P0231 medium Severity

P0231: Fuel Pump Secondary Circuit Low Voltage

Can cause hard start, stalling, loss of power and no‑start conditions due to inadequate fuel delivery

Overview

P0231 indicates a low voltage condition in the fuel pump secondary circuit (feedback circuit) monitored by the PCM, often involving fuel pump relay, wiring, connectors, fuse or pump issues

Common Symptoms

  • Check engine light illuminated
  • Difficulty starting or no start
  • Engine stalling or rough idle
  • Loss of power or poor acceleration

Most Common Causes

Faulty fuel pump relay high

Relay contacts failing can reduce voltage to fuel pump and trigger code

Damaged or corroded wiring/connectors in secondary circuit high

Opens, shorts to ground, high resistance drops voltage to pump

Blown fuse in fuel pump circuit medium

Fuse failure or high resistance can cause low circuit voltage

Fuel pump internal electrical failure medium

Pump drawing excessive current or internal open causes low voltage feedback

Poor ground connection medium

Bad ground adds resistance, dropping voltage seen by PCM

PCM/ECM circuit driver fault low

Rare but possible if control module monitoring/regulation circuit fails

Diagnostic Steps

  1. Scan and confirm P0231 with an OBD‑II scanner; note any related codes
    Expected: P0231 appears, possibly alongside other fuel system codes
    Interpretation: Confirms code presence and helps contextualize with related faults
  2. Inspect fuel pump fuse and relay; test continuity and swap with known good relay
    Expected: Blown fuse or faulty relay identified
    Interpretation: Blown fuse or failed relay likely cause if circuit cannot energize pump properly
  3. Perform visual inspection of wiring/connectors from relay to fuel pump for damage
    Expected: Frayed, corroded, or loose connections
    Interpretation: Wiring/connection issues likely contributing to low voltage
  4. Measure voltage at fuel pump connector with relay energized
    Expected: Voltage at pump should approach battery voltage
    Interpretation: Low voltage indicates wiring/relay/pump fault; correct circuit issues
  5. Check fuel pump ground integrity
    Expected: Low resistance to chassis ground
    Interpretation: Poor ground increases circuit resistance and can trigger P0231
  6. Test fuel pump internal resistance and operation
    Expected: Pump resistance matches OEM spec; pump runs with correct pressure
    Interpretation: Faulty pump may cause low voltage if internal circuit is compromised
  7. If all external circuit tests are good, verify PCM output driver function
    Expected: PCM driver provides correct control signal voltage
    Interpretation: Abnormal readings suggest PCM fault

Repair Solutions

Replace faulty fuel pump relay easy
Estimated Cost: $30 - $120

Economical fix if relay is the cause

Repair or replace damaged wiring/connectors medium
Estimated Cost: $50 - $400

Cost varies with harness complexity and access

Replace blown fuse and correct root cause easy
Estimated Cost: $5 - $15

Simple fix if fuse failed

Replace fuel pump assembly medium
Estimated Cost: $300 - $800

Necessary if pump internal fault is confirmed

Clean and tighten ground connections easy
Estimated Cost: $10 - $50

Improves circuit return path

PCM/ECM repair or replacement hard
Estimated Cost: $500 - $1500

Only if external circuit verified and module driver is faulty

Common Misdiagnoses

Avoid these common diagnostic mistakes:

  • Assuming a bad fuel pump without verifying circuit integrity first
  • Replacing ECM prematurely without testing wiring, relay, fuse, and connectors

Frequently Asked Questions

Can you explain the meaning of P0231?

When your OBD-II scanner reads P0231, it means: Fuel Pump Secondary Circuit Low Voltage. This code is related to the vehicle's Fuel System.

How serious is the P0231 code?

The P0231 code is considered medium severity. Can cause hard start, stalling, loss of power and no‑start conditions due to inadequate fuel delivery

Symptoms associated with DTC P0231

The most typical signs are: Check engine light illuminated, Difficulty starting or no start, Engine stalling or rough idle.

What parts fail when P0231 is set?

The most common causes are: Faulty fuel pump relay, Damaged or corroded wiring/connectors in secondary circuit, Blown fuse in fuel pump circuit.

Repair cost breakdown for P0231

It depends on what needs to be fixed. Replace blown fuse and correct root cause repairs are cheaper (~$15), while PCM/ECM repair or replacement repairs are on the higher end (~$1500).

Is the P0231 code specific to Nissan?

The P0231 code is a generic powertrain code, meaning it applies to almost all makes and models, such as Honda, Toyota, VW, Ford, and Chevy.

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