Case Study: Infiniti Q50 left turn signal inoperative

July 5, 2023
The customer said her Q50’s left front turn signal stopped working, but the right turn signal worked just fine.

Vehicle: 2014 Infiniti Q50, AWD, V6-3.7L (VQ37VHR), automatic transmission/transaxle

Mileage: 85,009

Problem: The customer’s concern was that her Q50’s left front turn signal stopped working. The right turn signal worked fine. She had her neighbor check the left turn signal bulb and they said it was good.

Case details: The technician performed some initial checks. He verified that the bulb was functioning correctly by swapping the left and right front turn signal bulbs. The good right turn signal bulb did not work on the left side. Checking for power and grounds, the technician found a good ground at the turn signal connector but no battery power. At this point, the technician called ALLDATA Tech-Assis for a little diagnostic guidance.

The Tech-Assist consultant advised back-probing the PIN #117 (WHT/BLK) wire of the body control module (BCM) M16 connector (see image) to check for battery voltage while commanding the turn signal on with a scan tool.

If battery voltage was present, then the problem would be in the wiring or connectors. If there was no battery voltage, then there the problem would be in the BCM itself.

During the wiring and connector inspection, the technician found no battery voltage at PIN #117. The terminal was loose in the connector at the BCM.

Confirmed repair: The technician tightened the terminal in the connector and plugged it back together. He verified the left front turn signal operated as designed. An easy fix!

Reprinted with permission from ALLDATA.

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