Diagnostic Test

READ AND RECORD DTCS AND ENVIRONMENTAL DATA - ERASE DTCS AND CHECK FOR THE DTC TO RETURN
1. With the scan tool, read DTCs in all Electronic Control Units (ECUs) and record on the repair order.
2. For future reference, with the scan tool, run and save a vehicle Scan Report and all related recorded data.
3. With the scan tool, erase all DTCs.
4. Turn the ignition off for a minimum of 10.0 seconds.
5. Turn the ignition on.
6. Using the When Monitored and Set Conditions above and recorded data, operate the vehicle in the conditions that set the DTC.
7. With the scan tool, read DTCs.
  Did the DTC return?
  
  Yes
  - Go to 2
  No
  - Perform the INTERMITTENT CONDITION diagnostic procedure. Refer to INTERMITTENT CONDITION .
CHECK THE BRAKE SWITCH SIGNALS
1. Turn the ignition on.
2. With the scan tool, monitor both Brake Signals with the brake pedal not pressed.
3. Press and release the Brake Pedal while monitoring the state of both signals.
  NOTE:
  Either Brake Signal 1 stuck off or Brake Signal 2 stuck on can cause this DTC.
  
  Is Brake Signal 1 stuck off (not pressed) or Brake Signal 2 stuck on (pressed)?
  
  Yes, Brake Signal 1 is stuck off
  - Go to 3
  Yes, Brake Signal 2 is stuck on
  - Go to 7
  No
  - Perform the INTERMITTENT CONDITION diagnostic procedure. Refer to INTERMITTENT CONDITION .
CHECK THE (A938) FUSED B+ CIRCUIT FOR AN OPEN
1. Turn the ignition off.
2. Disconnect the Brake Switch harness connector.
3. Turn the ignition on.
4. Measure the voltage on the (A938) Fused B+ circuit at the Brake Switch harness connector.
  Is the voltage equal to Battery voltage?
  
  Yes
  - Go to 4
  No
  - Repair the (A938) Fused B+ circuit for an open. If the fuse is open, check the (A938) Fused B+ circuit and Brake Switch (B135) Signal 1 circuit for a short to ground.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK THE BRAKE SWITCH FOR PROPER OPERATION
NOTE:
Brake Signal 1 is normally open inside the switch. The switch can be checked one of two ways below.
1. Measure the resistance between terminals 1 and 4 of the Brake Switch while pressing and releasing the Brake Pedal and monitor for continuity through the switch in each state (should be open when NOT PRESSED and continuity when PRESSED).
2. Reconnect the Brake Switch harness connector. Back probe and measure the voltage on the Brake Switch (B135) Signal 1 circuit at the Brake Switch harness connector while pressing and releasing the Brake Pedal. (should have 0 volts when NOT PRESSED and 12 volts when PRESSED).
  Is the Brake Switch functioning properly?
  
  Yes
  - Go to 5
  No
  - Verify that there is good pin to terminal contact in the Brake Switch and Powertrain Control Module harness connectors. If no problems are found, replace the Brake Switch. Refer to SWITCH, STOP LAMP, REMOVAL AND INSTALLATION .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK THE BRAKE SWITCH (B135) SIGNAL 1 CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Turn the ignition off.
2. Disconnect the Brake Switch harness connector.
3. Disconnect the PCM C1 harness connector.
  CAUTION:
  Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install the GPEC Diagnostic Adaptor to perform the diagnosis.
4. Connect the (special tool #10436, Adapter, GPEC Diagnostic)to the appropriate PCM connector.
5. Measure the resistance of the Brake Switch (B135) Signal 1 circuit between the Brake Switch harness connector and the GPEC Adaptor.
  Is the resistance below 5.0 Ohms?
  
  Yes
  - Go to 6
  No
  - Repair the Brake Switch (B135) Signal 1 circuit for an open or high resistance.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK RELATED PCM AND COMPONENT CONNECTIONS
1. Perform any Service Bulletins that apply.
2. Disconnect all PCM harness connectors.
3. Disconnect all related in-line harness connections (if equipped).
4. Disconnect the related component harness connectors.
5. Inspect harness connectors, component connectors, and all male and female terminals for the following conditions:
  - Proper connector installation.
  - Damaged connector locks.
  - Corrosion.
  - Other signs of water intrusion.
  - Weather seal damage (if equipped).
  - Bent terminals.
  - Overheating due to a poor connection (terminal may be discolored due to excessive current draw).
  - Terminals that have been pushed back into the connector cavity.
  - Check for spread terminals and verify proper terminal tension.
  Repair any conditions that are found.
6. Reconnect all PCM harness connectors. Be certain that all harness connectors are fully seated and the connector locks are fully engaged.
7. Reconnect all in-line harness connectors (if equipped). Be certain that all connectors are fully seated and the connector locks are fully engaged.
8. Reconnect all related component harness connectors. Be certain that all connectors are fully seated and the connector locks are fully engaged.
9. With the scan tool, erase DTCs.
10. Test drive or operate the vehicle in accordance with the when monitored and set conditions.
11. With the scan tool, read DTCs.
  Did the DTC return?
  
  Yes
  - Replace and program the Powertrain Control Module (PCM) in accordance with the Service Information. Refer to MODULE, POWERTRAIN CONTROL (PCM), REMOVAL AND INSTALLATION .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
  No
  - The wiring or poor connection problem has been repaired.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK THE (F944) FUSED IGNITION SWITCH OUTPUT CIRCUIT FOR AN OPEN
1. Turn the ignition off.
2. Disconnect the Brake Switch harness connector.
3. Turn the ignition on.
4. Measure the voltage on the (F944) Fused Ignition Switch Output circuit at the Brake Switch harness connector.
  Is the voltage equal to Battery voltage?
  
  Yes
  - Go to 8
  No
  - Repair the (F944) Fused Ignition Switch Output circuit for an open. If the fuse is open, check the (F944) Fused Ignition Switch Output circuit and Brake Switch (B134) Signal 2 circuit for a short to ground.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK THE BRAKE SWITCH FOR PROPER OPERATION
NOTE:
Brake Signal 2 is normally closed inside the switch. The switch can be checked one of two ways below.
1. Measure the resistance between terminals 2 and 3 of the Brake Switch while pressing and releasing the Brake Pedal and monitor for continuity through the switch in each state (should have continuity when NOT PRESSED and be open when PRESSED).
2. Reconnect the Brake Switch harness connector. Back probe and measure the voltage on the Brake Switch (B134) Signal 2 circuit at the Brake Switch harness connector while pressing and releasing the Brake Pedal. (should have 12 volts when NOT PRESSED and 0 volts when PRESSED).
  Is the Brake Switch functioning properly?
  
  Yes
  - Go to 9
  No
  - Verify that there is good pin to terminal contact in the Brake Switch and Powertrain Control Module harness connectors. If no problems are found, replace the Brake Switch. Refer to SWITCH, STOP LAMP, REMOVAL AND INSTALLATION .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK THE BRAKE SWITCH (B134) SIGNAL 2 CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Turn the ignition off.
2. Disconnect the Brake Switch harness connector.
3. Disconnect the BCM harness connector.
4. Measure the resistance of the Brake Switch (B134) Signal 2 circuit between the Brake Switch harness connector and the appropriate BCM harness connector.
  Is the resistance below 5.0 Ohms?
  
  Yes
  - Go to 10
  No
  - Repair the Brake Switch (B134) Signal 2 circuit for an open or high resistance.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST .
CHECK RELATED BCM AND COMPONENT CONNECTIONS
1. Disconnect all BCM harness connectors.
2. Disconnect all related in-line harness connections (if equipped).
3. Disconnect the related component harness connectors.
4. Inspect harness connectors, component connectors, and all male and female terminals for the following conditions:
  - Proper connector installation.
  - Damaged connector locks.
  - Corrosion.
  - Other signs of water intrusion.
  - Weather seal damage (if equipped).
  - Bent terminals.
  - Overheating due to a poor connection (terminal may be discolored due to excessive current draw).
  - Terminals that have been pushed back into the connector cavity.
  - Check for spread terminals and verify proper terminal tension.
  Repair any conditions that are found.
5. Reconnect all BCM harness connectors. Be certain that all harness connectors are fully seated and the connector locks are fully engaged.
6. Reconnect all in-line harness connectors (if equipped). Be certain that all connectors are fully seated and the connector locks are fully engaged.
7. Reconnect all related component harness connectors. Be certain that all connectors are fully seated and the connector locks are fully engaged.
8. With the scan tool, erase DTCs.
9. Test drive or operate the vehicle in accordance with the when monitored and set conditions.
10. With the scan tool, read DTCs.
  Did the DTC return?
  
  Yes
  - 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 BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  No
  - The wiring or poor connection problem has been repaired.
  - Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .