P0231 Low voltage in the secondary circuit that powers the fuel pump

Fuel pump secondary circuit low

P0231 in short

P0231 means the computer sees low voltage on the wire that powers the fuel pump when it should be on. Causes are the relay, wiring, a tripped inertia switch, and on 2003 Ford Expeditions a failing fuse panel. The engine can stall without warning, so get it checked soon and stop if it stalls.

The computer switches a relay, and the relay then feeds power to the fuel pump through the secondary circuit. The computer watches that feed. If it is below about 10.5 volts while the pump should be on, it sets P0231.

TroubleCodes.net lists a faulty relay, damaged or corroded wiring, a broken feedback wire to the computer and a tripped inertia switch as causes. It warns that replacing the pump will not help unless the pump itself is shorted.

On 2003 Ford Expedition and Navigator, Ford has a bulletin for no-start with P0231 or P0232, and owners and mechanics blame the fuse panel in the passenger side kick panel, where solder joints heat up and cut current to the pump.

Most likely causes

  1. Fuel pump relay

    Common general cause
    Why it ranks here
    TroubleCodes.net lists the relay first: a faulty relay passes no voltage to the pump or the monitor.
    What would change this
    Rises if swapping in a known good identical relay clears the fault, or the relay clicks but its output is dead. Falls if the new relay gives the same result.
    How to test the engine controls ignition relay

  2. Damaged, corroded or loose wiring between the relay and pump

    Common general cause
    Why it ranks here
    The same reference lists harness damage causing high resistance, open or shorted wiring, and a broken feedback wire to the computer.
    What would change this
    Rises if voltage at the pump connector is well below battery voltage when the pump is commanded on. Falls if the voltage is near battery voltage.

  3. Tripped fuel pump inertia switch

    Common general cause
    Why it ranks here
    TroubleCodes.net says an inertia switch tripped by even a small impact can cut power to the pump and the monitor wire.
    What would change this
    Rises if the car was recently bumped or jolted and the switch is popped. Falls if the switch is normal and has continuity.

  4. Failing solder joints in the interior fuse panel (2003 Ford Expedition and Navigator)

    Supported by vehicle data
    Why it ranks here
    Three 2003 Expedition owners report P0231 with stalling that clears after the vehicle cools, and mechanics blaming the fuse panel. Ford's bulletin covers no-start with P0231 or P0232 on the 2003 Expedition and Navigator, but its summary does not name the cause.
    What would change this
    Rises on a 2003 Expedition or Navigator if it stalls when hot and restarts after cooling and the pump relay or fuse tests bad. Falls on other vehicles or if the panel tests good.

  5. Fuel system control module damaged by water (2009 GM trucks)

    Possible — needs testing
    Why it ranks here
    A single 2009 Sierra owner reports a stall with P0231 among other codes after water entered the fuel system control module, which the dealer replaced.
    What would change this
    Rises if the truck has a fuel control module near the rear and shows water damage. Falls on vehicles without one.

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Read all stored codes and freeze-frame data. Ask whether the engine has stalled, especially when hot, or not started.

    Low riskTool: OBD-II scan tool

    • IfThe car has stalled or will not start, or it is a 2003 Expedition or Navigator

      It meansHave it inspected soon; the fuse panel is a known suspect on that model.

      Go to step 2

    • IfOnly the light is on

      It meansCheck the simple items first.

      Go to step 2

  2. Check the fuel pump fuse, and check whether the inertia switch has tripped, using your owner's manual to find them.

    Low riskTool: owner's manual

  3. Have a shop swap in a known good relay and measure voltage at the pump connector with the pump commanded on.

    Best left to a shopTool: digital multimeter, wiring diagram

    Warning:The circuit feeds the fuel pump in or near the fuel tank. Sparks or a short near fuel can start a fire, so work only with the battery disconnected and leave it to a shop.

Symptoms

  • Check engine light
  • Hard starting or no start
  • Engine stalls, sometimes when hot, and restarts after cooling Gets more serious: stop and have it checked.
  • Hesitation or a fuel system lean code

How to fix

  1. Check the fuel pump fuse and look at the inertia switch, and reset it only as your owner's manual describes.

    Warning:If you smell fuel, do not reset anything or crank the engine. Keep sparks and flames away and get it towed.

  2. Tell the shop whether the stalling happens when hot and whether you hear the pump prime when the key is turned on.

Parts and cost context

  • Engine controls ignition relay:A relay is the cheapest item to test by swapping with an identical known good relay, but replacing the pump will not help unless the pump is shorted. Labor varies; get a quote.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Ford

  • 2003 · Expedition

    Supported by vehicle data

    Ford bulletin 16079 covers no-start with P0231 or P0232 on the 2003 Expedition, and three owners report repeated P0231 stalling that clears after cooling and blame the fuse panel in the passenger kick panel. Whether the bulletin is still current is not verified.

  • 16079 (ford)Status unverified

    No-start with no fuel pressure and/or fuel pump circuit codes P0231 or P0232

    2003expedition · NHTSA 636279

    Names a no-start with no fuel pressure and fuel pump circuit codes. The NHTSA summary does not say what the repair is.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Lincoln

  • 16079 (lincoln)Status unverified

    No-start with no fuel pressure and/or fuel pump circuit codes P0231 or P0232

    2003navigator · NHTSA 636279

    Names a no-start with no fuel pressure and fuel pump circuit codes. The NHTSA summary does not say what the repair is.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

GMC

  • 2009 · Sierra 1500

    Possible — needs testing

    A 2009 Sierra owner reports a stall with P0231 and three other codes after water entered the fuel system control module, which the dealer replaced.

  • P0230Fuel pump relay control circuit fault

    Same system Supported by vehicle data

    P0230 is the primary circuit fault, the computer's control side of the same fuel pump relay. P0231 is the secondary side that powers the pump.

All Fuel pump and injectors codes

P0231 questions

Does P0231 mean I need a new fuel pump?

Not usually. It is a low voltage fault on the circuit that powers the pump, so the relay, wiring, inertia switch or fuse panel are tested first.

Why does my 2003 Expedition stall and restart after it cools?

Owners report P0231 with this pattern and mechanics blame solder joints in the interior fuse panel that open when hot. Ford has a bulletin for no-start with P0231 on this model; the summary does not name the cause.

Sources and review

  1. P0231 fuel pump secondary circuit low voltage — TroubleCodes.net
  2. Ford 16079: no-start with no fuel pressure and/or fuel pump circuit codes P0231 or P0232 (2003 Expedition and Navigator) — Ford Motor Company
  3. NHTSA complaint ODI 10550793, 2003 Ford Expedition: stalls; P0231 fuel pump relay circuitry code keeps returning — NHTSA
  4. NHTSA complaint ODI 10775890, 2003 Ford Expedition: repeated stalling with P0231, faulty fuse box blamed — NHTSA
  5. NHTSA complaint ODI 11003194, 2003 Ford Expedition: P0231 and the fuse panel solder joints that heat up — NHTSA
  6. NHTSA complaint ODI 10586161, 2009 GMC Sierra 1500: stall after water entered the fuel system control module; P069E, P0231, P025A, P064A — NHTSA
  7. On-Board Diagnostic Trouble Codes (generic code title list) — Delaware Division of Motor Vehicles
Last reviewed
Written by
Saurabh K.
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