Code B420 (D), Dis Clock Circuit: Notes
If DIS is not functioning correctly, then this is the system that set code B420.
NOTE:
Test numbers refer to numbers on diagnostic chart.
Test Number 1) Checks to see if fault is due to an open circuit or a short to ground in circuit. If test light is always on, then there is a short to voltage in control circuit. If test light never turns on, then there is an open or short to ground in circuit.