Start by checking the "Possible Causes" listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector's pins.
The cost to diagnose the B127B GMC code is 1.0 hour of labor. The auto repair's diagnosis time and labor rates vary by location, vehicle's make and model, and even your engine type. Most auto repair shops charge between $75 and $150 per hour.
When the vehicle is placed in reverse with the engine running, a voltage signal is sent to the rearview camera to turn on and send a video signal to the Human Machine Interface Control Module. If the Human Machine Interface Control Module does not see a signal from the camera it will set B127B 2B and display Service Rear Vision System.
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