Pinpoint Test C: All The Locks Operate From One Switch Only

WARNING: This page is about a different car, the 2006 Ford F550 Super Duty, 2006 Ford F450 Super Duty, and 2006 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

C1 CHECK THE VOLTAGE TO THE INOPERATIVE DOOR LOCK CONTROL SWITCH
- Disconnect: Passenger Door Lock Control Switch C605.
- Disconnect: Driver Door Lock Control Switch C505.
- Measure the voltage between the inoperative door lock control switch C605-4 (passenger), or C505-4 (driver), circuit 116 (RD/BK), and ground.
  
  Fig 1: Checking Voltage To Inoperative Door Lock Control Switch
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
Yes : GO to

No : REPAIR the circuit. TEST the system for normal operation.
C2 CHECK THE CIRCUITRY RESISTANCE
- Measure the resistance between the driver door lock control switch C505-7, circuit 119 (PK/YE), harness side and ground.
  
  Fig 2: Checking Circuitry Resistance (1 Of 2)
  Courtesy of FORD MOTOR CO.
- Measure the resistance between the driver door lock control switch C505-3, circuit 120 (PK/LG), harness side and ground.
  
  Fig 3: Checking Circuitry Resistance (2 Of 2)
  Courtesy of FORD MOTOR CO.
- Are the resistances greater than 10,000 ohms?
Yes : INSTALL a new door lock control switch. REFER to DOOR LOCK CONTROL SWITCH . TEST the system for normal operation.

No : REPAIR the circuit(s) in question. TEST the system for normal operation.