What causes fault code P025C?

• Most likely: Short to ground in the wiring harness between ECM and FPCM • Likely: Faulty Fuel Pump Control Module (FPCM) • Possible: Defective fuel pump relay or blown fuse supplying the module • Rare: Internal Engine Control Module (ECM) failure

How do you fix fault code P025C?

STEP 1: Check fuses related to the fuel system and FPCM. Inspect the connector at the FPCM (often located under the rear seat or near the fuel tank) for corrosion or backed-out pins. STEP 2: Measure supply voltage to the FPCM; it should match battery voltage (approx. 12.6V). Verify the ground circuit (voltage drop should be < 0.1V). STEP 3: Use an oscilloscope to probe the PWM control signal from the ECM. With ignition on/cranking, a pulse width signal should be present. If the signal wire measures 0V even when disconnected from FPCM, there is a short to ground in the harness. STEP 4: If wiring and power/ground are verified but the module does not respond to ECM commands, replace the Fuel Pump Control Module.

Powertrain (Engine & Gearbox)Standard EOBD

P025C - Fuel Pump Control Module (FPCM) - Circuit Low

Q: What does fault code P025C mean?

P025C is stored when the Engine Control Module (ECM) detects an abnormally low voltage state in the Fuel Pump Control Module (FPCM) control circuit. Modern returnless fuel systems use a variable speed pump controlled by the ECM via a PWM (Pulse Width Modulation) signal to the FPCM. If the signal circuit is shorted to ground or the voltage drops below the calibrated threshold (typically less than 0.5V when high activity is expected), the ECM monitors this as a circuit low condition. This interferes with the fuel delivery strategy and rail pressure management.

Q: What are the symptoms of fault code P025C?

• Check engine light illuminated • Engine will not start • Engine hesitation or stalling during drive • Reduced engine power (Limp mode) • Rough idling

Last updated:1 February 2026

Related:Fuel Pump Control Module (FPCM), Engine Control Module (ECM), Fuel Pump, Wiring harness

System

Powertrain (Engine & Gearbox)

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Technical Description

P025C is stored when the Engine Control Module (ECM) detects an abnormally low voltage state in the Fuel Pump Control Module (FPCM) control circuit. Modern returnless fuel systems use a variable speed pump controlled by the ECM via a PWM (Pulse Width Modulation) signal to the FPCM. If the signal circuit is shorted to ground or the voltage drops below the calibrated threshold (typically less than 0.5V when high activity is expected), the ECM monitors this as a circuit low condition. This interferes with the fuel delivery strategy and rail pressure management.

Possible Causes

Short to ground in the wiring harness between ECM and FPCM

Faulty Fuel Pump Control Module (FPCM)

Defective fuel pump relay or blown fuse supplying the module

Internal Engine Control Module (ECM) failure

Symptoms

Check engine light illuminated

Engine will not start

Engine hesitation or stalling during drive

Reduced engine power (Limp mode)

Rough idling

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P025C - Fuel Pump Control Module (FPCM) - Circuit Low

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P025C - Fuel Pump Control Module (FPCM) - Circuit Low

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