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

WARNING: This page is about a different car, the 2009 Mercury Grand Marquis and 2009 Ford Crown Victoria. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
  1. B1 CHECK THE OPERATION OF THE STOPLAMPS 
    • Key in ON position.
    • Operate the stoplamps.
    • Do the stoplamps operate correctly? 
    1. YES  : Go to  B2.
    2. NO  : REFER to EXTERIOR LIGHTING article.
  2. B2 CHECK THE SPEED CONTROL DEACTIVATOR SWITCH FOR CORRECT OPERATION 
    • Key in OFF position.
    • Disconnect: PCM C175b
      • Fig 1: Checking Speed Control Deactivator Switch Voltage
      GF0014219Courtesy 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  B6.
    2. NO  : Go to  B3.
  3. B3 CHECK CIRCUIT 1119 (RD) FOR AN OPEN 
    • Disconnect: Speed Control Deactivator Switch C277
      • Fig 2: Checking Circuit For Voltage
      GF0014220Courtesy of FORD MOTOR CO.
    • Measure the voltage between the speed control deactivator switch C277-1, circuit 1119 (RD), harness side and ground.
    • Is the voltage greater than 10 volts? 
    1. YES  : Go to  B4.
    2. NO  : VERIFY the battery junction box (BJB) fuse 14 (20A) is OK. If OK, REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
  4. B4 CHECK CIRCUIT 636 (OG) FOR A SHORT TO VOLTAGE 
    • Key in ON position.
      • Fig 3: Checking Circuit For Voltage
      GF0004252Courtesy of FORD MOTOR CO.
    • Measure the voltage between the speed control deactivator switch C277-2, 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  B5.
  5. B5 CHECK CIRCUIT 636 (OG) FOR AN OPEN 
    • Key in OFF position.
      • Fig 4: Checking Circuit For Open
      GF0014221Courtesy of FORD MOTOR CO.
    • Measure the resistance between the speed control deactivator switch C277-2, 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.
  6. B6 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 ELECTRONIC ENGINE CONTROLS article.
    2. NO  : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
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