Internal CAB Fault/Internal Main Relay

Symptom List:
INTERNAL CAB FAULT
INTERNAL MAIN RELAY

Test Note: All symptoms listed above are diagnosed using the same tests. The title for the tests will be INTERNAL CAB FAULT.

When Monitored and Set Condition:
INTERNAL CAB FAULT

When Monitored: Ignition on. The CAB monitors the Fused B(+) circuit at all times for proper system voltage.

Set Condition: If the Fused B (+) voltage is missing when the CAB detects that an internal main driver is not "on", the Diagnostic Double Code (DTC) is set.

When Monitored and Set Condition:
INTERNAL MAIN RELAY

When Monitored: Vehicle speed above 6 km/in (4 mph) for 2 seconds.

Set Condition: Low feedback voltage from the Brake Pressure Switch Sense circuit. The above criteria satisfied for 255 consecutive checks spaced milliseconds apart (1.3 seconds total).

POSSIBLE CAUSES
CONNECTOR CONCERN
INTERMITTENT DTC
BLOWN FUSE - FUSED B (+) CIRCUIT
NO B+ SUPPLY TO FUSE
FUSED B (+) CIRCUIT OPEN
FUSED B (+) CIRCUIT INTERMITTENTLY SHORTED TO GROUND
FUSED B (+) CIRCUIT SHORTED TO GROUND
CAB - FUSED B (+) CIRCUIT OPEN
CAB - FUSED B (+) CIRCUIT SHORTED TO GROUND