Pinpoint Test S: Loud Popping Sound When Cycling The Ignition Switch

WARNING: This page is about a different car, the 2010 Mercury Milan, 2010 Lincoln MKZ, and 2010 Ford Fusion. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.

S1 CHECK THE START INPUT CIRCUIT VOLTAGE
- Ignition OFF.
- Disconnect: ACM C240a.
- Disconnect: Starter Relay.
- Hold the key in the START position.
- Measure the voltage between the ACM C240a-15, circuit CBP28 (GY/VT), harness side and ground.
  
  Fig 1: Measuring Voltage Between ACM C240A-15 And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
- Yes : INSTALL a new ACM . REFER to AUDIO CONTROL MODULE (ACM) - FUSION, MILAN or AUDIO CONTROL MODULE (ACM) - MKZ . TEST the system for normal operation.
- No : VERIFY the Smart Junction Box (SJB) fuse 28 (5A) is OK. If OK, REPAIR the circuit. TEST the system for normal operation. If not OK, REFER to the appropriate SYSTEM WIRING DIAGRAMS article to identify the possible causes of the circuit short.