Turn Signal Malfunction Message

Paul Owner/Technician Wisconsin Posted   Latest  
Updated
Electrical
Safety
2017 GMC Sierra 1500 SLT 5.3L (C L83 Flex) 8-spd (8L90) — 3GTU2NEC7HG365925

I have an issue with this showing a fault with the Right rear Directional. This is equipped with factory LED and no modifications. Right side flashes 3 times normally and then flashes fast and message appears. Lights are all working. I swapped left side to right side and problem does not move. I ran a jumper from the BCM Connector X4 pin 4 directly to the back of the connector and no change. I installed my Pico and monitored the ground and the power supply and compared right to left. Voltages where the same and both sides pulled to ground. I also monitored the Voltage and ground from the BCM (X4 pin 4 - Voltage and X6 Pin 22 which is the right tail lamp outage detection signal) and compared that with the connector at the l;amps and they are identical, Measured amperage both sides and both sides are the same at 46ma. I replaced the BCM and programmed it and have the same result. Everything is pointing to a BCM but I find it hard to believe I would have two BCMs that do exactly the same thing. Any ideas?????

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Craig Diagnostician
Illinois
Craig
 

Paul, any trailer wiring harnesses underneath the vehicle? Anything indicating that the vehicle is used for towing?

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Justin Technician
Georgia
Justin
   

Ive had this happen once and it was an issue with the signals in the mirror… Check them. Customer declined repair in my scenario, but Im almost certain it would have fixed my case.

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Mike Owner/Technician
New Jersey
Mike
 

I agree with Justin.

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Paul Owner/Technician
Wisconsin
Paul
 

What was the issue in the mirrors that lead you to this? Curious on what lead you to this for testing purposes. Thanks

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Justin Technician
Georgia
Justin
   

Symptoms were the exact same as yours… This particular truck had a rebuilt title… I don't remember the exact year, but it did have OE LED headlamps and taillamps. It had one incorrect mirror that didn't have the integrated signal LED in it… just a base model mirror. I followed many of the same diagnostic steps as you with the exception of BCM replacement. Unfortunately the customer didn't want…

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Deck Owner/Technician
Iowa
Deck
 

Try replacing the flasher.

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Craig Diagnostician
Illinois
Craig
 

Deck, the flasher is the body control module.

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Glenn Owner/Technician
Texas
Glenn
 

Hello Paul, This sounds like a bulb resistance issue. Aftermarket bulbs can cause this. Another thing to check is associated grounds for poor contact by load testing or simply clean them.

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Juan Technical Support Specialist
Illinois
Juan
 

Going to bomb some questions to try and understand the situation more. What message appears after the flash sequence? What fault code is the BCM setting? Does the fault code set after the flash sequence? Lastly, how do you recreate the flash sequence?

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Todd Diagnostician
Michigan
Todd
 

Paul, I think the outage detection circuit is the issue. I don't know if its normally pulled low or normally pulled high, but compare X6 terminal 22 (right rear outage detection) to X6 terminal 12 (left rear outage detection) with each side activated and they're probably going to be different. So my thought is there is either a short to ground or an open circuit on the right rear outage…

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Paul Owner/Technician
Wisconsin
Paul Update
 

We are currently waiting for the customer to decide if he wants to go further. Thanks for the inputs. If we get this back in, I will post and update and hopefully a resolution!

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