Diagnostic Test

CHECK FOR AN ACTIVE DTC
1. Turn the ignition on.
2. Press and release the Brake Pedal several times.
3. With the scan tool, read DTCs and record on the repair order.
  Is the DTC active or pending?
  
  Yes
  - Go To 2
  No
  - Perform the INTERMITTENT CONDITION diagnostic procedure. Refer to INTERMITTENT CONDITION .
    NOTE:
    A Brake Switch that is out of adjustment and is momentarily reading pressed while driving can cause this DTC to set. Check the Brake Switch for proper adjustment.
DETERMINE WHICH BRAKE SWITCH SIGNAL IS ERRONEOUS
1. Turn the ignition on.
2. While monitoring the states of Brake Signal 1 and Brake Signal 2 on the scan tool, press and release the brake pedal several times.
  NOTE:
  It may be helpful to wiggle the Brake Pedal slightly while monitoring the inputs to determine if the switch adjustment is not correct.
  
  Which of the brake signals is missing?
  
  Brake Signal 1
  - Go To 3
  Brake Signal 2
  - Go To 7
CHECK THE (B135) BRAKE SIGNAL 1 CIRCUIT FOR A SHORT TO VOLTAGE
1. Disconnect the Brake Switch harness connector.
2. Measure for voltage on the (B135) Brake Signal 1 circuit at the Brake Switch harness connector.
  Is there any voltage present?
  
  Yes
  - Repair the (B135) Brake Signal 1 circuit for a short to voltage.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Go To 4
CHECK THE (B135) BRAKE SIGNAL 1 CIRCUIT FOR A SHORT TO GROUND
1. Turn the ignition off.
2. Disconnect the BCM C4 harness connector.
3. Check for continuity between ground and the (B135) Brake Signal 1 circuit in the Brake Switch harness connector.
  Is there continuity between ground and the (B135) Brake Signal 1 circuit?
  
  Yes
  - Repair the (B135) Brake Signal 1 circuit for a short to ground.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Go To 5
CHECK THE (B135) BRAKE SIGNAL 1 CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Measure the resistance of the (B135) Brake Signal 1 circuit between the Brake Switch harness connector and the BCM C4 harness connector.
  Is the resistance below 3.0 Ohms?
  
  Yes
  - Go To 6
  No
  - Repair the (B135) Brake Signal 1 circuit for an open or high resistance.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK THE (A938) STOP LAMP SWITCH BATTERY FEED CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Disconnect the PDC C3 harness connector.
2. Measure the resistance of the (A938) Stop Lamp Switch Battery Feed circuit between the Brake Switch harness connector and the PDC C3 harness connector.
  Is the resistance below 3.0 Ohms?
  
  Yes
  - Go To 11
  No
  - Repair the (A938) Stop Lamp Switch Battery Feed circuit for an open or high resistance.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK THE (B134) BRAKE SIGNAL 2 CIRCUIT FOR A SHORT TO VOLTAGE
1. Disconnect the Brake Switch harness connector.
2. Measure for voltage on the (B134) Brake Signal 2 circuit at the Brake Switch harness connector.
  Is there any voltage present?
  
  Yes
  - Repair the (B134) Brake Signal 2 circuit for a short to voltage.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Go To 8
CHECK THE (B134) BRAKE SIGNAL 2 CIRCUIT FOR A SHORT TO GROUND
1. Turn the ignition off.
2. Disconnect the BCM C4 harness connector.
3. 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 .
  No
  - Go To 9
CHECK THE (B134) BRAKE SIGNAL 2 CIRCUIT FOR AN OPEN/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 3.0 Ohms?
  
  Yes
  - Go To 10
  No
  - Repair the (B134) Brake Signal 2 circuit for an open or high resistance.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK THE (F944) FUSED IGNITION SWITCH OUTPUT (RUN-START) CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Measure the resistance of the (F944) Fused Ignition Switch Output (Run-Start) circuit between the Stop Lamp Switch harness connector and the BCM C4 harness connector.
  Is the resistance below 3.0 Ohms?
  
  Yes
  - Go To 11
  No
  - Repair the (F944) Fused Ignition Switch Output (Run-Start) circuit for an open or high resistance. Inspect the related fuse. If the fuse is open, check the circuit for a short to ground.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
BRAKE SWITCH
1. Replace the Brake Switch in accordance with the Service Information.
2. Turn the ignition on.
3. With the scan tool, erase DTCs.
4. Press and release the Brake Pedal several times.
  NOTE:
  It may be helpful to wiggle the Brake Pedal slightly while monitoring the inputs to determine if the switch adjustment is not correct.
5. With the scan tool, read DTCs.
  Did the DTC return?
  
  Yes
  - Go To 12
  No
  - Repair complete.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
BODY CONTROL MODULE (BCM)
1. Using appropriate SYSTEM WIRING DIAGRAMS/schematic as a guide, inspect the wiring and connectors between the Brake Switch and the Body Control Module (BCM).
2. Look for any chafed, pierced, pinched or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals.
4. Perform any Service Bulletins that may apply.
  Were any problems found?
  
  Yes
  - Repair as necessary.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - Replace and program the Body Control Module (BCM) in accordance with the Service Information.
    Refer to MODULE, BODY CONTROL (BCM), REMOVAL AND INSTALLATION .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .