What causes fault code P0231?

• Most likely: Defective fuel pump relay (burnt contacts) • Likely: Blown fuel pump fuse (often caused by high pump current draw) • Possible: Damaged wiring or corrosion in connectors between the relay and ECM • Rare: Faulty fuel pump (internal short or open circuit) • Rare: Internal ECM failure

Powertrain (Engine & Gearbox)Standard EOBD

P0231 - Fuel Pump Secondary Circuit Low

Q: What are the symptoms of fault code P0231?

• Check engine light (MIL) illuminated • Engine will not start • Engine stalls while driving • Hard start conditions • Engine hesitates or stumbles under load

Q: How do you fix fault code P0231?

STEP 1: Check the fuel pump fuse and relay. Replace if blown or showing signs of overheating. STEP 2: Measure voltage at the relay output using a multimeter. Should show battery voltage (~12.6V) when commanded. If voltage is low (<10V) at the output but high at the input, replace relay. STEP 3: Inspect wiring for chafing or corrosion, especially at the relay block connectors. Perform a continuity test (resistance <0.5 Ohm) on the feedback wire to the ECM. STEP 4: Use a scan tool to perform a component test of the fuel pump. Measure the fuel pump current draw; if it exceeds 10-15A (check specs), the pump is likely failing and should be replaced.

Last updated:1 February 2026

Related:Fuel Pump Relay, Fuel Pump fuse, Fuel Pump (Lift Pump), Wiring harness, ECM (Engine Control Module)

System

Powertrain (Engine & Gearbox)

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Technical Description

P0231 is a diagnostic trouble code (DTC) for 'Fuel Pump Secondary Circuit Low'. This occurs when the Engine Control Module (ECM) detects a lower-than-expected voltage (typically less than 2-5V) on the feedback circuit that monitors the fuel pump supply voltage. When the ECM commands the fuel pump relay to bridge the power to the pump, it monitors the circuit to confirm voltage is present. If the relay is commanded 'ON' but the feedback signal remains low, the ECM concludes there is a circuit malfunction, potentially leading to fuel starvation or a complete no-start condition.

Possible Causes

Defective fuel pump relay (burnt contacts)

Blown fuel pump fuse (often caused by high pump current draw)

Damaged wiring or corrosion in connectors between the relay and ECM

Faulty fuel pump (internal short or open circuit)

Internal ECM failure

Symptoms

Check engine light (MIL) illuminated

Engine will not start

Engine stalls while driving

Hard start conditions

Engine hesitates or stumbles under load

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P0231 - Fuel Pump Secondary Circuit Low

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P0231 - Fuel Pump Secondary Circuit Low

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