Body Control Systems

U0019 - CAN B BUS

U0019 - CAN B BUS:

WHEN MONITORED
Continuously

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

POSSIBLE CAUSES
- Active U0019 CAN B BUS DTC in front control module
- (D55) CAN B BUS (+) circuit open
- (D54) CAN B BUS (-) circuit open
- A/C heater control

Diagnostic Test

1. VERIFY DTC U0019-CAN B BUS IS ACTIVE

Turn the ignition on.
With the scan tool, read PLGM 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 chaffed, pierced, pinched, and partially broken wires. Also, inspect the related connectors for broken, bent, pushed out, spread, corroded, or contaminated terminals. Perform BODY VERIFICATION TEST - VER 1. Body 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.
Disconnect the Power Liftgate Module C2 connector.
Disconnect the Front Control Module (FCM) C1 harness connector.
Measure the resistance of the (D55) CAN B Bus (+) circuit between the Front Control Module C1 harness connector and the Power Liftgate Module C2 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 BODY VERIFICATION TEST - VER 1. Body 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 Power Liftgate Module C2 connector.

Q: Is the resistance below 2.0 ohms?

YES: Replace the Power Liftgate Module. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Repair the (D54) CAN B Bus (-) circuit for an open. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test