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Home >> Jeep >> 2009 >> Commander 2WD V6-3.7L >> Repair and Diagnosis >> A L L Diagnostic Trouble Codes ( DTC ) >> Testing and Inspection >> U Code Charts >> U0020 >> Auto Highbeam Module (AHBM)
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Auto Highbeam Module (AHBM)






U0020-CAN B BUS OFF PERFORMANCE

For a complete wiring diagram, refer to the Wiring Information Electrical Diagrams.

- When Monitored:
Continuously.

- Set Condition:
Whenever the Can B Bus (+) or B Bus (-) circuit is open, shorted to voltage or shorted to ground, this code will set.





1. TEST FOR INTERMITTENT CONDITION
1. Turn the ignition on.
2. Using the scan tool, erase all DTCs.
3. Cycle the ignition from on to off three times.
4. Turn the ignition on.
5. Using the scan tool, read DTCs.

Does the scan tool display active: U0020-CAN B BUS OFF PERFORMANCE?

Yes

- Go To 2

No

- The condition that caused this symptom is currently not present. 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. Repair as necessary.
- Perform the BODY VERIFICATION TEST. Body Verification Test.

2. CHECK FRONT CONTROL MODULE DTCs
1. Using the scan tool, read Front Control Module DTCs

Does the scan tool display any CAN B BUS DTCs - ACTIVE?

Yes

- Perform the U0020-CAN B Bus Off Performance diagnostic procedure. U0020

No

- Go To 3

3. CAN B BUS (+) CIRCUIT OPEN
1. Turn the ignition off.
2. Disconnect the AHBM harness connector.
3. Disconnect the Front Control Module C1 harness connector.
4. Measure the resistance of the (D55) Can B Bus (+) circuit between the Front Control Module C1 harness connector and the AHBM harness connector.

Does the Ohm meter read open circuit?

Yes

- Repair the Can B Bus (+) circuit for an open.
- Perform the BODY VERIFICATION TEST. Body Verification Test.

No

- Go To 4

4. CAN B BUS (-) CIRCUIT OPEN
1. Measure the resistance of the (D54) Can B Bus (-) circuit between the Front Control Module C1 harness connector and the AHBM harness connector.

Does the Ohm meter read open circuit?

Yes

- Repair the Can B Bus (-) circuit for an open.
- Perform the BODY VERIFICATION TEST. Body Verification Test.

No

- Replace the AHBM.
- Perform the BODY VERIFICATION TEST. Body Verification Test.

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