Circuit/System Testing

NOTE:

DTC U3003 may set due to an open fuse condition caused by the customers trailer lighting system.

Ignition OFF, disconnect the connector at the K68 Trailer Lamp Control Module.
Verify a test lamp illuminates between ground circuit terminal 13 and B+.
- If the test lamp does not illuminate
  Repair the open/high resistance on circuit 2050 or ground connection.
- Go to next step: If the test lamp illuminates
Test for B+ between B+ circuit terminal 1 and ground:
- If less than B+ and circuit fuse F82UA is open
1. Test circuit 5640 for a short to ground:
  - If a short to ground is found, repair the fault on the circuit.
  - Go to next step: If a short to ground is not found.
2. Replace the open fuse and connect the K68 Trailer Lamp Control Module connector.
3. Ignition on/vehicle in service mode.
4. Verify the fuse does not become open.
  - If the fuse is open
    Replace the K68 Trailer Lamp Control Module
  - Go to next step: If the fuse is not open
5. The customers trailer has an electrical fault causing the fuse to blow.
- If less than B+ and circuit fuse F82UA is OK
1. Test circuit 5640 for an open/high resistance:
  - If an open/high resistance is found, repair the fault on the circuit.
  - Go to next step: If an open/high resistance is not found.
- Go to next step: If B+
Connect the K68 Trailer Lamp Control Module connector, ignition on/vehicle in service mode.
Clear DTCs and verify DTC U3003 does not reset.
- If DTC U3003 resets
  Replace the K68 Trailer Lamp Control Module
- Go to next step: If DTC U3003 does not reset
All OK.