Pinpoint Test A: No Communication With The Navigation System Module

WARNING: This page is about a different car, the 2005 Lincoln Town Car. However, it is still accessible from the selected car via links, so may be relevant.

A1 CHECK CIRCUITS 1772 (VT) AND 1499 (PK/LG) FOR VOLTAGE
- Key in OFF position.
- Disconnect: Navigation System Module C4209.
- Key in ON position.
- Measure the voltage between the navigation system module C4209 pin 1, circuit 1772 (VT), harness side and ground; and between the navigation system module C4209 pin 2, circuit 1499 (PK/LG), harness side and ground.
  
  Fig 1: Measuring Voltage Between Navigation System Module C4209 Pin 1, Circuit 1772 (VT), Harness Side And Ground; And Between Navigation System Module C4209 Pin 2, Circuit 1499 (PK/LG), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- Are the voltages greater than 10 volts?
- Yes : GO to A2.
- No : REPAIR the circuit in question. REPEAT the self-test.
A2 CHECK CIRCUIT 694 (BK/LG) FOR AN OPEN
- Key in OFF position.
- Measure the resistance between the navigation system module C4209 pin 13, circuit 694 (BK/LG), harness side and ground.
  
  Fig 2: Measuring Resistance Between Navigation System Module C4209 Pin 13, Circuit 694 (BK/LG), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
- Yes : REFER to MODULE COMMUNICATIONS NETWORK to continue diagnosis of the communication network.
- No : REPAIR the circuit. REPEAT the self-test.