Need Help With 2014 Terrain Cuts Out Intermittently

Shawn Technician Eugene, Oregon Posted   Latest   Edited  
Question
Driveability
2014 GMC Terrain SLT 2.4L (K LEA Flex) 6-spd (6T45)
P0651 - Sensor Reference Voltage "B" Circuit/Open
U0401 - Invalid Data Received From ECM/PCM "A"
Cuts Out Under Cruise
Stabilitrac Comes On
Problem Is Intermittant

Driving down road it will intermittently will cut out for a second or so multiple times. It effects all 5v ref. wires grounds and powers at the PCM. Tried direct ground from PCM to battery, no change. It was setting a crankshaft P0336 code, we replaced crank sensor with GM sensor and code is not setting at this time. When MIL and StabiliTrack lamps come on, symptoms seem to go away turn key off then lights go off. Need a little help

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Chris Diagnostician
Lansdale, Pennsylvania
Chris Default
   

Shawn, Could you clarify a few things, if you don't mind? - You say it affects all 5V ref wires, grounds, and powers at the PCM: Have you checked that with a meter hooked up during test drives or is with with scan data; and if so, how does it affect them? - What happens to the 5V ref? - What happens to the grounds? - What happens to the powers? - P0651 refers to Open Circuit on the 5V

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Chris Diagnostician
Lansdale, Pennsylvania
Chris Default
 

Also, if possible, adding the VIN for the vehicle can help us verify if there are TSB (technical service bulletins) or other information relevant to that specific vehicle.

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Shawn Technician
Eugene, Oregon
Shawn Default
 

loosing it at the pcm but the 5v ref. only drops to 4 volts. the ground varies about .5volt to a volt plus or minus the 12 volt ref key on and 12v constant will vary up to 16volts. biggest issue is it will only act up under load at cruise. i have no way to create the issue in stall. im using a pico scope.

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Shawn Technician
Eugene, Oregon
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i tried the 5 volt ref at the brake pedal pos. sensor and crank sensor the drop was exactly the same. then tried another 5v ref still did the same thing. i can get the vin but not till tuesday

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Michael Mobile Technician
Clinton, Utah
Michael Default
 

Hi Shawn, 16 Volts is way too high. Most of the time I see that high of voltage on a late model GM the battery is toast. The voltage should hover between 13.5v and 14.2v from my experience. I would recommend checking the battery with a tester. -Mike

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Chris Diagnostician
Lansdale, Pennsylvania
Chris Default
 

Shawn, I agree with Michael and Paul. Proper voltage is key, and not every manufacturer is always clear about the computer logic responses to over voltage (they don't always know). I would look very closely at the battery and charging system. - Load test battery - Double check all connections (wouldn't hurt to check voltage drop across terminals and up to B+ on alternator.) - Check PCM

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Chris Diagnostician
Lansdale, Pennsylvania
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Shawn, just re read this. I know you said that you won't see the car until Tuesday. See my post above, but also pay attention to that .5V to 1V on the ground you are seeing. If you are truly seeing that much of a voltage drop on a computer ground then it is time to first and foremost load test every ground for the PCM, and wiggle test them at their mounting locations. I apologize for not

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Shawn Technician
Eugene, Oregon
Shawn Default
 

direct ground to wires at pcm, sensor ok loosing 5v ref. the trac light comes on when acting up cruising and the light stays on till you stop the vech, turn the key off . when restarted the trac light is out sometimes the cel is off as well sometimes cel stays on but trac off.,

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Chris Diagnostician
Lansdale, Pennsylvania
Chris Default
   

If I am reading your post correctly, I believe you are saying that you have run auxiliary grounds from the two 451 BK/WH wires at the ECM to the battery or somewhere else? Are there any other codes present besides P0651 and the U0401? Any freeze frame data from the scanner? Is the traction control activating or is it the Service Stabilitrac that displays? I just did a key cycle check in my 13

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Shawn Technician
Eugene, Oregon
Shawn Default
 

stabilitrac lights come on when vech. acts up. driving down the highway never so far in the stall .

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Paul Technical Support Specialist
Lefkosia, Cyprus
Paul Default
 

Hi Shawn, I have never seen a GMC in person in my life and i have no idea for what this vehicle looks like. So i could be very wrong on this. But i was just reading through this, and i noticed one thing. Quote "biggest issue is it will only act up under load at cruise" . May i suggest monitoring the alternator voltage (could possibly be a good idea to have the amperage as well), while the

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Chris Diagnostician
Lansdale, Pennsylvania
Chris Default
 

Quick write up in between jobs here. Apologize for the handwriting. That's the best thought process I can give you with the data we have. Load test those grounds, and check that J103 splice for the grounds. I would get rid of the ground side voltage drop before I chased anything else. The grounds for the all the sensors on Reference B are bussed inside the ECM, and so attacking the problem

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