Important: The following steps must be completed before using the symptom tables.
- Perform the
Brake System Vehicle Road Test
before using the Trailer Brake Controls symptom tables in order to duplicate the customer's concern.
- Review the system operation in order to familiarize yourself with the system functions. Refer to the following:
Visual/Physical Inspection
| • | For vehicles displaying a TRAILER NOT CONNECTED message with a trailer connected. |
| • | Inspect the trailer brake connector and circuits for proper connections, perform the following steps: |
| 1. | Verify SSR circuit 47 pin A to the trailer connector pin C for continuity. |
| 2. | Verity SSR circuit 1750 pin B to ground and to the trailer connector pin B for continuity. |
| • | If all circuits test normal the vehicle TBCM system is not at fault, otherwise most associated circuit faults on the vehicle side will set DTC's in the TBCM. |
| • | Insure the trailer is equipped with electric over electric brakes - only trailers equipped with electric brakes will be recognized and function correctly with TBCM. |
| • | If the trailer is equipped with hydraulic brakes this trailer will not be recognized by the TBCM. The vehicle chassis to trailer connector ground or the trailer ground circuits or trailer brake electric magnets are likely at fault. |
| • | The Trailer brake connector should measure less than 2 ohms of resistance between pins A & B of the trailer side connector. Note - a minimum of one fully functioning axle of brakes is required for the TBCM system to function correctly. |
Symptoms Testing
Some customers may experience an intermittent Check Trailer Wiring message in vehicles equipped with ITBC (Integrated Trailer Brake Controller) with no DTC stored. This message may be displayed each time the trailer’s running lamps, turn signal
lamps or brake lamps turn on - especially if the trailer is equipped with a large number of lamp loads.
Check Trailer Wiring Message on the DIC
- This condition is caused by insufficient grounding between the trailer and vehicle.
| • | To correct this condition, perform the following procedure: |
| - | Inspect and clean the ground wire (white wire) connection on the trailer side of the 7-pin connector. |
| - | Make sure that the wires inside the trailer side connector are clean and securely fastened. |
| - | If an electrical junction box exists on the trailer, make sure the wires inside the junction box are clean and securely fastened. |
| • | Once this procedure is complete, check to see if the condition has been corrected: |
| - | Remove the original trailer ground wire (white wire) from the trailer side of the 7-pin trailer connector. |
| - | Install a ring terminal (PN 12103512 or equivalent) to this wire and fasten the ring terminal to the metal or aluminum chassis of the trailer using a M6x1x20 self taping phosphate zinc coated screw (PN 11515925 or equivalent). |
| - | Pre-drill trailer chassis location with a 3/16" hole. Make sure the trailer chassis location is clean of paint or coating material prior to installation. Galvanic corrosion between dissimilar trailer and screw metals may require that this ground
location be periodically cleaned. |
| • | Obtain a sufficient length of minimum 10 gauge (5.0 mm2) white wire and fasten with ring (PN 12103512 or equivalent) terminal to the trailer chassis at the same location as the original ground wire. |
| • | Install and fasten the other end of the new ground wire into the trailer side of the 7-pin trailer connector. |
| • | Install conduit on the original and new trailer ground wires, and secure the conduit to the existing trailer harness. |
- Verify the condition has been corrected.
Intermittent
Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to
Testing for Intermittent Conditions and Poor Connections
.
Symptom List
Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom:
Brake Warning Indicator Malfunction
