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

WARNING: This page is about a different car, the 2007 Lincoln Mark LT and 2007 Ford Pickup. However, it is still accessible from the selected car via links, so may be relevant.

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

E1 CHECK CIRCUIT 1000 (RD/BK) OR 325 (DB/OG) FOR VOLTAGE
- Key in OFF position.
- Disconnect: Audio Unit C290a
- Disconnect: Starter Relay C2163
- Key in START position.
- Measure the voltage between the audio unit C290a-15, circuit 1000 (RD/BK) or 325 (DB/OG), harness side and ground.
  
  Fig 1: Checking Circuit 1000 (RD/BK) Or 325 (DB/OG) For Voltage
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
1. YES : If the vehicle is equipped with a subwoofer, go to E2 .
  For all others, SEND the audio unit to an authorized audio system repair facility. TEST the system for normal operation after the repair.
2. NO : VERIFY the central junction box (CJB) fuse 7 (5A) is OK. If OK, REPAIR the circuit. TEST the system for normal operation.
E2 ISOLATE THE SUBWOOFER
- Key in OFF position.
- Connect: Audio Unit C290a
- Disconnect: Subwoofer C3020
- Cycle the key through all of the ignition switch positions.
- Is a loud popping sound present?
1. YES : REMOVE the audio unit and SEND it to an authorized audio system repair facility. REFER to Audio Unit in this article. TEST the system for normal operation after the repair.
2. NO : INSTALL a new subwoofer. REFER to Speaker Enclosure in this article. TEST the system for normal operation.