2007 Liberty KJ Factory Service Manual 8 - ELECTRICAL

*CAN C BUS COMMUNICATION FAILURE





For a complete wiring diagram Refer to Section 8W.



Possible Causes
  
(D65) CAN C BUS (+) CIRCUIT SHORTED TO VOLTAGE
  
(D64) CAN C BUS (-) CIRCUIT SHORTED TO VOLTAGE
  
(D65) CAN C BUS (+) CIRCUIT SHORTED TO GROUND
  
(D64) CAN C BUS (-) CIRCUIT SHORTED TO GROUND
  
(D65) CAN C BUS (+) CIRCUIT SHORTED TO (D64) CAN C BUS (-) CIRCUIT
  
ANTILOCK BRAKE MODULE
  
POWERTRAIN CONTROL MODULE (PCM or ECM)
  
STEERING ANGLE SENSOR
  
BODY CONTROL MODULE
  



Diagnostic Test

1. VERIFY CAN C BUS COMMUNICATION

Turn the ignition on.

NOTE: Ensure the IOD fuse is installed and battery voltage is between 10.0 and 16.0 volts.


With the scan tool select ECU View.

NOTE: A red X will be next to the module that is not communicating or not installed on the vehicle, indicating that the module is not active on the Bus network. A green check indicates that the module is active on the Bus network.



Does the scan tool communicate with any module on the CAN C Bus circuit?

Yes


No

2. CHECK THE D65 CAN C (+) AND (D64) CAN C (-) CIRCUITS FOR A SHORT TO VOLTAGE



Turn the ignition on.
Measure the voltage of the (D65) CAN C Bus (+) circuit and the (D64) CAN C Bus (-) circuit at the DLC.

Is the voltage steadily above 4.0 volts?

Yes


No

3. (D65) CAN C BUS (+) CIRCUIT OR (D64) CAN C BUS (-) CIRCUIT SHORTED TO VOLTAGE



Turn the ignition off.
Disconnect the scan tool from the DLC.

NOTE: Perform the following steps for each module on the CAN C Bus Circuit.


Measure the voltage between the (D65) CAN C Bus (+) circuit and the (D64) CAN C Bus (-) circuit and ground at the DLC.
Disconnect a module, turn the ignition on and check if the module that was disconnected was causing the short to voltage internally.
While monitoring the voltmeter, disconnect each module on the CAN C Bus Circuit one at a time.

Is there any voltage present with all modules disconnected?

Yes


No

4. CHECK THE (D65) CAN C BUS (+) CIRCUIT AND THE (D64) CAN C BUS (-) CIRCUIT FOR A SHORT TO GROUND



Turn the ignition off.
Measure the resistance between the (D65) CAN C Bus (+) circuit and ground and the (D64) CAN C Bus (-) circuit and ground at the DLC.

Is the resistance below 5.0 ohms on either circuit?

Yes


No

5. (D65) CAN C BUS (+) CIRCUIT OR (D64) CAN C (-) CIRCUIT SHORTED TO GROUND



Turn the ignition off.

NOTE: Perform the following steps for each module on the CAN C Bus Circuit.


Measure the resistance between the (D65) CAN C Bus (+) circuit and the (D64) CAN C Bus (-) circuit and ground at the DLC.
Disconnect a module, check if the module that was disconnected was causing the short to ground internally.
While monitoring the ohmmeter, disconnect each module on the CAN C Bus Circuit one at a time.

Is the resistance below 5.0 ohms with all modules disconnected?

Yes


No

6. (D65) CAN C BUS (+) CIRCUIT SHORTED TO (D64) CAN C BUS (-) CIRCUIT



NOTE: Perform the following steps for each module on the CAN C Bus Circuit.


Measure the resistance between the (D65) CAN C Bus (+) circuit and the (D64) CAN C Bus (-) circuit at the DLC.
Disconnect a module, check if the module that was disconnected was causing the short internally.
While monitoring the ohmmeter, disconnect each module on the CAN C Bus Circuit one at a time.

Is the resistance below 5.0 ohms with all modules disconnected?

Yes


No