1G1ZC5EB3A4165923

Yesterday i had a Malibu towed in for a start/ stall condition. Vehicle starts every time runs for 1-2 sec and stalls. No codes present in ECU. I checked fuel pressure, relative compression, and scoped the cam signals... Everything seemed OK.

When doing some Information research on another site -i find countless tips about unplugging the intake cam sensor and starting the vehicle. I tried it and the vehicle started and ran normally?- I found once the engine is running you can plug in the cam sensor and it keeps running just fine... If you clear codes the vehicle stalls....BUT WHY??? So i took another look at cam signal and reference voltage - both still looking normal/good. 

I read other tech tips that say to disconnect the battery and short cables for 10 minutes to fix this issue. I tried that and now the vehicle starts and runs normally every time with cam sensor plugged in. Cam Position Variance never exceeds 4 degree when phasing. 

Can somebody explain what is going on? What caused the initial condition of Start/Stall? I don't want to ship it and have it towed back

Albert Owner/Technician
Towanda, Pennsylvania
Albert Default

Good question, I never had this happen and also would like to know why that way I can be prepared

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Robert Business Development Manager
Brookfield, WI, Wisconsin
Robert Default

PCM software got corrupted. I would update PCM to the latest flash. If that doesn't cure problem long term, then hardware problem in PCM.

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Trevor Owner/Technician
Church Crookham, United Kingdom
Trevor Default

Could it be a immobiliser fault or poss crank sensor fault 🤔🤔🤔🤔

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Stuart Mobile Technician
Blue Island, Illinois
Stuart Default

I had a similar situation with the same vehicle and engine after replacing the motor.I just turned the key without starting until the security light started flashing,about 10 minutes and the car ran great​.​Has to be the security needing resetting.

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Philip Educator
Hemet, California
Philip Default

Do you set a cam sensor circuit code when the CMP is disconnected? At least a pending code? If not, it certainly sounds like a hardware or software failure. I would at least update the software and warn the customer that if it happens again, the PCM will need replacing.

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Bill Owner/Technician
Jackson, Michigan
Bill Default

Yes - cam codes do set with them unplugged. Vehicle arrived with NO faults

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Randall Technician
Kunkletown, Pennsylvania
Randall Default

Bill, I had a Pontiac G-6 towed in, same as you describe. Check G109 left radiator support. Should test it. Definitely take apart and clean. (Ground for PCM run relay) hope this helps, Randy

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J. Owner/Technician
Clute, Texas
J. Default

I would try a battery reset ,cam crank correlation relearn and check for TSB’s, What about a weak sensor

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Robert Technician
Trevose, Pennsylvania
Robert Default

I have seen a number of problems on GM vehicles that a battery disconnect and holding the cables together fixed. Where I work has a fleet of Chevy pickups and the instrument clusters would go out and this would fix it. I have found this usually happens after a jump start. I think GM calls this logic lock. If it had a battery or charging system problem just before this problem I wouldn’t worry…

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Bill Owner/Technician
Jackson, Michigan
Bill Update

Possibly logic lock was the culprit here.... But why or how we will never know perhaps. We kept the vehicle for 3 days started and drove it multiple times over that period with no further issues. Looking at cam and crank pattern we seen nothing unusual either. ECU software was at the latest calibration offered. I will follow up if it returns. Thank you for your thoughts and time

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Andrew Technician
Milwaukee, Wisconsin
Andrew Default

I’ve seen this about 20 times. The original problem is the base timing. This is usually a stretched/worn timing chain or an actuator that’s hanging up. The ECM detects the the engine out of time so it doesn’t start to protect it. No idea why it doesnt set codes. Unplugging the cam sensor bypasses this and allows it to start because it doesn’t have a reading to compare it to. 2 times I’ve seen it…

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