P0231 OBD2 Trouble Code ✔️ Check the Fuel Pump and Relay first!

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P0231 OBD2 Trouble Code


Meaning of P0231 Generic OBD2 Code

The technical definition of P0231 code is: Fuel Pump Secondary Circuit Low Voltage

In most cases, it means the fuel pump is not getting the required voltage to pump the fuel.

Pro Tip
If you’re seeing this P0231 OBD2 Trouble Code it’s related to your fuel pump or fuel pump relay. I suggest replacing the Fuel Pump Relay, and checking if the Fuel Pump is going bad. It’s also common to replace the Central Junction (fuse) Box, but this is expensive and not always necessary.
fuel pump relay replacement part
Fuel Pump Relay – especially in Fords, these things love to go bad!

In modern cars, the fuel pump is usually located inside the fuel tank. It receives power via the fuel pump relay. Once the ECU commands the fuel pump relay, it energizes the fuel pump to deliver pressurized fuel in the fuel rail. If the ECU detects a low voltage in the feedback relay, it will trigger the P0231 code. This means the ECU is detecting a lower voltage reading in the secondary circuit or feedback circuit of the fuel pump.

Before moving on, save some headache and watch this video by the boys at Astral Auto Repairs diagnosing this generic fault on a Lincoln. They do a great job explaining WHY the fuel pump relay could be heating up and frying rather than just replacing a bunch of parts!

What causes P0231 OBD-II code?

Most potential causes of this DTC include:

The P0231 code does not always signify a failed fuel pump or bad central junction box! Often times it’s just the fuel pump relay gone bad!

Some vehicles are equipped with a feedback circuit in the fuel pump circuit. If the vehicle is fine and a check engine light and P0231 obd2 trouble code are detected, the problem is most likely caused by a fault in the feedback circuit, which is a wire splice located in close vicinity to the ECU.

P0231 fault code DTC explained

What are the symptoms of P0231 DTC?

The symptoms of an P0231 OBD2 trouble code include:

  • Motor refuses to start
  • Engine stalling upon startup or at random
  • Misfiring
  • Low fuel pressure/inadequate fuel supply

If your vehicle is running well with no severe engine symptoms, you can expect poor acceleration and hesitation due to the inadequate fuel supply. The presence of this trouble code is always accompanied by an illuminated check engine light.

diagnosing a P0231 generic fault code
Bad Fuel Pump Relay, Fuel pump, or Fuse Box… it’s usually one of them.

How much does it cost to fix P0231 fault?

Since P0231 is mostly attributed to wiring problems, the bulk of the cost is attributed for labor and diagnosis.

The mechanic (or you) should check the fuel pump and fuel pump relay. Check for damage, loose connections, frayed wiring, and corrosion. Replace or repair all wiring problems if necessary. All problems related to wiring will probably cost around $50 to $100 depending on the severity of the issue.

In some cases, the check engine light and P0231 code will crop up intermittently and eventually disappear. The cycle will repeat itself after a couple of days or weeks behind the wheel. If this is the case, it is possible to rule out a fuel pump problem. Depending on the type of vehicle, a new fuel pump will cost anywhere from $150 to $1000 excluding labor cost.

Now some mechanics also just replace the entire junction box which can cost from $500-$1000+ bucks. But this is like hunting house flies with a shotgun.

In general, this code has something to do with a wiring issue or fuel pump. If you suspect a low voltage in the fuel pump, it is better to check all related wiring and connectors before buying a new fuel pump. For all you know, the problem can be fixed by a basic wire splicing tool and some electrical tape.


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