| Diagnosis and Testing Refer to Wiring Diagrams Section 417-01, for schematic and connector information. Special Tool(s) | | Terminal Probe Kit 29-011A | Inspection and Checking NOTE:The generic electronic module (GEM) forms part of the central junction box (CJB). NOTE:Before reading out the vehicle-specific data, remake all the electrical connections which were separated in the vehicle, so that communication between the module and WDS is ensured. - Verify the customer concern.
- Visually check the following electrical causes for the concern:
Visual Inspection | Electrical | - Fuse(s)
- Bulb(s)
- Connectors
- Trailer socket
- Trailer lamps
- Wiring loom
| - Resolve any obvious causes or concerns found during the visual inspection before carrying out any further tests.
- If the cause of the concern cannot be found by visual inspection, continue with the symptom chart.
Symptom Chart Symptom Chart | Symptom | Possible Sources | Action | | Trailer lamps inoperative | * Fuse(s) * Circuit(s) in vehicle * Circuit(s) in trailer * Trailer socket * Trailer control unit * Trailer relay, reversing lamp * Rear fog lamp cut-off relay * Central Junction Box (CJB) | * | | One individual trailer lamp inoperative | * Circuit(s) in vehicle * Circuit(s) in trailer * Trailer control unit | * | | Trailer lamps illuminate continuously | * Circuit(s) in vehicle * Circuit(s) in trailer * Trailer socket * Trailer control unit * Trailer relay, reversing lamp | * | System Checks NOTE:Use a digital multimeter for all electrical measurements. | PINPOINT TEST A : TRAILER LAMPS INOPERATIVE | | TEST CONDITIONS | DETAILS/RESULTS/ACTIONS | | A1: DETERMINE WHICH LAMPS ON THE TRAILER ARE INOPERATIVE | | | 1 Ignition switch in position II. | | | 2 Switch on the SIDE LIGHTS, STOP LAMPS, REAR FOG LAMPS and LEFT and RIGHT-HAND TURN SIGNAL LAMPS in turn. ENGAGE reverse gear. | | | 3 Check the trailer lamps. | | | Are all lamps on the trailer inoperative? Yes No - Stop lamps, reversing lamps and turn signal lamps inoperative: GO to A3. - Only stop lamps inoperative: GO to A7. - Only reversing lamp(s) inoperative: GO to A10. - Only rear fog lamp(s) inoperative: GO to A15. - Only turn signal lamps inoperative (both sides): RENEW the trailer control unit. CHECK the operation of the system. | | A2: CHECK THE GROUND CONNECTION OF THE TRAILER SOCKET | | | 1 Ignition switch in position 0. | | | 2 Measure the resistance between: - 7-pin trailer socket: connector C2003, pin 3, circuit (BN/WH), and ground.
- 13-pin trailer socket: connector C2009, pin 3, circuit (BN/WH) and ground and between pin 13, circuit (BN) and ground.
| | | Is the resistance less than 2 Ohm? Yes Continue fault finding on the trailer. CHECK the operation of the system. No LOCATE and RECTIFY the break in the circuit between the trailer socket and ground G77 using the Wiring Diagrams. CHECK the operation of the system. | | A3: CHECK FUSE F59 (CJB) | | | 1 CHECK fuse F59 (20 A) (CJB). | | | Is the fuse OK? Yes No RENEW fuse F59 (20 A). CHECK the operation of the system. If the fuse blows again, LOCATE and RECTIFY the short circuit to ground using the Wiring Diagrams. | | A4: CHECK THE VOLTAGE AT FUSE F59 (CJB) | | | 1 Connect fuse F59 (20 A) (CJB). | | | 2 Ignition switch in position II. | | | 3 Measure the voltage between fuse F59 (20 A) and ground. | | | Does the meter display battery voltage? Yes - Vehicles with 13-pin trailer socket: Stop lamps, reversing lamps and turn signal lamps inoperative: LOCATE and REPAIR break in circuit 30-LF29 (RD), between fuse F59 and intermediate connector C305, pin 1, using the wiring diagrams. CHECK the operation of the system. - Stop lamps and turn signal lamps inoperative: GO to A5. No INSTALL a new central junction box (CJB). CHECK the operation of the system. | | A5: TEST THE VOLTAGE SUPPLY OF THE TRAILER CONTROL UNIT | | | 1 Ignition switch in position 0. | | | 2 Disconnect trailer control unit from connector C2002. | | | 3 Ignition switch in position II. | | | 4 Measure the voltage between the trailer control unit, connector C2002, pin 1, circuit (RD), wiring harness side and ground. | | | Does the meter display battery voltage? Yes No - Vehicles with 7-pin trailer socket: LOCATE and RECTIFY the break in the circuit between fuse F59 (CJB) and the trailer control unit using the Wiring Diagrams. CHECK the operation of the system. - Vehicles with 13-pin trailer socket: LOCATE and RECTIFY the break in the circuit (RD) between intermediate connector C305, pin 1 and the trailer control unit using the Wiring Diagrams. CHECK the operation of the system. | | A6: CHECK THE GROUND CONNECTION OF THE TRAILER CONTROL UNIT | | | 1 Ignition switch in position 0. | | | 2 Measure the resistance between the trailer control unit, connector C2002, pin 3, circuit (BN), wiring harness side and ground. | | | Is the resistance less than 2 Ohm? Yes Continue fault finding on the trailer. If the electrical system on the trailer is OK, RENEW the trailer control unit. CHECK the operation of the system. No LOCATE and RECTIFY the break in the circuit between the trailer control unit and ground G77 using the Wiring Diagrams. CHECK the operation of the system. | | A7: CHECK THE VOLTAGE AT THE TRAILER SOCKET WITH THE STOP LAMPS SWITCHED ON | | | 1 Ignition switch in position 0. | | | 2 Disconnect stop lamp switch from connector C444. | | | 3 Connect a fused jumper wire (15 A) to the stop lamp switch, connector C444, between pin 2, circuit 15-LG23 (GN/WH) and pin 1, circuit 15S-LG23 (GN/WH), wiring harness side. | | | 4 Ignition switch in position II. | | | 5 Measure the voltage between the trailer socket: - 7-pin socket: connector C2003, pin 6, circuit (VT), and ground.
- 13-pin socket: connector C2009, pin 6, circuit (VT), and ground.
| | | Does the meter display battery voltage? Yes Continue fault finding on the trailer. No | | A8: CHECK THE VOLTAGE AT THE TRAILER CONTROL UNIT WITH THE STOP LAMPS SWITCHED ON | NOTE:The jumper lead used in the previous step is still connected. | | | 1 Ignition switch in position 0. | | | 2 Disconnect trailer control unit from connector C2002. | | | 3 Ignition switch in position II. | | | 4 Measure the voltage between the trailer control unit, connector C2002, pin 4, circuit (BK/RD) and ground. | | | Does the meter display battery voltage? Yes No LOCATE and RECTIFY the break in the circuit between intermediate connector C2004, pin 5 and the trailer control unit using the Wiring Diagrams. CHECK the operation of the system. | | A9: CHECK THE TRAILER CONTROL UNIT | NOTE:The jumper lead used in the previous step is still connected. | | | 1 Ignition switch in position 0. | | | 2 Using a fused test cable (15 A) at the trailer control unit, connector C2002, bridge between pin 4, circuit (BK/RD) and pin 2, circuit (VT), wiring harness side. | | | 3 Ignition switch in position II. | | | 4 Measure the voltage between the trailer socket: - 7-pin socket: connector C2003, pin 6, circuit (VT), and ground.
- 13-pin socket: connector C2009, pin 6, circuit (VT), and ground.
| | | Does the meter display battery voltage? Yes RENEW the trailer control unit. CHECK the operation of the system. No LOCATE and RECTIFY the break in the circuit (VT) between the trailer control unit and the trailer socket using the Wiring Diagrams. CHECK the operation of the system. | | A10: CHECK THE VOLTAGE AT THE TRAILER SOCKET WITH THE REVERSING LAMPS SWITCHED ON | | | 1 Ignition switch in position II. | | | 2 ENGAGE reverse gear. | | | 3 Measure the voltage between the trailer socket C2009, pin 8, circuit (VT/OG) and ground. | | | Does the meter display battery voltage? Yes Continue fault finding on the trailer. No | | A11: CHECK THE VOLTAGE AT THE TRAILER RELAY, REVERSING LAMP, WITH REVERSING LAMPS SWITCHED ON | | | 1 Ignition switch in position 0. | | | 2 Disconnect trailer relay, reversing lamps, from socket C2012. | | | 3 Ignition switch in position II. | | | 4 ENGAGE reverse gear. | | | 5 Measure the voltage between the trailer relay, reversing lamp, connector C2012, circuit (BK), wiring harness side and ground. | | | Does the meter display battery voltage? Yes No LOCATE and RECTIFY the break in the circuit (BK) between intermediate connector C2004, pin 7 and the trailer relay, reversing lamp, using the Wiring Diagrams. CHECK the operation of the system. | | A12: CHECK THE VOLTAGE SUPPLY TO THE TRAILER RELAY, REVERSING LAMP | | | 1 Measure the voltage between the trailer relay, reversing lamp, connector C2012, circuit (RD), wiring harness side and ground. | | | Does the meter display battery voltage? Yes No LOCATE and RECTIFY the break in the circuit (RD) between intermediate connector C305, pin 1 and the trailer relay, reversing lamp, using the Wiring Diagrams. CHECK the operation of the system. | | A13: CHECK THE GROUND CONNECTION OF THE TRAILER RELAY, REVERSING LAMP | | | 1 Ignition switch in position 0. | | | 2 Measure the resistance between the trailer relay, reversing lamp, socket C2012, circuit (BN), wiring harness side and ground. | | | Is the resistance less than 2 Ohm? Yes No LOCATE and RECTIFY the break in the circuit between the trailer relay, reversing lamp, and ground G77 using the Wiring Diagrams. CHECK the operation of the system. | | A14: CHECK THE TRAILER RELAY, REVERSING LAMP | | | 1 Use a fused test cable (20 A) to bridge the trailer relay, reversing lamp, socket C2012, circuit (BK) and circuit (VT/OG), wiring harness side. | | | 2 Ignition switch in position II. | | | 3 ENGAGE reverse gear. | | | 4 Measure the voltage between the trailer socket C2009, pin 8, circuit (VT/OG) and ground. | | | Does the meter display battery voltage? Yes RENEW the trailer relay, reversing lamp. CHECK the operation of the system. No LOCATE and RECTIFY the break in the circuit between the trailer relay, reversing lamp, and the trailer socket using the Wiring Diagrams. CHECK the operation of the system. | | A15: CHECK THE VOLTAGE AT THE TRAILER SOCKET WITH THE REAR FOG LAMPS SWITCHED ON | | | 1 Ignition switch in position II. | | | 2 SWITCH ON the rear fog lamp. | | | 3 Measure the voltage between the trailer socket: - 7-pin socket: connector C2003, pin 2, circuit (RD/YE), and ground.
- 13-pin socket: connector C2009, pin 2, circuit (RD/YE), and ground.
| | | Does the meter display battery voltage? Yes Continue fault finding on the trailer. No | | A16: CHECK THE GROUND CONNECTION OF THE REAR FOG LAMP CUT-OFF RELAY | | | 1 Ignition switch in position 0. | | | 2 Disconnect rear fog lamp cut-off relay from socket 2008. | | | 3 Measure the resistance between the rear fog lamp cut-off relay, socket C2008, circuit (BN), wiring harness side and ground. | | | Is the resistance less than 2 Ohm? Yes No LOCATE and RECTIFY the break in the circuit between the rear fog lamp cut-off relay and ground G77 using the Wiring Diagrams. CHECK the operation of the system. | | A17: CHECK THE REAR FOG LAMP CUT-OFF RELAY | | | 1 Use a fused test cable (20 A) to bridge the rear fog lamp cut-off relay, connector C2008, circuit (RD/WH) and circuit (RD/YE), wiring harness side. | | | 2 Ignition switch in position II. | | | 3 SWITCH ON the rear fog lamp. | | | 4 Measure the voltage between the trailer socket: - 7-pin socket: connector C2003, pin 2, circuit (RD/YE), and ground.
- 13-pin socket: connector C2009, pin 2, circuit (RD/YE), and ground.
| | | Does the meter display battery voltage? Yes RENEW the rear fog lamp cut-off relay. CHECK the operation of the system. No LOCATE and RECTIFY the break in the circuit between the rear fog lamp cut-off relay and the trailer socket using the Wiring Diagrams. CHECK the operation of the system. | | PINPOINT TEST B : ONE INDIVIDUAL TRAILER LAMP INOPERATIVE | | TEST CONDITIONS | DETAILS/RESULTS/ACTIONS | | B1: DETERMINE WHICH LAMP IS INOPERATIVE | | | 1 Ignition switch in position II. | | | 2 Check the trailer lamps. | | | Is one of the rear lamps on the trailer inoperative? Yes - Left-hand trailer rear lamp inoperative: GO to B2. - Right-hand trailer rear lamp inoperative: GO to B3. No - Trailer stop lamps inoperative: GO to Pinpoint Test A. - Trailer reversing lamp(s) inoperative: GO to Pinpoint Test A. - Trailer rear fog lamp(s) inoperative: GO to Pinpoint Test A. - Left-hand trailer turn signal lamp inoperative: GO to B4. - Right-hand trailer turn signal lamp inoperative: GO to B6. | | B2: CHECK THE VOLTAGE AT THE TRAILER SOCKET WITH THE SIDE LIGHTS SWITCHED ON | | | 1 SWITCH ON the side lights. | | | 2 Measure the voltage between the trailer socket: - 7-pin socket: connector C2003, pin 7, circuit (OG/WH), and ground.
- 13-pin socket: connector C2009, pin 7, circuit (OG/WH), and ground.
| | | Does the meter display battery voltage? Yes Continue fault finding on the trailer. No LOCATE and RECTIFY the break in the circuit (OG/WH) between intermediate connector C2004, pin 1 and the trailer socket using the Wiring Diagrams. CHECK the operation of the system. | | B3: CHECK THE VOLTAGE AT THE TRAILER SOCKET WITH THE SIDE LIGHTS SWITCHED ON | | | 1 SWITCH ON the side lights. | | | 2 Measure the voltage between the trailer socket: - 7-pin socket: connector C2003, pin 5, circuit (OG), and ground.
- 13-pin socket: connector C2009, pin 5, circuit (OG), and ground.
| | | Does the meter display battery voltage? Yes Continue fault finding on the trailer. No LOCATE and RECTIFY the break in the circuit (OG) between intermediate connector C2006, pin 1 and the trailer socket using the Wiring Diagrams. CHECK the operation of the system. | | B4: CHECK THE VOLTAGE AT THE TRAILER SOCKET WITH THE LEFT-HAND TURN SIGNAL SWITCHED ON | | | 1 Ignition switch in position II. | | | 2 SWITCH ON the left-hand turn signal. | | | 3 Measure the voltage between the trailer socket: - 7-pin socket: connector C2003, pin 1, circuit (BU), and ground.
- 13-pin socket: connector C2009, pin 1, circuit (BU), and ground.
| | | Does the voltage alternate between 0 V and battery voltage? Yes Continue fault finding on the trailer. No | | B5: CHECK THE CIRCUIT BETWEEN THE TRAILER CONTROL UNIT AND THE TRAILER SOCKET | | | 1 Ignition switch in position 0. | | | 2 Disconnect trailer control unit from connector C2002. | | | 3 Measure the resistance between the trailer control unit, connector C2002, pin 7, circuit (BU), wiring harness side and trailer socket: - 7-pin socket: connector C2003, pin 1, circuit (BU).
- 13-pin socket: connector C2009, pin 1, circuit (BU).
| | | Is the resistance less than 2 Ohm? Yes RENEW the trailer control unit. CHECK the operation of the system. No LOCATE and RECTIFY the break in the circuit between the trailer control unit and the trailer socket using the Wiring Diagrams. CHECK the operation of the system. | | B6: CHECK THE VOLTAGE AT THE TRAILER SOCKET WITH THE RIGHT-HAND TURN SIGNAL SWITCHED ON | | | 1 Ignition switch in position II. | | | 2 SWITCH ON the right-hand turn signal. | | | 3 Measure the voltage between the trailer socket: - 7-pin socket: connector C2003, pin 4, circuit (BU/RD), and ground.
- 13-pin socket: connector C2009, pin 4, circuit (BU/RD), and ground.
| | | Does the voltage alternate between 0 V and battery voltage? Yes Continue fault finding on the trailer. No | | B7: CHECK THE CIRCUIT BETWEEN THE TRAILER CONTROL UNIT AND THE TRAILER SOCKET | | | 1 Ignition switch in position 0. | | | 2 Disconnect trailer control unit from connector C2002. | | | 3 Measure the resistance between the trailer control unit, connector C2002, pin 9, circuit (BU/RD), wiring harness side and trailer socket: - 7-pin socket: connector C2003, pin 4, circuit (BU/RD).
- 13-pin socket: connector C2009, pin 4, circuit (BU/RD).
| | | Is the resistance less than 2 Ohm? Yes RENEW the trailer control unit. CHECK the operation of the system. No LOCATE and RECTIFY the break in the circuit between the trailer control unit and the trailer socket using the Wiring Diagrams. CHECK the operation of the system. | | PINPOINT TEST C : TRAILER LAMPS ILLUMINATE CONTINUOUSLY | | TEST CONDITIONS | DETAILS/RESULTS/ACTIONS | | C1: CHECK THE FAULT SYMPTOMS | | | 1 Ignition switch in position II. | | | 2 Check the trailer lamps. | | | Does/do the trailer rear fog lamp(s) illuminate continuously? Yes No - Left-hand trailer rear lamp illuminates continuously: GO to C3. - Right-hand trailer rear lamp illuminates continuously: GO to C4. - Trailer stop lamps illuminate continuously: GO to C5. - Trailer reversing lamps illuminate continuously: GO to C7. - Trailer left-hand turn signal lamp illuminates continuously: GO to C9. - Trailer right-hand turn signal lamp illuminates continuously: GO to C11. - Trailer stop lamps and turn signal lamps illuminate continuously: RENEW the trailer control unit. CHECK the operation of the system. | | C2: CHECK FOR SHORT TO BATTERY VOLTAGE AT THE TRAILER SOCKET (REAR FOG LAMP) | | | 1 Measure the voltage between the trailer socket: - 7-pin socket: connector C2003, pin 2, circuit (RD/YE), and ground.
- 13-pin socket: connector C2009, pin 2, circuit (RD/YE), and ground.
| | | Does the meter display battery voltage? Yes LOCATE and RECTIFY the short to battery voltage in the circuit between the rear fog lamp cut-off relay and the trailer socket using the Wiring Diagrams. CHECK the operation of the system. If necessary RENEW the trailer socket. CHECK the operation of the system. No Continue fault finding on the trailer. | | C3: CHECK FOR SHORT TO BATTERY VOLTAGE ON THE VEHICLE (LEFT-HAND REAR LAMP) | | | 1 Measure the voltage between the trailer socket: - 7-pin socket: connector C2003, pin 7, circuit (OG/WH), and ground.
- 13-pin socket: connector C2009, pin 7, circuit (OG/WH), and ground.
| | | Does the meter display battery voltage? Yes REFER to: Parking, Rear and License Plate Lamps (417-01 Exterior Lighting, Diagnosis and Testing). No Continue fault finding on the trailer. | | C4: CHECK FOR A SHORT TO BATTERY VOLTAGE ON THE VEHICLE (RIGHT-HAND REAR LAMP) | | | 1 Measure the voltage between the trailer socket: - 7-pin socket: connector C2010, pin 5, circuit (OG), and ground.
- 13-pin socket: connector C2012, pin 5, circuit (OG), and ground.
| | | Does the meter display battery voltage? Yes REFER to: Parking, Rear and License Plate Lamps (417-01 Exterior Lighting, Diagnosis and Testing). No Continue fault finding on the trailer. | | C5: CHECK FOR SHORT TO BATTERY VOLTAGE AT THE TRAILER SOCKET (STOP LAMPS) | | | 1 Measure the voltage between the trailer socket: - 7-pin socket: connector C2003, pin 6, circuit (VT), and ground.
- 13-pin socket: connector C2009, pin 6, circuit (VT), and ground.
| | | Does the meter display battery voltage? Yes No Continue fault finding on the trailer. | | C6: NARROW DOWN THE LOCATION OF THE SHORT TO BATTERY VOLTAGE | | | 1 Ignition switch in position 0. | | | 2 Disconnect fuse F59 (20 A) (CJB). | | | 3 Ignition switch in position II. | | | 4 Measure the voltage between the trailer socket: - 7-pin socket: connector C2003, pin 6, circuit (VT), and ground.
- 13-pin socket: connector C2009, pin 6, circuit (VT), and ground.
| | | Does the meter display battery voltage? Yes LOCATE and RECTIFY the short to battery voltage in the circuit between the trailer control unit and the trailer socket using the Wiring Diagrams. CHECK the operation of the system. If necessary RENEW the trailer socket. CHECK the operation of the system. No RENEW the trailer control unit. CHECK the operation of the system. | | C7: CHECK FOR A SHORT TO BATTERY VOLTAGE ON THE VEHICLE (REVERSING LAMP(S) | | | 1 Measure the voltage between the trailer, connector C2009, pin 8, circuit (VT/OG) and ground. | | | Does the meter display battery voltage? Yes No Continue fault finding on the trailer. | | C8: CHECK THE TRAILER RELAY, REVERSING LAMP | | | 1 Ignition switch in position 0. | | | 2 Disconnect fuse F59 (20 A) (CJB). | | | 3 Ignition switch in position II. | | | 4 Measure the voltage between the trailer, connector C2009, pin 8, circuit (VT/OG) and ground. | | | Does the meter display battery voltage? Yes LOCATE and RECTIFY the short to battery voltage in the circuit between the trailer relay, reversing lamp, and the trailer socket using the Wiring Diagrams. CHECK the operation of the system. If necessary RENEW the trailer socket. CHECK the operation of the system. No RENEW the trailer relay, reversing lamp. CHECK the operation of the system. | | C9: CHECK FOR A SHORT TO BATTERY VOLTAGE ON THE VEHICLE (LEFT-HAND TURN SIGNAL LAMP) | | | 1 Measure the voltage between the trailer socket: - 7-pin socket: connector C2003, pin 1, circuit (BU), and ground.
- 13-pin socket: connector C2009, pin 1, circuit (BU), and ground.
| | | Does the meter display battery voltage? Yes No Continue fault finding on the trailer. | | C10: CHECK THE TRAILER CONTROL UNIT | | | 1 Ignition switch in position 0. | | | 2 Disconnect fuse F59 (20 A) (CJB). | | | 3 Ignition switch in position II. | | | 4 Measure the voltage between the trailer socket: - 7-pin socket: connector C2003, pin 1, circuit (BU), and ground.
- 13-pin socket: connector C2009, pin 1, circuit (BU), and ground.
| | | Does the meter display battery voltage? Yes LOCATE and RECTIFY the short to battery voltage in the circuit between the trailer control unit and the trailer socket using the Wiring Diagrams. CHECK the operation of the system. If necessary RENEW the trailer socket. CHECK the operation of the system. No RENEW the trailer control unit. CHECK the operation of the system. | | C11: CHECK FOR A SHORT TO BATTERY VOLTAGE ON THE VEHICLE (RIGHT-HAND TURN SIGNAL LAMP) | | | 1 Measure the voltage between the trailer socket: - 7-pin socket: connector C2003, pin 4, circuit (BU/RD), and ground.
- 13-pin socket: connector C2009, pin 4, circuit (BU/RD), and ground.
| | | Does the meter display battery voltage? Yes No Continue fault finding on the trailer. | | C12: CHECK THE TRAILER CONTROL UNIT | | | 1 Ignition switch in position 0. | | | 2 Disconnect fuse F59 (20 A) (CJB). | | | 3 Ignition switch in position II. | | | 4 Measure the voltage between the trailer socket: - 7-pin socket: connector C2003, pin 4, circuit (BU/RD), and ground.
- 13-pin socket: connector C2009, pin 4, circuit (BU/RD), and ground.
| | | Does the meter display battery voltage? Yes LOCATE and RECTIFY the short to battery voltage in the circuit between the trailer control unit and the trailer socket using the Wiring Diagrams. CHECK the operation of the system. If necessary RENEW the trailer socket. CHECK the operation of the system. No RENEW the trailer control unit. CHECK the operation of the system. | |
