Diagnostic Test

CHECK FOR AN INTERMITTENT CONDITION
1. Turn the ignition on.
2. With the scan tool, clear all DTCs.
3. Activate the Stop Lamps.
4. With the scan tool, read DTCs.
  Does the scan tool display this DTC as active?
  
  Yes
  - Go To 2
  No
  - Test complete. 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.
  - Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
CHECK THE CENTER HIGH MOUNTED STOP LAMP (CHMSL) BULBS
NOTE:
This DTC will set if all CHMSL bulbs are disconnected or bunt out.
1. Inspect the harness connector at the CHMSL for correct connection.
2. Inspect the CHMSL for burnt out or damaged bulbs.
  Are any concerns present?
  
  Yes
  - Replace the CHMSL Bulb or Lamp as needed in accordance with the Service Information.
  - Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  No
  - Go To 3
CHECK THE (Z941) GROUND CIRCUIT FOR AN OPEN
1. Turn the ignition off.
2. Disconnect the CHMSL harness connector.
3. Measure the resistance of the (Z941) Ground circuit at the CHMSL harness connector.
  Is the resistance below 5.0 Ohms?
  
  Yes
  - Go To 4
  No
  - Repair the open in the (Z941) Ground circuit.
  - Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
CHECK THE (L56) BRAKE LAMP SWITCH OUTPUT CIRCUIT FOR AN OPEN
1. Disconnect the BCM C3 harness connector.
2. Measure the resistance of the (L56) Brake Lamp Switch Output circuit between the CHMSL harness connector and the BCM C3 harness connector.
  Is the resistance below 5.0 Ohms?
  
  Yes
  - Go To 5
  No
  - Repair the open in the (L56) Brake Lamp Switch Output circuit.
  - Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
CHECK THE BCM FOR CORRECT OPERATION
1. Reconnect the BCM C3 harness connector.
2. Connect a 12-volt test light between the (L56) Brake Lamp Switch Output circuit and ground circuit at the CHMSL harness connector.
3. Turn the ignition on.
4. Activate the Stop Lamps.
  Does the test light illuminate with the Stop Lamps activated?
  
  Yes
  - Replace the CHMSL in accordance with the service information.
  - Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .
  No
  - Replace the BCM in accordance with the service information. Refer to REMOVAL .
  - Perform the BODY VERIFICATION TEST. Refer to BODY VERIFICATION TEST .