Diagnostic Test

VERIFY DTC IS STORED
NOTE: Stored faults may indicate a customer perceived intermittent condition.

NOTE: Ensure the IOD fuse is installed and battery voltage is between 10 and 16 volts before proceeding.
1. With the scan tool, read stored DTCs.
Q: Is this DTC stored?

Yes :
- Go To 2
No :
- Diagnose and repair the DTC. Refer to appropriate DTC.
CHECK THE ENVIRONMENTAL DATA
1. With the scan tool, read the loss of communication environmental data.
Q: Does the loss of communication environmental odometer data match up to any of the previous service procedures listed in the possible causes or are their any stored CAN B or C hardware electrical, battery, ignition voltage, VIN missing/mismatch, FCM configuration DTCs present with matching environmental data?

Yes :
- These DTCs may have been the result of other service procedures performed. Clear DTCs.
No :
- Go To 3
VERIFY INTERMITTENT LOST COMMUNICATION DTC - WIRING CONCERNS
1. Turn the ignition on.
2. With the scan tool, select Special function.
3. Select all DTCs.
Q: Is there more than one ECU with stored DTCs "Logged Against" the module and one or more lost communication DTCs stored in the offending module?

Yes :
- Verify if the vehicle was recently in for this type of service. Otherwise, visually inspect the related wiring harness for chafed, pierced, pinched, and partially broken wires and the wiring harness connectors for broken, bent, pushed out, and corroded terminals. Repair as necessary.
No :
- Go To 4
VERIFY INTERMITTENT LOST COMMUNICATION DTC - OFFENDING MODULE
1. Turn the ignition on.
2. With the scan tool, select Special function.
3. Select all DTCs.
Q: Is there more than one ECU with stored DTCs "Logged Against" the module and NO lost communication DTCs stored in the offending module?

Yes :
- Check for TSB related to this offending module.
No :
- Go To 5
VERIFY INTERMITTENT LOST COMMUNICATION DTC - REPORTING MODULE
1. Turn the ignition on.
2. With the scan tool, select Network Diagnostics.
Q: Is there ONLY ONE ECU with stored DTCs "Logged Against" the module?

Yes :
- Check for TSB related to the module that set this DTC.
No :
- Verify if the vehicle was recently in for this type of service. Otherwise, visually inspect the related wiring harness for chafed, pierced, pinched, and partially broken wires and the wiring harness connectors for broken, bent, pushed out, and corroded terminals. Repair as necessary.