Pinpoint Test Ab: Loud Popping Sound When Cycling The Ignition

WARNING: This page is about a different car, the 2010 Lincoln MKX and 2010 Ford Edge. 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.

AB1 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, Circuit CBP28 (GY/VT), Harness Side 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) . 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 SYSTEM WIRING DIAGRAMS for Edge or SYSTEM WIRING DIAGRAMS for MKX to identify the possible causes of the circuit short.