Code B420 - High/Low Beam Relays Circuit: Notes

If high/low beam did not cycle on and off when BO06 was selected, then high/low beam relay set code B420.

1. Checks if fault is caused by an open circuit or short to ground. If high beams are always on, then there is a short to ground. If high beams never turn on, then there is an open in one of the circuits.
2. Checks if short to ground is due to circuit or BCM.
3. Checks if open circuit is due to circuit or BCM.
4. Checks if open circuit is on the power or ground side of relay.