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.

ACTIVE DTC
1. Ignition on, engine not running.
2. With a scan tool, select View DTCs.
  NOTE:
  It may be necessary to drive the vehicle to meet the conditions to set this DTC, try to repeat the conditions in which the fault originally set by reviewing the Freeze Frame data.
  
  Is the DTC Active at this time?
  
  Yes
  - Go To 2
  No
  - Perform the INTERMITTENT CONDITION diagnostic procedure. Refer to INTERMITTENT CONDITION .
STOP LAMP SWITCH
1. Turn the ignition off.
2. Disconnect the Stop Lamp Switch harness connector.
3. Measure the resistance between terminal 1 and terminal 4 at the Stop Lamp Switch.
4. Apply and release the Stop Lamp Switch while monitoring the Ohmmeter.
  Does the resistance change from below 5.0 Ohms to an open circuit for the measurement taken?
  
  Yes
  - Go To 3
  No
  - Verify that there is good pin to terminal contact in the Switch and Powertrain Control Module harness connectors. If OK, replace the Stop Lamp Switch. Refer to SWITCH, STOP LAMP, REMOVAL .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 16V .
CHECK THE (L56) BRAKE LAMP SWITCH OUTPUT CIRCUIT FOR AN OPEN
1. Disconnect the PCM C1 harness connector.
2. Measure the resistance of the (L56) Brake Lamp Switch Output circuit between the Stop Lamp Switch harness connector and the appropriate terminal of the PCM C1 harness connector.
  Is the resistance below 5.0 Ohms?
  
  Yes
  - Go To 4
  No
  - Repair the (L56) Brake Lamp Switch Output circuit for an open.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 16V .
CHECK THE (L56) BRAKE LAMP SWITCH OUTPUT CIRCUIT FOR A SHORT TO GROUND
1. Disconnect the Center High Mount Stop Lamp harness connector.
2. Measure the resistance between ground and the (L56) Brake Lamp Switch Output circuit at the Stop Lamp Switch harness connector.
  Is the resistance above 10k Ohms?
  
  Yes
  - Go To 5
  No
  - Repair the (L56) Brake Lamp Switch Output circuit for a short to ground.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 16V .
CHECK THE (A103) STOP LAMP SWITCH BATTERY FEED CIRCUIT FOR AN OPEN
1. Remove Fuse 51 (10A) from the Power Distribution Center (PDC).
2. Measure the resistance of the (A103) Stop Lamp Switch Battery Feed circuit from the PDC to the Stop Lamp Switch harness connector.
  Is the resistance below 5.0 Ohms?
  
  Yes
  - Go To 6
  No
  - Repair the open in the (A103) Stop Lamp Switch Battery Feed circuit.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 16V .
POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Stop Lamp Switch and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the Switch and Powertrain Control Module harness connectors.
4. Perform any Technical Service Bulletins that may apply.
  Were there any problems found?
  
  Yes
  - Repair as necessary.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 16V .
  No
  - Replace and program the Powertrain Control Module in accordance with the Service Information. Refer to MODULE, POWERTRAIN CONTROL, REMOVAL and PROGRAM THE PCM (POWERTRAIN CONTROL MODULE) .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 16V .