Diagnostic Test

WARNING: This page is about a different car, the 2005 Jeep Grand Cherokee. However, it is still accessible from the selected car via links, so may be relevant.

TEST FOR INTERMITTENT CONDITION
Turn the ignition on.

With the scan tool, record and erase DTC's

Cycle the ignition from on to off 3 times.

Turn the ignition on.

With the scan tool, read DTC's.

Does the scan tool display U1107 ECU IN SINGLE-WIRE MODE?
- Yes: Go To 2
- No: The conditions that caused this code to set are not present at this time. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors.
CHECK FRONT CONTROL MODULE DTC's
With the scan tool, read Front Control Module DTC's

Does the scan tool display any CAN B BUS DTC's - ACTIVE?
- Yes: Refer to the symptom list for problems related to Communication in ELECTRONIC CONTROL MODULES - ELECTRICAL DIAGNOSTICS .
- No: Go to 3
CAN B BUS (+) CIRCUIT OPEN
Turn the ignition off.

Disconnect the Heated Seat Module connector.

Disconnect the Front Control Module C1 connector.

Measure the resistance of the (D55) Can B Bus (+) circuit between the Front Control Module C1 connector and the Heated Seat Module connector.

Is the resistance below 2.0 ohms?
- Yes: Go To 4
- No: Repair the Can B Bus (+) circuit for an open.
  Perform BODY VERIFICATION TEST - VER 1 .
Fig 1: Checking Can B Bus (+) Circuit Open
Courtesy of DAIMLERCHRYSLER CORPORATION
CAN B BUS (-) CIRCUIT OPEN
Measure the resistance of the (D54) Can B Bus (-) circuit between the Front Control Module C1 connector and the Heated Seat Module connector.

Is the resistance below 2.0 ohms?
- Yes: Replace the Heated Seat Module.
  Perform BODY VERIFICATION TEST - VER 1 .
- No: Repair the Can B Bus (-) circuit for an open.
  Perform BODY VERIFICATION TEST - VER 1 .
Fig 2: Checking Can B Bus (-) Circuit Open
Courtesy of DAIMLERCHRYSLER CORPORATION