Code B420, Courtesy Light Relay Circuit: Notes

If the courtesy lights did not cycle on and off when BO04 was selected, then this is the relay that set Code B420.

1. Checks to see if the fault is due to an open circuit or short to ground in the circuit. If the courtesy lights are always on, there is a short to ground in the control circuit. If the courtesy lights are never on, there is an open in on of the circuits.
2. Checks to see if the sort to ground is due to the circuits or the BCM.
3. Checks to see if the open circuit is due to the circuit or the BCM.
4. Checks to see if the open circuit is on the power side of the relay.
5. Checks to see if the open circuit is on the ground side of the relay or if the relay is faulty.