Pinpoint Test B: DTC P1572 Or DTC 1703 - Brake On/Off Circuit Failure

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

B1 CHECK THE OPERATION OF THE STOPLAMPS
- Apply and release the brake pedal while observing the stoplamps.
- Do the stoplamps operate correctly?
- Yes : GO to B2.
- No : REFER to EXTERIOR LIGHTING to continue diagnosis of the stoplamps.
B2 CHECK THE CIRCUIT 511 (LG) FOR AN OPEN
- Key in OFF position.
- Disconnect: Powertrain Control Module (PCM) C175b.
- While applying the brake pedal, measure the voltage between the PCM C175b-46, circuit 511 (LG), harness side and ground.
  
  Fig 1: Measuring Voltage Between PCM C175b-46, Circuit 511 (LG), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
- Yes : GO to B3.
- No : REPAIR the circuit. CLEAR the DTCs. REPEAT the self test.
B3 CHECK THE SPEED CONTROL DEACTIVATOR SWITCH FOR CORRECT OPERATION
- Key in ON position.
- While firmly applying and releasing the brake pedal, measure the voltage between the PCM C175b-47, circuit 307 (BK/YE), harness side and ground.
  
  Fig 2: Measuring Voltage Between PCM C175b-47, Circuit 307 (BK/YE), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts with the brake pedal released and 0 volts with the brake pedal firmly applied?
- Yes : GO to B7.
- No : GO to B4.
B4 CHECK CIRCUIT 295 (LB/PK) FOR AN OPEN
- Key in OFF position.
- Disconnect: Speed Control Deactivator Switch C277.
- Key in ON position.
- Measure the voltage between the speed control deactivator switch C277-2, circuit 295 (LB/PK), harness side and ground.
  
  Fig 3: Measuring Voltage Between Speed Control Deactivator Switch C277-2, Circuit 295 (LB/PK), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
- Yes : GO to B5.
- No : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
B5 CHECK CIRCUIT 307 (BK/YE) FOR A SHORT TO VOLTAGE
- Measure the voltage between the speed control deactivator switch C277-1, circuit 307 (BK/YE), harness side and ground.
  
  Fig 4: Measuring Voltage Between Speed Control Deactivator Switch C277-1, Circuit 307 (BK/YE), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- Is any voltage present?
- Yes : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
- No : GO to B6.
B6 CHECK CIRCUIT 307 (BK/YE) FOR AN OPEN
- Key in OFF position.
- Measure the resistance between the PCM C277-1, circuit 307 (BK/YE), harness side and the speed control deactivator switch C277-1, circuit 307 (BK/YE), harness side.
  
  Fig 5: Checking Circuit 307 (BK/YE) For An Open
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
- Yes : INSTALL a new speed control deactivator switch. REFER to SPEED CONTROL DEACTIVATOR SWITCH . CLEAR the DTCs. REPEAT the self-test.
- No : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
B7 CHECK FOR CORRECT PCM OPERATION
- Disconnect all the PCM connectors.
- Check for:
  - Corrosion
  - Pushed-out pins
- Connect all the PCM connectors and make sure they seat correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
- Yes : INSTALL a new PCM. REFER to ELECTRONIC ENGINE CONTROLS . 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. CLEAR the DTCs. REPEAT the self-test.