Fuel Pump Controllers Part 2 - Diagnostics

Fuel Pump Controllers Part 2 - Diagnostics

Feb 17, '23

In part 1, we talked about the basics of a fuel pump controller (FPC), why it's essential, and how it works. This part 2 post will discuss common issues and how to diagnose them.

It's pretty standard for us to get calls and emails about fuel pump-related issues. From our experience, most of them stem from a failed or failing fuel pump controller. Common symptoms include:

  • Check engine light for DTC P0230
  • Car not starting at all
  • After some driving, fuel pressure drops, and the car stalls out
  • Once the car sits for a while, the fuel pump starts working again


This code is a generic error code for the fuel pump controller. There are 2 signal wires for the fuel pump controller, one coming from the ECU to the FPC and a response from the FPC indicating a problem or no problem. The ECU is not logging what the FPC is doing, so the information you see in diagnostic software is purely the ECU request. 

The most common reason for this code is that the ground side of the circuit is fully grounded all of the time. This could be from a shorted wire or a hardwire kit that does not keep the fuel pump controller in play, which is extremely important. We carry a fantastic plug-and-play hardwire kit that keeps the FPC in play. Please click here to read more about our kit.

The Fuel Pump Controller is Not Working at All or Working Intermittently.

There have been several times when people purchased our hardwire kit to fix a fuel pressure problem, and it remained after the installation because the fuel pump controller was the problem to start. The hardwire kit will help mitigate the chances of fuel pump controller failure, but it is not a fix for that issue in itself. 

Commonly the connector on the top of the fuel hanger melts and causes the wiring to fry and the fuel pump to fail. When this happens, it takes out the FPC at the same time. So if the hanger connector is damaged, we suggest replacing the FPC simultaneously.

How to Diagnose if the Problem is the FPC

When diagnosing any problem, the key to success is eliminating variables. So the simplest way to remove the fuel pump controller as a variable is to bypass it. When looking at the connectors, you'll want to jump the ground wire to the chassis to the ground output wire to the fuel pump. This will cause the pump to run 100% anytime the key is in the "on" position. The point is to see if the problem goes away in this scenario. If it does, then your problem is the FPC.

If you have our hardwire kit, this is simple. Unplug the FPC and jump the Black wire going to the ring terminal for the ground to the Blue wire that goes to the pump.

If you do not have our hardwire kit, you'll need to jump both the power and the ground wires. To clarify, power to power and ground to ground. DO NOT jump the power wire to the ground wire! Below are the typical color combinations for these wires are below.

2002-2007 WRX/STi, 2004-2008 FXT, 2004-2006 Baja XT

  • 12V - Black w/Orange and Black w/Yellow
  • Ground - Black w/White and Black.

2008-2021 STi, 2008-2014 WRX, 2009-2013 FXT, 2005-10 Outback XT, 2005-12 Legacy GT

  • 12V - Red w/Black to Green w/Yellow 
  • Ground - Green/Red to Black


We hope these tips help you figure out any fuel or fuel pump controller issues you may have. If it is a different issue, you can check out our general diagnosis tips by clicking here.