Diagnostic Test

WARNING: This page is about a different car, the 2015 Fiat 500. However, it is still accessible from the selected car via links, so may be relevant.

CHECK FOR AN INTERMITTENT CONDITION
1. Turn the ignition on.
2. With the scan tool, clear all DTCs.
3. Activate the Stop Lamps off and on.
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 CONTROL MODULE (BCM) - BODY VERIFICATION TEST - 500 - EXCEPT ELECTRIC .
ATTEMPT TO SET DTC: B16B7-13-CENTER HIGH MOUNTED STOP LIGHT - CIRCUIT OPEN
1. Turn the ignition off.
2. Disconnect the Center High Mounted Stop Lamp (CHMSL) harness connector.
3. Turn the ignition on.
4. Activate the Stop Lamps on and off several times.
5. With the scan tool, read DTCs.
  Does the scan tool display DTC: B16B7-13-CENTER HIGH MOUNTED STOP LIGHT - CIRCUIT OPEN?
  
  Yes
  - Replace the CHMSL Bulb or Lamp causing the short to ground condition in accordance with the Service Information.
  - Perform the BODY VERIFICATION TEST. Refer to BODY CONTROL MODULE (BCM) - BODY VERIFICATION TEST - 500 - EXCEPT ELECTRIC .
  No
  - Go To 3
CHECK THE (L56) BRAKE LAMP SWITCH OUTPUT CIRCUIT FOR A SHORT TO GROUND
1. Turn the ignition off.
2. Disconnect the BCM C3 harness connector.
3. Measure the resistance of the (L56) Brake Lamp Switch Output circuit between ground and the CHMSL harness connector.
  Is the resistance above 10k Ohms?
  
  Yes
  - Replace the BCM in accordance with the Service Information. Refer to MODULE, BODY CONTROL, REMOVAL .
  - Perform the BODY VERIFICATION TEST. Refer to BODY CONTROL MODULE (BCM) - BODY VERIFICATION TEST - 500 - EXCEPT ELECTRIC .
  No
  - Repair the short to ground in the (L56) Brake Lamp Switch Output circuit.
  - Perform the BODY VERIFICATION TEST. Refer to BODY CONTROL MODULE (BCM) - BODY VERIFICATION TEST - 500 - EXCEPT ELECTRIC .