Tech Tip: Engine stalls with daytime running lights on

May 7, 2024
A customer brought a 2015 Jeep Grand Cherokee in due to the engine stalling when the DRLs were turned on.

A customer brought his 2015 Jeep Grand Cherokee into the shop because the engine stalled whenever the daytime running lights (DRLs) were on. He also mentioned that if he pulls the handbrake (which disables DRLs), the engine stays running. 

Case details

The technician connected a scan tool and pulled the following diagnostic trouble codes (DTCs):

  • U0100 - Lost communication with ECM/PCM
  • U0102 - Lost communication with transfer control module / AWS
  • B2335 - Horn control - Circuit short to battery or open

Given the diverse types of DTCs, the technician decided to call ALLDATA for help. The ALLDATA Tech-Assist consultant advised that when faced with a list of unrelated DTCs, check for common ground issues. In this case, he recommended checking ground G909A at the right rear of the engine compartment. All DTC components shared that ground point. 

The technician inspected ground G909A as suggested and found the ground connection was indeed loose and corroded.

Confirmed repair

The technician cleaned the terminals and tightened the ground point. He cleared the DTCs, and test-drove the vehicle. The engine no longer stalled with the DRLs on.

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