Pinpoint Test O: The Navigation System Is Inoperative

WARNING: This page is about a different car, the 2006 Mercury Mariner and 2006 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.

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

O1 CHECK CIRCUIT 137 (YE/BK) FOR VOLTAGE
- Key in OFF position.
- Disconnect: Audio Unit C229a.
- Key in ON position.
- Measure the voltage between the audio unit C229a-3, circuit 137 (YE/BK), harness side and ground.
  
  Fig 1: Checking Circuit 137 (YE/BK) For Voltage
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
Yes : GO to O2.

No : VERIFY the smart junction box (SJB) fuse 12 (5A) is OK. If OK, REPAIR the circuit. TEST the system for normal operation.
O2 CHECK CIRCUIT 1786 (BN/PK) FOR A SHORT TO VOLTAGE
- Key in OFF position.
- Disconnect: Audio Unit C229e.
- Key in ON position.
- Measure the voltage between the audio unit C229e-7, circuit 1786 (BN/PK), harness side and ground.
  
  Fig 2: Checking Circuit 1786 (BN/PK) For A Short To Voltage
  Courtesy of FORD MOTOR CO.
- Is any voltage present?
Yes : REPAIR the circuit. TEST the system for normal operation.

No : GO to O3.
O3 CHECK CIRCUIT 956 (OG/LG) FOR VOLTAGE
- Key in OFF position.
- Measure the voltage between the audio unit C229a-1, circuit 956 (OG/LG), harness side and ground.
  
  Fig 3: Checking Circuit 956 (OG/LG) For Voltage
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
Yes : GO to O4.

No : VERIFY the SJB fuse 7 (10A) is OK. If OK, REPAIR the circuit. TEST the system for normal operation.
O4 CHECK CIRCUIT 694 (BK/LG) FOR AN OPEN
- Measure the resistance between the audio unit C229a-6, circuit 694 (BK/LG), harness side and ground.
  
  Fig 4: Checking Circuit 694 (BK/LG) For An Open
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
Yes : GO to O5.

No : REPAIR the circuit. TEST the system for normal operation.
O5 CHECK FOR CORRECT AUDIO UNIT OPERATION
- Disconnect all the audio unit connectors.
- Check for:
  - corrosion
  - pushed-out pins
- Connect all the audio unit connectors and make sure they seat correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
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.

No : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.