Restraints

U0020-CAN B BUS OFF PERFORMANCE

U0020 - Can B Bus Off Performance:

WHEN MONITORED
Continuously

SET CONDITION
Whenever the CAN B Bus (+) or CAN B Bus (-) circuit is open, shorted to voltage, or shorted to ground.

POSSIBLE CAUSES
- Active U0020 CAN B BUS DTC in occupant classification module
- (D55) CAN B BUS (+) circuit open
- (D54) CAN B BUS (-) circuit open
- Occupant classification module (OCM)

Diagnostic Test

1. VERIFY DTC U0020-CAN B BUS IS ACTIVE

Turn the ignition on.
With the scan tool, read Occupant Classification Module (OCM) DTCs.

Q: Does the scan tool display active: U0019-CAN B BUS?

YES: Go To 2
NO: If the DTC is stored, check for an intermittent condition by inspecting the related wiring harness for chafed, pierced, pinched, and partially broken wires. Also, inspect the related connectors for broken, bent, pushed out, spread, corroded, or contaminated terminals. Perform the AIRBAG SYSTEM VERIFICATION TEST - VER 1. Airbag System Verification Test

2. CHECK FOR ACTIVE CAN B BUS RELATED DTCS IN THE FRONT CONTROL MODULE (FCM)

With the scan tool, read Front Control Module (FCM) DTCs

Q: Does the scan tool display any active CAN B BUS related DTCs?

YES: Diagnose and repair the DTC(s).
NO: Go To 3




3. CHECK (D55) CAN B BUS (+) CIRCUIT FOR AN OPEN

Turn the ignition off.
Disconnect the negative battery cable.

WARNING: TO AVOID PERSONAL INJURY OR DEATH, TURN THE IGNITION OFF, DISCONNECT THE BATTERY AND WAIT TWO MINUTES BEFORE PROCEEDING.

Disconnect the OCM connectors.
Disconnect the Front Control Module (FCM) C1 connector.
Measure the resistance of the (D55) CAN B Bus (+) circuit between the Front Control Module C1 connector and the OCM C1 connector.

Q: Is the resistance below 2.0 ohms?

YES: Go To 4
NO: Repair the (D55) CAN B Bus (+) circuit for an open. Perform the OCCUPANT CLASSIFICATION MODULE SYSTEM VERIFICATION TEST. Occupant Classification Module (OCM) System Verification Test




4. CHECK (D54) CAN B BUS (-) CIRCUIT FOR AN OPEN

Measure the resistance of the (D54) CAN B Bus (-) circuit between the Front Control Module C1 connector and the OCM C1 connector.

Q: Is the resistance below 2.0 ohms?

YES: Replace the OCM. Perform the OCCUPANT CLASSIFICATION MODULE SYSTEM VERIFICATION TEST. Occupant Classification Module (OCM) System Verification Test
NO: Repair the (D54) CAN B Bus (-) circuit for an open. Perform the OCCUPANT CLASSIFICATION MODULE SYSTEM VERIFICATION TEST. Occupant Classification Module (OCM) System Verification Test