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
- AI1 CHECK FOR DTCS
Are DTCs P0504, P0572, P0573 or P1703 present?
Yes No For KOER DTC P1703, GO to AI2.
For all others, GO to AI3.Unable to duplicate the condition. CHECK for a loose connection, and damaged or corroded terminals. WIGGLE the harness attempting to recreate the concern. REPAIR as necessary.
RETURN to SYMPTOM CHARTS for further direction. - AI2 VERIFY THE BRAKE PEDAL WAS APPLIED
Was the brake pedal applied and released during the KOER self-test?
Yes No GO to AI3. REPEAT the KOER self-test. APPLY and RELEASE the brake pedal during the KOER test.
Clear the PCM DTCs. REPEAT the self-test. - AI3 CHECK THE OPERATION OF THE STOPLAMPS
- Ignition ON, engine OFF.
- Apply and release the brake pedal and check the stoplamp operation.
Do the stoplamps operate correctly?
Yes No GO to AI4. REFER to the Exterior Lighting article, to diagnose all the stoplamps are inoperative.
Clear the PCM DTCs. REPEAT the self-test. - AI4 CHECK THE BRAKE SWITCH OPERATION
- Access the PCM and monitor the BOO1 (MODE) PID.
- Apply and release the brake pedal while monitoring the brake position PID.
Does the BOO1 PID state change when the brake pedal is fully applied and released?
Yes No For F-650/750 with air brakes, the system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. No fault found.
Clear the PCM DTCs. REPEAT the self-test.
For all others, GO to AI6.GO to AI5. - AI5 CHECK FOR BPP CIRCUIT CYCLING
- Ignition OFF.
- PCM-B connector disconnected.
- Ignition ON, engine OFF.
- Fully apply and release the brake pedal while measuring the voltage.
- Measure the voltage between:
(+) PCM-B Connector, Harness Side (-) BPP Ground
Is voltage less than 1 volt with the brake pedal released and greater than 10.5 volts with the brake pedal fully applied?
Yes No For F-650/750 with air brakes, The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. No fault found.
Clear the PCM DTCs. REPEAT the self-test.
For all others, GO to AI6.REPAIR the open circuit. Clear the PCM DTCs. REPEAT the self-test. - AI6 CHECK FOR BPS CIRCUIT CYCLING
- Ignition OFF.
- PCM-B connector disconnected.
- Fully apply and release the brake pedal while measuring the resistance.
- Measure the resistance between:
(+) PCM-B Connector, Harness Side (-) BPS Ground
Is the resistance less than 5 ohms with brake pedal released and greater than 10, 000 ohms with the brake pedal pressed?
Yes No GO to AI11. GO to AI7. - AI7 CHECK THE BPP SWITCH FOR CORRECT OPERATION
- Ignition OFF.
- BPP Switch connector disconnected.
- Fully apply and release the brake pedal while measuring the resistance.
- Measure the resistance between:
(+) BPP Switch Connector, Component Side (-) BPP Switch Connector, Component Side BPS - Pin 2 GND - Pin 3
Is the resistance less than 5 ohms with the brake pedal released and greater than 10, 000 ohms with the brake pedal pressed?
Yes No GO to AI8. INSTALL a new BPP switch. Clear the PCM DTCs. REPEAT the self-test. - AI8 CHECK THE BPS AND GND CIRCUITS FOR AN OPEN
- Measure the resistance between:
(+) PCM-B Connector, Harness Side (-) BPP Switch Connector, Harness Side BPS BPS - Pin 2 - Measure the resistance between:
(+) BPP Switch Connector, Harness Side (-) GND - Pin 3 Ground
Are the resistances less than 5 ohms?
Yes No GO to AI9. REPAIR the open circuit. Clear the PCM DTCs. REPEAT the self-test. - Measure the resistance between:
- AI9 CHECK THE BPS CIRCUIT FOR A SHORT TO GROUND
Is the resistance greater than 10K ohms?
Yes No GO to AI10. REPAIR the short circuit. Clear the PCM DTCs. REPEAT the self-test. - AI10 CHECK THE BPS CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition ON, engine OFF.
- Measure the voltage between:
(+) PCM-B Connector, Harness Side (-) BPS Ground
Is any voltage present?
Yes No REPAIR the short circuit. Clear the PCM DTCs. REPEAT the self-test. GO to AI11. - AI11 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.
- 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) . The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
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.