Pinpoint Test A: No Communication With The Vehicle Security Module

WARNING: This page is about a different car, the 2004 Ford Explorer Sport Trac. However, it is still accessible from the selected car via links, so may be relevant.

A1 CHECK THE VEHICLE SECURITY MODULE FOR VOLTAGE

Disconnect: Vehicle Security Module C274a.
Disconnect: Vehicle Security Module C274b.
Key in ON position.
Measure the voltage between the vehicle security module C274b pin 12, circuit 1679 (WH/YE), harness side and ground.

Fig 1: Measuring Voltage Between Vehicle Security Module C274B Pin 12, Circuit 1679 (WH/YE), Harness Side And Ground
Courtesy of FORD MOTOR CO.
Measure the voltage between the vehicle security module C274a pin 25, circuit 640 (RD/YE), harness side and ground.

Fig 2: Measuring Voltage Between Vehicle Security Module C274A Pin 25, Circuit 640 (RD/YE), Harness Side And Ground
Courtesy of FORD MOTOR CO.
Are the voltages greater than 10 volts?

Yes

GO to A2.

REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test.

A2 CHECK THE VEHICLE SECURITY MODULE GROUND CIRCUITS

Key in OFF position.
Measure the resistance between the vehicle security module C274a pin 14, circuit 57 (BK), harness side and ground.

Fig 3: Measuring Resistance Between Vehicle Security Module C274A Pin 14, Circuit 57 (BK), Harness Side And Ground
Courtesy of FORD MOTOR CO.
Measure the resistance between the vehicle security module C274b pin 13, circuit 570 (BK/WH), harness side and ground.

Fig 4: Measuring Resistance Between Vehicle Security Module C274B Pin 13, Circuit 570 (BK/WH), Harness Side And Ground
Courtesy of FORD MOTOR CO.
Are the resistances less than 5 ohms?

Yes

REFER to MODULE COMMUNICATIONS NETWORK to continue communication diagnostics.

REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test.