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Diagnostic Test

WARNING: This page is about a different car, the 2007 Chrysler PT Cruiser. However, it is still accessible from the selected car via links, so may be relevant.
  1. 1) VERIFY DTC U0020-CAN B BUS IS ACTIVE 

    Turn the ignition on.

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

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

    Yes 

    1. Go to  2).

    No 

    1. 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.
    2. Perform *AIRBAG SYSTEM VERIFICATION TEST - VER 1 .
  2. 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

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

    Yes 

    1. Diagnose and repair the DTC(s). Refer to DIAGNOSIS AND TESTING . .

    No 

    1. Go to  3).
  3. 3) CHECK (D55) CAN B BUS (+) CIRCUIT FOR AN OPEN 
    Fig 1: Checking CAN B BUS (+) Circuit For An Open
    GC0027714Courtesy of CHRYSLER LLC

    Turn the ignition off.

    Disconnect the negative battery cable.

    WARNING: To avoid serious or fatal injury, 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.

    Is the resistance below 2.0 ohms? 

    Yes 

    1. Go to  4).

    No 

    1. Repair the (D55) CAN B Bus (+) circuit for an open.
    2. Perform *OCM SYSTEM VERIFICATION TEST .
  4. 4) CHECK (D54) CAN B BUS (-) CIRCUIT FOR AN OPEN 
    Fig 2: Checking CAN B BUS (-) Circuit For An Open
    GC0027715Courtesy of CHRYSLER LLC

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

    Is the resistance below 2.0 ohms? 

    Yes 

    1. Replace the OCM in accordance with the Service Information.
    2. Perform *OCM SYSTEM VERIFICATION TEST .

    No 

    1. Repair the (D54) CAN B Bus (-) circuit for an open.
    2. Perform *OCM SYSTEM VERIFICATION TEST .
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