Pinpoint Test A: No Communication With The Vehicle Security Module

WARNING: This page is about a different car, the 2005 Ford RV Cutaway, 2005 Ford Econoline, 2005 Ford E450 Super Duty, and 2005 Ford Cutaway. However, it is still accessible from the selected car via links, so may be relevant.

A1 CHECK THE VOLTAGE TO THE VEHICLE SECURITY MODULE
- Key in OFF position.
- Disconnect: Vehicle Security Module C203a.
- Disconnect: Vehicle Security Module C203b.
- Key in ON position.
- Measure the voltage between the vehicle security module C203a-12, circuit 517 (BK/WH), harness side and ground; and between the vehicle security module C203b-25, circuit 640 (RD/YE), harness side and ground.
  
  Fig 1: Measuring Voltage Between Vehicle Security Module Circuit 517 And Ground
  Courtesy of FORD MOTOR CO.
- Are the voltages greater than 10 volts?
- Yes : GO to A2.
- No : REPAIR the circuit(s) in question. CLEAR the DTCs. REPEAT the self-test.
A2 CHECK THE GROUND CIRCUITS FOR AN OPEN
- Key in OFF position.
- Measure the resistance between the vehicle security module C203a-13, circuit 1205 (BK), harness side and ground; and between the vehicle security module C203b-14, circuit 57 (BK), harness side and ground.
  
  Fig 2: Measuring Resistance Between Vehicle Security Module Circuit 1205 And Ground
  Courtesy of FORD MOTOR CO.
- Are the resistances less than 5 ohms?
- Yes : REFER to MODULE COMMUNICATIONS NETWORK to continue communication diagnostics.
- No : REPAIR the circuit(s) in question. CLEAR the DTCs. REPEAT the self-test.