Here’s another fix where the cause of an electrical gremlin was not found by traditional means but instead by looking all around the vehicle. Follow this Real Fix to see how a Ford F150 with malfunctioning radio and climate control system was diagnosed and the component that caused the problem was found.
Vehicle
2016 Ford F-150 Lariat 3.5L
Title
Radio and HVAC inoperative, replaced taillight.
Complaint
The technician reports that the radio and heating, ventilation and air conditioning (HVAC) will operate correctly when in the “key on, engine off” (KOEO) state, but stops working in the “key on, engine running” (KOER) state. When this occurs, the technician reports that the radio touch screen will light up but will not respond, and no communication can be established between the scanner and the radio module.
Cause
The technician reviewed the system wiring diagrams and visually checked the wiring for faults, but found none. Used a multi-meter to verify that power and ground were present at the radio and both were present. Pulled the floor carpet up to inspect the body wiring harness and look for any signs of water intrusion. No issues were found. Noticed there was standing water in one of the taillight assemblies, originating from a cracked tail light lens. Discovered that water had infiltrated the tail light module within the tail light assembly. This caused corrosion and moisture issue, which affected the communication with other modules on the communication bus.
Correction
Replaced the tail light assembly and verified that the vehicle’s radio and air conditioning system worked properly after the repair.