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.

TEST FOR INTERMITTENT CONDITION
NOTE:
Check for any TSB(s) related to the condition. If a TSB applies, perform the procedure outlined in the TSB before continuing.
1. Turn the ignition on.
  NOTE:
  Make sure the battery voltage is between 10.0 and 16.0 volts.
2. With the scan tool, read the module status.
  NOTE:
  Check the BCM for any active CAN hardware DTCs, perform DTC before proceeding.
  
  Does the scan tool indicate that the module is active on the bus?
  
  Yes
  - Go To 2
  No
  - The no response condition is not present at this time. Using the wiring diagram/schematic as a guide, inspect the wiring for chafed, pierced, pinched, and partially broken wires and the wiring harness connectors for broken, bent, pushed out, and corroded terminals.
  - Perform the BODY VERIFICATION TEST. Refer to STANDARD PROCEDURE .
CHECK THE FUSED B(+) CIRCUIT FOR AN OPEN OR SHORT
1. Turn the ignition off.
2. Disconnect the Radio harness connector.
3. Using a 12-volt test light connected to ground, check the Fused B(+) circuit.
  Does the test light illuminate brightly?
  
  Yes
  - Go To 3
  No
  - Repair the open or short in the Fused B(+) circuit.
  - Perform the BODY VERIFICATION TEST. Refer to STANDARD PROCEDURE .
CHECK THE GROUND CIRCUIT FOR AN OPEN
1. Using a 12-volt test light connected to 12-volts, check the Ground circuit.
  Does the test light illuminate brightly?
  
  Yes
  - Go To 4
  No
  - Repair the open in the Ground circuit.
  - Perform the BODY VERIFICATION TEST. Refer to STANDARD PROCEDURE .
CHECK THE CAN B BUS CIRCUIT FOR AN OPEN
1. Measure the resistance of the CAN B Bus (-) circuit between the Radio harness connector and the BCM harness connector.
2. Measure the resistance of the CAN B Bus (+) circuit between the Radio harness connector and the BCM harness connector.
  Is resistance below 5.0 Ohms on both circuits?
  
  Yes
  - Replace the Radio in accordance with the Service Information. Refer to RADIO, REMOVAL .
  - Perform the BODY VERIFICATION TEST. Refer to STANDARD PROCEDURE .
  No
  - Repair the open in the CAN B Bus circuit. Inspect the connector for damage.
  - Perform the BODY VERIFICATION TEST. Refer to STANDARD PROCEDURE .