Problem: Rear brake lamps and turn signals, inoperative.
Details: The customer stated that the rear brake lamps and turn signals were inoperative. The front turn signals operated as designed. The rear parking lamps, and Center High Mounted Stop Lamp (CHMSL) both operated as designed. All fuses were okay and had power. The tech scanned all modules for codes and found the following codes:
B1643 – Rear Left Turn Control Circuit Low
B1644 – Rear Left Turn Control Circuit High
B1647 – Rear Right Turn Control Circuit Low
B1648 – Rear Right Turn Control Circuit High
B166E – Right Trailer Stop/Turn Over Current
B178C – Left Trailer Stop/Turn Over Current
B210d – Battery Voltage Low
The Tech-Assist Consultant advised to start with the basics. The DTCs indicated high and low circuit voltage issue for the rear turn signals. It’s possible the bulb(s) were defective.
The tech inspected the rear turn signal bulbs and found both blown.
IMPORTANT NOTE: Don’t forget to clear the codes once you’ve identified and repaired the problem. Some modules will shut circuits down to protect itself and other modules. Clearing the codes is how to restore that circuit’s function.
Confirmed Repair: He replaced the blown bulbs and cleared the codes. All exterior lighting operated as designed and no codes returned. Fixed!