2007 Liberty KJ Factory Service Manual 8 - ELECTRICAL

*PCI BUS COMMUNICATION FAILURE





For a complete wiring diagram Refer to Section 8W.



Possible Causes
  
(D25) PCI BUS CIRCUIT OPEN AT DATA LINK CONNECTOR (DLC)
  
(D25) PCI BUS CIRCUIT SHORTED TO GROUND
  
(D25) PCI BUS CIRCUIT SHORTED TO VOLTAGE
  
ANY PCI BUS MODULE INTERNALLY SHORTED TO GROUND
  
ANY PCI BUS MODULE INTERNALLY SHORTED TO VOLTAGE
  



Diagnostic Test

1. PCI BUS COMMUNICATION AND TEST FOR INTERMITTENT CONDITION

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 PCI Bus network?

Yes


No

2. (D25) PCI BUS CIRCUIT OPEN AT THE DLC


NOTE: If the PCI Bus circuit is open between the BCM and the DLC the scan tool will be unable to identify the vehicle. Perform the test below to determine if the open condition exists causing the scan tool error.


Turn the ignition off.
Disconnect the negative battery cable.
Disconnect the scan tool from the DLC.
Disconnect the BCM C1 harness connector.
Measure the resistance of the (D25) PCI Bus circuit between the DLC and the BCM harness connector.

Is the resistance below 5.0 ohms?

Yes


No

3. CHECK THE (D25) PCI BUS CIRCUIT FOR A SHORT TO VOLTAGE



NOTE: Reconnect the BCM harness connector and the negative battery cable.


Turn the ignition on.
Measure the voltage of the (D25) PCI Bus circuit at the DLC.

Is the voltage steadily above 7.0 volts?

Yes


No

4. (D25) PCI BUS CIRCUIT SHORTED TO VOLTAGE


NOTE: If the PCI Bus circuit is shorted to voltage the scan tool will be unable to identify the vehicle. Perform the test below, make the repairs as indicated. Re-attempt communication with the scan tool.


Turn the ignition off.
Using a voltmeter, connect one end to the (D25) PCI Bus circuit at the DLC and the other end to ground.

NOTE: For each module on the PCI Bus perform the following steps.


Turn the ignition off, wait one minute before disconnecting a module, turn the ignition on and check if the module disconnected was causing the short to voltage internally.
While monitoring the voltmeter, disconnect each module the vehicle is equipped with one at a time.

Is the voltage steadily above 7.0 volts with all the modules disconnected?

Yes


No

5. (D25) PCI BUS CIRCUIT SHORTED TO GROUND


NOTE: If the PCI Bus circuit is shorted to ground the scan tool will be unable to identify the vehicle. Perform the test below, make the repairs as indicated. When the repair is complete unplug the IOD fuse, wait 30 seconds, and plug the fuse back in. This will re-initialize the BCM. Re-attempt communication with the scan tool.


Turn the ignition off.
Using a ohmmeter, connect one end to the (D25) PCI Bus circuit at the DLC and the other end to ground.
While monitoring the ohmmeter, disconnect each module the vehicle is equipped with one at a time.

NOTE: Total bus resistance to ground thru all of the modules is typically between 350 to 1000 ohms. The more modules on the PCI Bus, the lower the total resistance will be.



Is the resistance below 150.0 ohms with all the modules disconnected?

Yes


No