P0231

Universal

Fuel Pump Secondary Circuit Low

Definition source: General OBD-II reference catalog
Definition verification: Not independently verified for display.
Time: Varies by diagnosis and vehicle | Diagnostic difficulty: Medium
High Severity

The vehicle's control system has detected a low electrical reading in the fuel pump secondary circuit. This circuit is involved in supplying or controlling power to the fuel pump, which moves fuel to the engine. The code identifies an electrical condition, not proof that the pump itself has failed. Depending on the cause, fuel delivery may be unreliable and the engine may run poorly or fail to start.

Report an error with this code

⚠️ Before You Begin (Safety First)

If the engine stalls, loses power, or will not restart, move to a safe place and arrange assistance rather than continuing to drive in traffic. Avoid working on fuel lines or electrical connections with the ignition on, and do not bypass the pump circuit. Have a technician inspect the vehicle if the fault affects reliable operation.

Common Symptoms

  • The engine may crank but not start if the circuit condition prevents the pump from supplying enough fuel.
  • The engine may stall or hesitate if fuel delivery becomes intermittent.
  • Reduced power or rough running may occur if the engine is not receiving a steady fuel supply.
  • The vehicle may start and run normally if the fault is intermittent or does not currently affect fuel delivery.
  • The warning light may be on even when the driver notices no change in how the vehicle runs.

Common Causes

  • A loose, damaged, corroded, or high-resistance connection in the fuel pump secondary circuit can lower the electrical reading.
  • Damaged wiring or an unintended electrical path to ground can affect the circuit reading.
  • A fault in a relay, fuse connection, or other circuit-control component can interfere with power delivery.
  • An electrical fault in the fuel pump may affect circuit voltage or current.
  • A power-supply or ground problem elsewhere in the circuit may produce the detected low condition.

Diagnostic Steps

  1. Record the code and any other stored codes before clearing anything; related codes or freeze-frame data may help show whether the fault occurred during a starting or running problem.
  2. With the vehicle safely parked and the ignition off, visually inspect accessible fuel-pump circuit wiring and connectors for looseness, damage, or corrosion. Do not disconnect fuel lines or probe connectors without vehicle-specific instructions.
  3. If the owner's manual identifies a relevant fuse, check it using the manual's procedure. Replace it only with the specified type and rating; if it fails again, stop and have the circuit diagnosed.
  4. Note whether the issue is intermittent and whether the engine stalls, hesitates, or has trouble starting. Share these observations and the scan data with a qualified technician.
  5. If the code returns or the vehicle runs unreliably, avoid replacing the pump based on the code alone and arrange circuit testing using service information for the exact model, year, and engine.

When to Call a Professional

Confirm the code and review available freeze-frame and scan data. A technician can check the circuit's power supply, connections, wiring and ground, then assess relay or control operation and fuel pump electrical load using vehicle-specific service information. The test results should identify whether the fault is in the wiring, control components, pump, or another part of the circuit before parts are replaced.

Compare component listings

Confirm diagnosis and vehicle fitment before buying. A listing does not prove that a part needs replacement. We may earn a commission from qualifying purchases.

Search Amazon Search eBay

Commonly Asked Questions

Does P0231 prove that the fuel pump needs replacement?

No. It reports a low reading in the fuel pump secondary circuit. Wiring, connections, power supply, ground, control components, or the pump itself can contribute, so testing is needed before choosing a repair.

Can I drive with this code?

It depends on how the vehicle is running. Because an intermittent fuel-circuit problem can cause hesitation or stalling, stop driving if the engine loses power or stalls, and seek assistance.

Why might the code appear when the vehicle seems to run normally?

The electrical condition may be intermittent or may not yet be affecting fuel delivery enough for a noticeable symptom. A stored code and scan data can help a technician investigate when it occurred.

What should be checked before replacing parts?

A technician should inspect the circuit connections and wiring, verify power and ground, and assess relevant control components and pump electrical operation using vehicle-specific service information.

Browse Available Code Guides

Previous and next available guides in database record order, across makes. Adjacent entries may share a code number and do not necessarily describe related faults.