Diagnostic Test

WARNING: This page is about a different car, the 2017 Jeep Cherokee. However, it is still accessible from the selected car via links, so may be relevant.

CHECK BODY CONTROL MODULE (BCM) DTCs
1. Turn the ignition on.
2. With the scan tool, read DTCs in the BCM.
  Are there any BCM Stop Lamp Switch related DTCs present?
  
  Yes
  - Perform the appropriate diagnostic procedure. Refer to BODY CONTROL MODULE (BCM) - DIAGNOSTIC CODE INDEX .
  No
  - Go To 2
CHECK POWERTRAIN CONTROL MODULE (PCM) DTCs
1. Turn the ignition on.
2. With the scan tool, read DTCs in the PCM.
  Are there any PCM Stop Lamp Switch related DTCs present?
  
  Yes
  - Perform the appropriate diagnostic procedure. For 2.4L, refer to 2.4L - DIAGNOSTIC CODE INDEX . For 3.2L, refer to 3.2L - DIAGNOSTIC CODE INDEX .
  No
  - Go To 3
STOP LAMP SWITCH OPERATION
1. Start the engine.
2. Using the scan tool, monitor the brake pedal switch status while pressing the brake pedal and releasing.
  Is the Stop Lamp Switch operating correctly?
  
  Yes
  - Go To 4
  No
  - Go To 5
BRAKE PEDAL PRESSURE
1. Using the scan tool, monitor the brake pedal pressure and the status of the brake pedal switch while slowly pressing the brake pedal.
  Was there Brake Pressure before the Brake Pedal Switch status changed?
  
  Yes
  - Check for correct Stop Lamp Switch Installation. Refer to SWITCH, STOP LAMP, INSTALLATION .
  No
  - Perform the INTERMITTENT CONDITION diagnostic procedure. For 2.4L, refer to INTERMITTENT CONDITION . For 3.2L, refer to INTERMITTENT CONDITION .
(B134) BRAKE SIGNAL 2 CIRCUIT
1. Turn the ignition off.
2. Disconnect the Stop Lamp Switch harness connector.
3. Using a 12-volt test light connected to 12 volts, check the (B134) Brake Signal 2 circuit at the Stop Lamp Switch harness connector while pressing and releasing the brake pedal several times.
  Does the test light change from illuminated to not illuminated as the brake pedal is pressed and released?
  
  Yes
  - Go To 6
  No
  - Go To 7
(B135) BRAKE SIGNAL 1 CIRCUIT
1. Turn the ignition on.
2. Using a 12-volt test light connected to ground, check the (B135) Brake Signal 1 circuit at the Stop Lamp Switch harness connector while pressing and releasing the brake pedal several times.
  Does the test light change from illuminated to not illuminated as the brake pedal is pressed and released?
  
  Yes
  - Go To 11
  No
  - Go To 9
CHECK THE (B134) BRAKE SIGNAL 2 CIRCUIT FOR A SHORT TO GROUND
1. Disconnect the BCM C4 harness connector.
2. Check for continuity between ground and the (B134) Brake Signal 2 circuit at the Stop Lamp Switch harness connector.
  Is there continuity between ground and the (B134) Brake Signal 2 circuit?
  
  Yes
  - Repair the (B134) Brake Signal 2 circuit for a short to ground.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 2.4L or POWERTRAIN VERIFICATION TEST, 3.2L . .
  No
  - Go To 8
(B134) BRAKE SIGNAL 2 CIRCUIT OPEN OR HIGH RESISTANCE
1. Measure the resistance of the (B134) Brake Signal 2 circuit between the Stop Lamp Switch harness connector and the BCM C4 harness connector.
  Is the resistance below 5.0 ohms?
  
  Yes
  - Go To 10
  No
  - Repair the (B134) Brake Signal 2 circuit for an open or high resistance.
  - Perform the PCM VERIFICATION Test. Refer to POWERTRAIN VERIFICATION TEST, 2.4L or POWERTRAIN VERIFICATION TEST, 3.2L . .
(B135) BRAKE SIGNAL 1 CIRCUIT SHORTED TO VOLTAGE
1. Measure the voltage of the (B135) Brake Signal 1 circuit in the Stop Lamp Switch harness connector.
  Is there any voltage present?
  
  Yes
  - Repair the (B135) Brake Signal 1 circuit for a short to voltage.
  - Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  No
  - Go To 10
STOP LAMP SWITCH
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Stop Lamp Switch and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched, or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals.
4. Refer to any Technical Service Bulletins that may apply.
5. Replace the Stop Lamp Switch in accordance with the Service Information. Refer to SWITCH, STOP LAMP, REMOVAL . Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
6. With the scan tool, read DTCs in the ABS Module.
  Does the DTC remain active?
  
  Yes
  - Go To 11
  No
  - Replace the Stop Lamp Switch in accordance with the Service Information. Refer to SWITCH, STOP LAMP, REMOVAL .
  - Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
ANTI-LOCK BRAKE SYSTEM (ABS) MODULE
1. With the scan tool, erase DTCs in the ABS Module.
2. Press and release the brake pedal.
3. With the scan tool, read DTCs in the ABS Module.
  Does the DTC remain active?
  
  Yes
  - Replace the Anti-lock Brake System (ABS) Module in accordance with the Service Information. Refer to MODULE, ANTI-LOCK BRAKE SYSTEM (ABS), REMOVAL .
  - Perform the ABS VERIFICATION TEST. Refer to ABS VERIFICATION TEST .
  No
  - Test Complete.
  - Perform the ABS VERIFICATION TEST. Refer to ABS VERIFICATION TEST .