Gauge Always Indicates Full (Commercial)
- Disconnect fuel level sensor. Turn ignition on. Connect fused jumper wire between harness side of fuel level sensor connector terminal Purple wire and ground. If fuel gauge remains full, go to next step. If fuel gauge moves toward empty, replace fuel level sensor.
- Remove jumper wire. Backprobe between instrument cluster terminal No. 30 (Purple wire) and ground. If fuel gauge moves toward empty, repair open circuit in Purple wire. If fuel gauge remains full, replace instrument cluster.