B420 Courtesy Lamp Relay Circuit

BCM Code B420 (Part 2 Of 5):

Courtesy Lamps Relay Circuit:

DESCRIPTION:

If the courtesy lamps did not cycle on and off when B004 was selected, then this is the relay that set code B420.

Numbers below refer to circled numbers on the diagnostic chart.

1. Checks to see if the fault is due to an open circuit or a short to ground in the circuit. If the courtesy lamps are always on, then there is a short to ground in control circuit and if the courtesy lamps never turn on, then there is an open in one of the circuits.

2. Checks to see if the short to ground is due to the circuit 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 side of the relay or the relay.

NOTE ON INTERMITTENTS:

If an intermittent code B420 is being set, manipulate the related wiring in output function and watch for relays to cycle.