| Diagnosis and Testing Special Tool(s) | | 73III Automotive Meter 105-R0057 or equivalent | | | Vehicle Communication Module (VCM) and Integrated Diagnostic System (IDS) software with appropriate hardware, or equivalent scan tool | | | Flex Probe Kit 105-R025C or equivalent | Principles of Operation The smart junction box (SJB) monitors the input from the brake pedal position (BPP) switch. When the brake pedal is applied, voltage is routed to the SJB and the high mounted stoplamp. The SJB then supplies voltage to the rear stoplamps. The SJB utilizes a protective circuit strategy for many of its outputs (for example, the headlamp output circuit). Output loads (current level) are monitored for excessive current (typically short circuits) and are shut down (turns off the voltage or ground provided by the module) when a fault is detected. A continuous diagnostic trouble code (DTC) is stored at that time for the fault. The circuit will then reset after an ignition cycle or customer demand of the function (switching the component on, 30-minute battery saver being energized). When an excessive circuit load occurs several times, the module shuts down the output until a service procedure is performed. At the same time, the continuous DTC that was stored on the first failure will not clear by a command to clear the continuous DTCs. The module will not allow this code to be cleared or the circuit restored to normal until a successful on-demand self-test proves that the fault has been repaired. After the on-demand self-test has successfully completed (no on-demand DTCs present), the continuous DTC will have been cleared and the circuit function will return. Inspection and Verification - Verify the customer concern.
- Visually inspect the following for obvious signs of mechanical or electrical damage.
Visual Inspection Chart | Mechanical | Electrical | - Brake pedal position (BPP) switch
| - Smart junction box (SJB) fuse(s):
- SJB
- Bulb(s)
- Circuitry
| - If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to the next step.
NOTE:Make sure the multifunction switch is in the OFF position. NOTE:Make sure the multifunction switch is in the LOW BEAM position. -
NOTE:Make sure to use the latest scan tool software release. If the cause is not visually evident, connect the scan tool to the data link connector (DLC). -
NOTE:The vehicle communication module (VCM) LED prove-out confirms power and ground from the DLC are provided to the VCM. If the scan tool does not communicate with the VCM: - Check the VCM connection to the vehicle.
- Check the scan tool connection to the VCM.
- If the scan tool does not communicate with the vehicle:
- Verify the ignition key is in the ON position.
- Verify the scan tool operation with a known good vehicle.
- Carry out the network test:
- If the network test passes, retrieve and record the continuous memory DTCs.
- Clear the continuous DTCs and carry out the self-test diagnostics for the SJB.
- If the DTCs retrieved are related to the concern, go to the Smart Junction Box (SJB) Diagnostic Trouble Code (DTC) Index. For all other DTCs, refer to Section 419-10 Multifunction Electronic Modules.
- If no DTCs related to the concern are retrieved, GO to Symptom Chart.
Smart Junction Box (SJB) Diagnostic Trouble Code (DTC) Index Symptom Chart Symptom Chart | Symptom | Possible Sources | Action | | The stoplamps are inoperative | * Fuse * Circuitry * Brake pedal position (BPP) switch * Smart junction box (SJB) | * | | One or more stoplamps are inoperative | * Circuitry * High mounted stoplamp * SJB | * | | The stoplamps are on continuously | * Circuitry * BPP switch * Speed control actuator * Anti-lock brake system (ABS) module * Powertrain control module (PCM) * SJB | * | Pinpoint Tests Pinpoint Test H: The Stoplamps Are Inoperative Refer to Wiring Diagrams Cell 90, for schematic and connector information. Normal Operation The brake pedal position (BPP) switch is supplied battery voltage through circuit 10 (LG/RD) from the smart junction box (SJB). When the brake pedal is applied, the BPP switch allows voltage to flow through circuit 511 (LG). Circuit 511 (LG) sends voltage to the high mounted stoplamp and the SJB, which in turn provides voltage to the LH and RH rear lamps. Possible Causes - Fuse
- Circuit 10 (LG/RD) open
- Circuit 511 (LG) open
- BPP switch
- SJB
| PINPOINT TEST A : THE STOPLAMPS ARE INOPERATIVE | CAUTION:Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector. | | TEST CONDITIONS | DETAILS/RESULTS/ACTIONS | | A1: CHECK CIRCUIT 10 (LG/RD) FOR VOLTAGE | | | 1 Ignition switch in position 0. | | | 2 Disconnect BPP Switch . | | | 3 Measure the voltage between the BPP switch C278-2, circuit 10 (LG/RD), harness side and ground. | | | Is the voltage greater than 10 volts? Yes No VERIFY the SJB fuse 6 (15A) is OK. If OK, GO to A3. . | | A2: CHECK THE BPP SWITCH | | | 1 Connect a fused (15A) jumper wire between the BPP switch C278-2, circuit 10 (LG/RD), harness side and the BPP switch C278-1, circuit 511 (LG), harness side. | | | Are the stoplamps illuminated? Yes INSTALL a new BPP switch. REFER to Stoplamp Switch in this section. TEST the system for normal operation. No REPAIR circuit 511 (LG). TEST the system for normal operation. | | A3: CHECK CIRCUIT 10 (RD/LG) FOR AN OPEN | | | 1 Disconnect SJB . | | | 2 Measure the resistance between the SJB C2280c-17, circuit 10 (LG/RD), harness side and the BPP switch C278-2, circuit 10 (LG/RD), harness side. | | | Is the resistance less than 5 ohms? Yes No REPAIR the circuit. TEST the system for normal operation. | | A4: CHECK FOR CORRECT SJB OPERATION | | | 1 Disconnect all the SJB connectors. | | | 2 Check for: | | | 3 Connect all the SJB connectors and make sure they seat correctly. | | | 4 Operate the system and verify the concern is still present. | | | Is the concern still present? Yes No The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test. | Pinpoint Test I: One Or More Stoplamps Are Inoperative Refer to Wiring Diagrams Cell 90, for schematic and connector information. Normal Operation When the brake pedal is applied, the brake pedal position switch (BPP) switch routes voltage through circuit 511 (LG). Circuit 511 (LG) provides voltage to the high mounted stoplamp and the smart junction box (SJB). The SJB then provides voltage to the LH and RH rear lamps through circuits 22 (LB/BK) and 810 (RD/LG), respectively. All the stoplamps are provided ground through circuit 57 (BK). Possible Causes - Circuit 22 (LB/BK) open or short to ground
- Circuit 57 (BK) open
- Circuit 511 (LG) open
- Circuit 810 (RD/LG) open or short to ground
- High mounted stoplamp
- SJB
| PINPOINT TEST B : ONE OR MORE STOPLAMPS ARE INOPERATIVE | CAUTION:Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector. | | TEST CONDITIONS | DETAILS/RESULTS/ACTIONS | | B1: DETERMINE THE INOPERATIVE STOPLAMP | | | 1 Apply the brake pedal. | | | 2 Verify which stoplamp is inoperative. | | | Is only the high mounted stoplamp inoperative? Yes No If one rear stoplamp is inoperative, GO to B4. .If both rear stoplamps are inoperative, GO to B7. . | | B2: CHECK CIRCUIT 511 (LG) FOR AN OPEN | | | 1 Disconnect High Mounted Stoplamp . | | | 2 Measure the voltage between the high mounted stoplamp C475-2, circuit 511 (DG), harness side and ground while applying the brake pedal. | | | Is the voltage greater than 10 volts? Yes No REPAIR the circuit. TEST the system for normal operation. | | B3: CHECK CIRCUIT 57 (BK) FOR AN OPEN (HIGH MOUNTED STOPLAMP) | | | 1 Measure the resistance between the high mounted stoplamp C475-1, circuit 57 (BK), harness side and ground. | | | Is the resistance less than 5 ohms? Yes INSTALL a new high mounted stoplamp. TEST the system for normal operation. No REPAIR the circuit. TEST the system for normal operation. | | B4: CHECK CIRCUIT 57 (BK) FOR AN OPEN (REAR STOPLAMP) | | | 1 Ignition switch in position II. | | | 2 Place the multifunction switch in the PARKING LAMPS ON position. | | | Does the rear lamp in question illuminate? Yes No REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test. | | B5: CHECK CIRCUIT 22 (LB/BK) FOR AN OPEN OR A SHORT TO GROUND | | | 1 Ignition switch in position 0. | | | 2 Disconnect SJB . | | | 3 Measure the resistance between the LH rear lamp C419-3, circuit 22 (LB/BK), harness side and the SJB C2280c-22, circuit 22 (LB/BK), harness side; and between the LH rear lamp C419-3, circuit 22 (LB/BK), harness side and ground. | | | Is the resistance less than 5 ohms between the LH rear lamp and the SJB, and greater than 10,000 ohms between the LH rear lamp and ground? Yes No REPAIR the circuit. RUN the on-demand self test (required to clear certain DTCs). CORRECT any unresolved DTCs. CLEAR all DTCs. TEST the system for normal operation. | | B6: CHECK CIRCUIT 810 (RD/LG) FOR AN OPEN OR A SHORT TO GROUND | | | 1 Ignition switch in position 0. | | | 2 Disconnect SJB . | | | 3 Measure the resistance between the RH rear lamp C418-3, circuit 810 (RD/LG), harness side and the SJB C2280c-26, circuit 810 (RD/LG), harness side; and between the RH rear lamp C418-3, circuit 810 (RD/LG), harness side and ground. | | | Is the resistance less than 5 ohms between the RH rear lamp and the SJB, and greater than 10,000 ohms between the RH rear lamp and ground? Yes No REPAIR the circuit. RUN the on-demand self test (required to clear certain DTCs). CORRECT any unresolved DTCs. CLEAR all DTCs. TEST the system for normal operation. | | B7: CHECK CIRCUIT 511 (LG) FOR AN OPEN | | | 1 Ignition switch in position 0. | | | 2 Disconnect SJB . | | | 3 Disconnect BPP Switch . | | | 4 Measure the resistance between the BPP switch C278-1, circuit 511 (LG), harness side and the SJB C2280c-14, circuit 511 (LG), harness side. | | | Is the resistance less than 5 ohms? Yes No REPAIR the circuit. TEST the system for normal operation. | | B8: CHECK FOR CORRECT SJB OPERATION | | | 1 Disconnect all the SJB connectors. | | | 2 Check for: | | | 3 Connect all the SJB connectors and make sure they seat correctly. | | | 4 Operate the system and verify the concern is still present. | | | Is the concern still present? Yes No The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test. | Pinpoint Test J: The Stoplamps Are On Continuously Refer to Wiring Diagrams Cell 90, for schematic and connector information. Normal Operation When the brake pedal is applied, the brake pedal position (BPP) switch allows voltage to flow through circuit 511 (LG). Circuit 511 (LG) provides voltage to the high mounted stoplamp, the speed control module, the powertrain control module (PCM), the anti-lock brake system (ABS) module and the smart junction box (SJB). The SJB then provides voltage to the LH and RH rear lamps through circuits 22 (LB/BK) and 810 (RD/LG), respectively. Possible Causes - Circuit 22 (LB/BK) short to voltage
- Circuit 511 (LG) short to voltage
- Circuit 810 (RD/LG) short to voltage
- BPP switch
- Speed control actuator
- SJB
- PCM
- ABS module
| PINPOINT TEST C : THE STOPLAMPS ARE ON CONTINUOUSLY | | TEST CONDITIONS | DETAILS/RESULTS/ACTIONS | | C1: DETERMINE IF ALL STOPLAMPS ARE ILLUMINATED | | | 1 Observe the operation of the stoplamps with the brake pedal released. | | | Are all of the stoplamps illuminated? Yes No | | C2: CHECK THE BPP SWITCH | | | 1 Ignition switch in position 0. | | | 2 Disconnect BPP Switch . | | | Do the stoplamps continue to illuminate? Yes No INSTALL a new BPP switch. REFER to Stoplamp Switch in this section. TEST the system for normal operation. | | C3: CHECK THE PCM | | | 1 Disconnect PCM . | | | Do the stoplamps continue to illuminate? Yes No | | C4: CHECK THE ABS MODULE | | | 1 Disconnect ABS Module . | | | Do the stoplamps continue to illuminate? Yes If equipped with speed control, GO to C5. .If not equipped with speed control, GO to C6. . No | | C5: CHECK THE SPEED CONTROL ACTUATOR | | | 1 Disconnect Speed Control Actuator . | | | Do the stoplamps continue to illuminate? Yes No | | C6: CHECK THE SJB | | | 1 Disconnect SJB . | | | Do the stoplamps continue to illuminate? Yes If the high mounted stoplamp continues to illuminate, REPAIR circuit 511 (LG). CLEAR the DTCs. REPEAT the self-test.If the LH rear lamp continues to illuminate, REPAIR circuit 22 (LB/BK). CLEAR the DTCs. REPEAT the self-test.If the RH rear lamp continues to illuminate, REPAIR circuit 810 (RD/LG). CLEAR the DTCs. REPEAT the self-test. No | | C7: CHECK FOR CORRECT PCM OPERATION | | | 1 Disconnect all the PCM connectors. | | | 2 Check for: | | | 3 Connect all the PCM connectors and make sure they seat correctly. | | | 4 Operate the system and verify the concern is still present. | | | Is the concern still present? Yes No The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test. | | C8: CHECK FOR CORRECT ABS MODULE OPERATION | | | 1 Disconnect the ABS module connector. | | | 2 Check for: | | | 3 Connect the ABS module connector and make sure it seats correctly. | | | 4 Operate the system and verify the concern is still present. | | | Is the concern still present? Yes No The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test. | | C9: CHECK FOR CORRECT SPEED CONTROL ACTUATOR OPERATION | | | 1 Disconnect the speed control actuator connector. | | | 2 Check for: | | | 3 Connect the speed control actuator connector and make sure it seats correctly. | | | 4 Operate the system and verify the concern is still present. | | | Is the concern still present? Yes INSTALL a new speed control actuator. REFER to Section 310-03 Speed Control. TEST the system for normal operation. No The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test. | | C10: CHECK FOR CORRECT SJB OPERATION | | | 1 Disconnect all the SJB connectors. | | | 2 Check for: | | | 3 Connect all the SJB connectors and make sure they seat correctly. | | | 4 Operate the system and verify the concern is still present. | | | Is the concern still present? Yes No The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test. | |
