Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Test Procedure
- FD1 CHECK FOR DIAGNOSTIC TROUBLE CODES (DTC)
Are DTCs P0504, P0572, P0573, P0703, P1572, or P1703 present?
Yes No For KOEO or continuous memory DTCs P0504, P0572, P0573, P0703, P1703 and continuous memory DTC P1572, GO to FD3.
For KOER DTCs P0703, or P1703, GO to FD2.For all others, GO to DTC LIST . - FD2 KOER DTCS P0703 AND P1703: VERIFY THE BRAKE PEDAL WAS APPLIED
Was the brake pedal applied and released during the KOER self-test?
Yes No GO to FD3. REPEAT the KOER self-test. APPLY and RELEASE the brake pedal during the KOER test.
CLEAR the DTCs. REPEAT the self-test. - FD3 DTCS P0572, P0573, P0703, P1572 AND P1703: CHECK THE OPERATION OF THE STOPLAMPS
- Ignition ON, engine OFF.
- Apply and release the brake pedal and check the stop lamp operation.
Do the stoplamps operate correctly?
Yes No For Crown Victoria,
Flex,
Grand Marquis,
MKS,
Sable,
Taurus,
Taurus X, and
Town Car, GO to FD4.
For all others, GO to FD5.REFER to the appropriate Exterior Lighting article , to DIAGNOSE the inoperative stoplamps. REPAIR as necessary. CLEAR the DTCs. REPEAT the self-test. - FD4 CHECK THE BRAKE SWITCH OPERATION
- Ignition ON, engine OFF.
- Access the PCM and monitor the BOO PID.
- Apply and release the brake pedal while monitoring the brake position PID.
Does the PID cycle ON and OFF?
Yes No GO to FD6. REFER to the appropriate Module Communications Network article , to DIAGNOSE the powertrain control module (PCM) not responding to the scan tool. REPAIR as necessary. CLEAR the DTCs. REPEAT the self-test. - FD5 CHECK FOR BPP CIRCUIT CYCLING
- Ignition OFF.
- PCM connector disconnected.
- Ignition ON, engine OFF.
- Apply and release the brake pedal while monitoring the voltage.
- Measure the voltage between:
(+) PCM Connector, Harness Side (-) BPP Ground
Is voltage less than 1 volt with the brake pedal released and greater than 10 volts with the brake pedal fully applied?
Yes No For Ranger, GO to FD7.
For all others, GO to FD6.REPAIR the open circuit. CLEAR the DTCs. REPEAT the self-test. - FD6 CHECK FOR BRAKE PRESSURE SWITCH CIRCUIT CYCLING
- Ignition OFF.
- PCM connector disconnected.
- Ignition ON, engine OFF.
- Apply and release the brake pedal while monitoring the voltage.
- Measure the voltage between:
(+) PCM Connector, Harness Side (-) BPS Ground
Is voltage greater than 10 volts with the brake pedal released and less than 1 volt with the brake pedal fully applied?
Yes No GO to FD7. REFER to the appropriate Speed Control article . CARRY OUT the diagnostic steps for DTC P1703 to continue diagnose. - FD7 CHECK FOR CORRECT PCM OPERATION
- Disconnect all the PCM connectors.
- Visually inspect for:
- pushed out pins
- corrosion
- Connect all the PCM connectors and make sure they seat correctly.
- Carry out the PCM self-test and verify the concern is still present.
Is the concern still present?
Yes No INSTALL a new PCM. REFER to FLASH ELECTRICALLY ERASABLE PROGRAMMABLE READ ONLY MEMORY (EEPROM) , Programming the VID Block for a Replacement PCM. The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.