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.

Refer to SWITCH, STOP LAMP for further information.

ACTIVE DTC
NOTE:
Make sure the Stop Lamp Switch is adjusted properly before continuing.
1. Ignition on, engine not running.
2. With the scan tool, select View DTCs.
3. It may be necessary to press and release the Brake Pedal to get the fault to become Active.
  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 OPERATION
1. Turn the ignition off.
2. Disconnect the Stop Lamp Switch harness connector.
3. Measure the resistance between the Fused B+ circuit terminal and the Brake Lamp Switch Output circuit terminal in 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 open circuit when pressing and releasing the brake pedal switch?
  
  Yes
  - Go To 3
  No
  - Replace the Stop Lamp Switch.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 16V Turbo .
STOP LAMP SWITCH OPERATION
1. Measure the resistance between the Fused Ignition Run-Start Control Output circuit terminal and the Brake Signal 2 circuit terminal in the Stop Lamp Switch.
2. Apply and release the Stop Lamp Switch while monitoring the ohmmeter.
  Does the resistance change from below 5.0 Ohms to open circuit when pressing and releasing the Stop Lamp switch?
  
  Yes
  - Go To 4
  No
  - Replace the Stop Lamp Switch.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 16V Turbo .
CHECK THE (L56) BRAKE LAMP SWITCH OUTPUT CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Disconnect the PCM C1 harness connector.
2. Measure the resistance of the (L56) Brake Lamp Switch Output circuit from the Stop Lamp Switch harness connector to the PCM C1 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 POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 16V Turbo .
CHECK THE (B134) BRAKE SIGNAL 2 CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Disconnect the BCM C1 harness connector.
2. Measure the resistance of the (B134) Brake Signal 2 circuit from the Stop Lamp Switch harness connector to the BCM C1 harness connector.
  Is the resistance below 5.0 Ohms?
  
  Yes
  - Go To 6
  No
  - Repair the open in the (B134) Brake Signal 2 circuit.
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 16V Turbo .
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 Turbo .
  No
  - Replace and program the Powertrain Control Module in accordance with the Service Information. Refer to MODULE, POWERTRAIN CONTROL, REMOVAL .
  - Perform the POWERTRAIN VERIFICATION TEST. Refer to POWERTRAIN VERIFICATION TEST, 16V Turbo .