P0231
UniversalFuel Pump Secondary Circuit Low
Medium SeverityThis code indicates that the Powertrain Control Module (PCM) has detected a voltage reading lower than expected in the fuel pump secondary circuit. This usually means the fuel pump is not receiving adequate power, potentially causing fuel delivery issues to the engine.
⚠️ Before You Begin (Safety First)
Always disconnect the battery before working on electrical components. Be aware that the fuel system can be under pressure, so take precautions when disconnecting fuel lines to avoid fuel spray. Ensure proper ventilation when working with fuel.
Common Symptoms
- Engine will not start or cranks but does not start
- Engine stalls immediately after starting
- Poor engine performance or misfires
- Check Engine Light illuminated
Common Causes
- Faulty fuel pump relay
- Blown fuel pump fuse
- Corroded or open wiring in the fuel pump secondary circuit
- Bad ground connection for the fuel pump
- Defective fuel pump
- Issue with the Powertrain Control Module (PCM)
Frequently reported on: General/Universal
Diagnostic Steps
- Check the fuel pump fuse in the vehicle's fuse box and replace if blown.
- Locate and test the fuel pump relay; swap with a known good relay if available.
- Inspect the wiring harness connected to the fuel pump for any visible damage, corrosion, or loose connections.
- Verify proper voltage at the fuel pump connector (requires a multimeter and wiring diagram).
- Check the fuel pump's ground connection for corrosion or looseness.
👨🔧 When to Call a Professional
If basic checks of the fuse, relay, and visible wiring do not resolve the issue, or if you suspect a faulty fuel pump or complex wiring problem, it is best to consult a professional mechanic.
Commonly Asked Questions
What does "secondary circuit" mean for the fuel pump?
The secondary circuit typically refers to the power side of the fuel pump's electrical system, often after the relay, delivering power directly to the pump.
Can a bad fuel pump relay cause P0231?
Yes, a faulty fuel pump relay is a very common cause for P0231, as it can prevent proper voltage from reaching the pump.
How do I test the fuel pump without special tools?
You can often hear the fuel pump prime for a few seconds when the ignition is turned to the "ON" position (before starting). No sound could indicate an issue. A fuel pressure gauge can also confirm lack of pressure.
Is it safe to drive with code P0231?
It is generally not safe to drive with P0231, as it can cause the engine to stall unexpectedly or prevent it from starting, leading to a breakdown.
Where is the fuel pump fuse usually located?
The fuel pump fuse is typically located in either the under-hood fuse box or an interior fuse panel, as specified in your vehicle's owner's manual.