Diagnostic Test

CHECK FOR AN ACTIVE DTC
1. Turn the ignition on.
2. Apply the Brake Pedal.
3. With the scan tool, read the Body Control Module (BCM) DTCs and record on the repair order.
  Is the DTC active?
  
  Yes
  - Go To 2
  No
  - The condition or conditions that originally set this DTC are not present at this time. Using the wiring diagrams as a guide, check all related splices and connectors for signs of water intrusion, corrosion, pushed out or bent terminals and correct pin tension. If no problems are found, test complete.
  - Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
CHECK THE (L51) BRAKE LAMP SWITCH OUTPUT CIRCUIT FOR A SHORT TO VOLTAGE
NOTE:
Make sure the brake pedal is not applied while performing this step.
1. Turn the ignition off.
2. Disconnect the Center High Mounted Stop Lamp harness connector.
3. Turn the ignition on.
4. Measure the voltage between ground and the (L51) Brake Lamp Switch Output circuit at the Center High Mounted Stop Lamp harness connector.
  Is there any voltage present?
  
  Yes
  - Repair the short to voltage in the (L51) Brake Lamp Switch Output circuit.
  - Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  No
  - Go To 3
CHECK THE (L51) BRAKE LAMP SWITCH OUTPUT CIRCUIT FOR AN OPEN
1. Turn the ignition off.
2. Disconnect the BCM C6/F harness connector.
3. Measure the resistance of the (L51) Brake Lamp Switch Output circuit between the Center High Mounted Stop Lamp harness connector and the BCM C6/F harness connector.
  Is the resistance above 3.0 Ohms?
  
  Yes
  - Repair the open in the (L51) Brake Lamp Switch Output circuit.
  - Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  No
  - Go To 4
CHECK THE (Z912) GROUND CIRCUIT FOR AN OPEN
1. Measure the resistance between ground and the (Z912) Ground circuit at the Center High Mounted Stop Lamp harness connector.
  Is the resistance above 3.0 Ohms?
  
  Yes
  - Repair the open in the (Z912) Ground circuit.
  - Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  No
  - Go To 5
CHECK THE BCM
1. Turn the ignition off.
2. Reconnect the BCM C6/F harness connector.
3. Turn the ignition on.
4. Apply the Brake Pedal.
  NOTE:
  The test light must illuminate brightly. Compare the brightness to that of a direct connection to the battery.
5. Connect a 12-volt test light between the (L51) Brake Lamp Switch Output circuit and the (Z912) Ground circuit at the Center High Mounted Stop Lamp harness connector.
  Does the test light illuminate brightly?
  
  Yes
  - Replace the Center High Mounted Stop Lamp Bulb in accordance with the Service Information. Refer to LAMP, CENTER HIGH MOUNTED STOP, REMOVAL .
  - Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  No
  - Replace the Body Control Module (BCM) in accordance with the Service Information. Refer to MODULE, BODY CONTROL (BCM), REMOVAL .
  - Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .