Service Procedure

1. Check and verify the function of the horn:

a. If the horn is inoperative when the engine IS running, perform normal diagnostics and repair as outlined in Workshop Manual section 413-06. Verify that the condition is corrected and release the vehicle.

b. If the vehicle has a weak horn chirp confirmation when the key fob is used, or an inoperative horn when the engine is NOT running, continue to Step 2.

2. Remove the 20 amp # 7 fuse from the Battery Junction Box.

3. Disconnect the 24-way Truck Central Security Module (TCSM) connector, C256.

4. Leaving enough room on the connector side to splice into the circuits, cut circuit 6, the yellow/light green wire that comes out of cavity 13 of the connector, and circuit 460, the yellow/light blue wire that comes out of cavity 24 of the connector.


5. Using two lengths of **14 GAUGE** wire about 10 inches long, splice into the two circuits that were cut in Step 4. Refer to TSB 01-10-12 for proper splice procedure.

6. Move the power distribution box in the engine compartment aside to gain access to the three 40-pin connectors.

7. From the engine compartment side, unbolt the group of 3 40-way bulkhead connectors that includes C160, and disconnect the C160 connector.

8. Remove the plastic bezel (the plastic cover to be removed after the three connectors are. disconnected). Then squeeze the retaining tabs (two per connector) together to remove the connector from the bulkhead.

9. Disassemble the bulkhead connector from the plastic cover (the plastic handle holds the three connectors as an assembly).

10. Leaving enough room on the connector side to splice into the circuits, cut circuit 6, the yellow/light green wire that comes out of cavity 8 of the connector, and circuit 460, the yellow/light blue wire that comes out of cavity 24 of the connector. Circuits 6 and 460 can be found in the smaller bundle that is taped inside the main bundle that goes to the bulkhead connector.

NOTE
THE EVIM MAY INCORRECTLY IDENTIFY THE YELLOW/LIGHT GREEN WIRE (CIRCUIT 6) AS YELLOW/LIGHT BLUE.

11. Splice the 14 gauge wires that were spliced into the TCSM connector into the matching circuits at the bulkhead connector. Refer to TSB 01-10-12 for proper splice procedure.

12. Secure the new 14 gauge wires into the main bundle that goes to the bulkhead, wrapping them with electrical tape.

13. Install the three connectors back into the plastic cover (plastic handle).

14. Install the connector into the bulkhead.

15. Reconnect the TCSM.

16. Install the plastic bezel and reconnect the three 40-pin connectors.

17. Torque the three connectors to 4.0-5.6 N.m (35-50 Lb-in).

18. Position the power distribution box back into its proper place in the engine compartment.

19. Replace Battery Junction Box fuse # 7.

20. Test horn for proper operation, both with key fob and with engine not running.