Pinpoint Test B: DTC P1703 Or DTC P1572 - Brake On/Off Circuit Failure

Refer to appropriate SYSTEM WIRING DIAGRAMS article, Speed Control for schematic and connector information.

Refer to appropriate SYSTEM WIRING DIAGRAMS article, Turn Signal/Stop/Hazard Lamps for schematic and connector information.

Normal Operation 

Fused battery voltage is sent from the central junction box (CJB) fuse 14 (20A) through circuit 1119 (RD) to the brake pedal position switch. When the brake pedal is depressed, voltage is supplied to the CJB fuse 28 (7.5A) through circuit 511(LG) and then to the ABS module through circuit 1651 (WH/RD). The ABS module sends the brake pedal position to the PCM over the high speed controller area network (HS-CAN) bus lines interrupting the speed control. The speed control deactivator switch interrupts the power signal to the PCM through circuit 636 (OG) when the brake pedal is applied firmly. This is a redundant signal to the PCM.

• DTC P1572 (Brake Pedal Switch Circuit) - sets when the PCM does not sense the proper sequence of the brake pedal input signal from both the stoplamp and deactivator switches when the brake pedal is pressed and released.
• DTC P1703 (Brake Switch Out of Self-Test Range) - sets when there is an open or short in the deactivator switch circuits or when there is an open or short in the stoplamp circuits.

This pinpoint test is intended to diagnose the following:

• Wiring, terminals or connectors
• Speed control deactivator switch
• PCM

PINPOINT TEST B: DTC P1703 OR DTC P1572 - BRAKE ON/OFF CIRCUIT FAILURE 

1. B1 CHECK THE OPERATION OF THE SHIFT INTERLOCK SYSTEM 
   • Key in ON position.
   • Operate the shift interlock system.
   • Does the shift interlock system operate correctly? 
   1. YES  : Go to  B2.
   2. NO  : REFER to DIAGNOSTIC TESTS article.
2. B2 CHECK STOPLAMP SWITCH INPUT TO THE ABS MODULE 
   • Enter the following diagnostic mode on the diagnostic tool: ABS DataLogger
   • Monitor the ABS BOO_ABS (brake pedal position switch) PID while applying and releasing the brake pedal.
   • Do the PIDs agree with the stoplamp switch position? 
   1. YES  : Go to  B3.
   2. NO  : REFER to DIAGNOSTIC TESTS article.
3. B3 CHECK THE SPEED CONTROL DEACTIVATOR SWITCH FOR CORRECT OPERATION 
   • Key in OFF position.
   • Disconnect: PCM C175b
   Fig 1: Checking Speed Control Deactivator Switch Voltage
   Courtesy of FORD MOTOR CO.
   • While firmly applying and releasing the brake pedal, measure the voltage between the PCM C175b-9, circuit 636 (OG), harness side and ground.
   • Is the voltage greater than 10 volts with the brake pedal released and 0 volts with the brake pedal firmly applied? 
   1. YES  : Go to  B7.
   2. NO  : Go to  B4.
4. B4 CHECK CIRCUIT 1119 (RD) FOR AN OPEN 
   • Disconnect: Speed Control Deactivator Switch C277
   Fig 2: Checking Circuit For Voltage
   Courtesy of FORD MOTOR CO.
   • Measure the voltage between the speed control deactivator switch C277-2, circuit 1119 (RD), harness side and ground.
   • Is the voltage greater than 10 volts? 
   1. YES  : Go to  B5.
   2. NO  : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
5. B5 CHECK CIRCUIT 636 (OG) FOR A SHORT TO VOLTAGE 
   • Key in ON position.
   Fig 3: Checking Circuit For Voltage
   Courtesy of FORD MOTOR CO.
   • Measure the voltage between the speed control deactivator switch C277-1, circuit 636 (OG), harness side and ground.
   • Is any voltage present? 
   1. YES  : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
   2. NO  : Go to  B6.
6. B6 CHECK CIRCUIT 636 (OG) FOR AN OPEN 
   • Key in OFF position.
   Fig 4: Checking Circuit For Open
   Courtesy of FORD MOTOR CO.
   • Measure the resistance between the speed control deactivator switch C277-1, circuit 636 (OG), harness side and the PCM C175b-9, circuit 636 (OG), harness side.
   • Is the resistance less than 5 ohms? 
   1. YES  : INSTALL a new speed control deactivator switch. REFER to Speed Control Deactivator Switch . CLEAR the DTCs. REPEAT the self-test.
   2. NO  : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
7. B7 CHECK FOR CORRECT PCM OPERATION 
   • Disconnect all the PCM connectors.
   • Check for:
     • corrosion
     • damaged pins
     • pushed-out pins
   • Connect all the PCM connectors and make sure they are seated correctly.
   • Operate the system and verify the concern is still present.
   • Is the concern still present? 
   1. YES  : INSTALL a new PCM. REFER to REMOVAL & INSTALLATION article. TEST the system for normal operation.
   2. 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.