Pinpoint Test A: The Audio Unit Is Inoperative

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.

NOTE: Verify the accessory delay operates correctly before performing this pinpoint test.

A1 CHECK CIRCUITS 797 (LG/VT) AND 54 (LG/YE) OR 489 (PK/BK) FOR VOLTAGE
- Key in OFF position.
- Disconnect: Audio Unit C290a
- Key in ON position.
- Measure the voltage between the audio unit C290a-1, circuit 797 (LG/VT), harness side and ground; and between the audio unit C290a-2, circuit 54 (LG/YE), or circuit 489 (PK/BK), harness side and ground.
  
  Fig 1: Checking Circuits 797 (LG/VT) And 54 (LG/YE) Or 489 (PK/BK) For Voltage
  Courtesy of FORD MOTOR CO.
- Are the voltages greater than 10 volts?
1. YES : Go to A2.
2. NO : VERIFY the central junction box (CJB) fuse 1 (10A), fuse 22 (10A), or fuse 31 (20A) is OK. If OK, REPAIR the circuit in question. TEST the system for normal operation.
A2 CHECK CIRCUITS 57 (BK) AND 694 (BK/LG) FOR AN OPEN
- Key in OFF position.
- Measure the resistance between the audio unit C290a-13, circuit 694 (BK/LG), harness side and ground; and between the audio unit C290a-4, circuit 57 (BK), harness side and ground.
  
  Fig 2: Checking Circuits 57 (BK) And 694 (BK/LG) For Open
  Courtesy of FORD MOTOR CO.
- Are the resistances less than 5 ohms?
1. YES : SEND the audio unit to an authorized audio system repair facility. TEST the system for normal operation after the repair.
2. NO : REPAIR the circuit in question. TEST the system for normal operation.