P0233 Code: Fuel Pump Secondary Circuit Intermittent

What the P0233 code means

The computer turns the fuel pump on through a relay or a dedicated pump control module. When you turn the key on, it runs the pump for a few seconds to build pressure in the fuel system, then keeps it running as long as the engine is turning. On many newer vehicles it also varies the pump speed to match what the engine demands.

The P0233 code is set when that circuit opens or cuts out intermittently. The computer watches the voltage at its own control transistor, called the driver. With the driver off it expects to see supply voltage, and with the driver on it expects the voltage to drop to almost zero. Any other combination tells it the circuit is open or shorted.

The fuel pump is one of the most demanding electrical loads on the vehicle. A connector with high resistance heats up, melts and lowers the voltage that reaches the pump, so the pump spins slower and delivers less fuel. That is why a lot of failures that look like a bad pump turn out to be a bad connector, ground or relay.

Always check the wiring and the power supply before you replace the part. They are the most common cause and the cheapest to fix.

P0233 code symptoms

• Check engine light on.
• Hard starting, hesitation or an engine that stalls.
• The engine cranks but does not start.
• Loss of power under load.
• You do not hear the pump hum when you turn the key on.

Likely causes of the P0233 code

1. Loose connector. Pins that lose contact with vibration are the usual culprit.
2. Damaged wire that is broken inside its insulation.
3. Relay with worn contacts that sometimes fails to close.
4. Intermittent component failure, for example one that only acts up when it is hot.

How to diagnose the P0233 code step by step

1. Command the pump with the scan tool and check whether it responds with a click, a hum, movement or pressure.
2. Check the fuse and the relay. Measure voltage on both sides of the fuse, and swap the relay with an identical one to test it.
3. Measure the supply voltage at the connector. You should see battery voltage with the key on, or while the pump is being commanded.
4. Measure the pump resistance and compare it with the service manual. Also check the insulation to ground, which should read infinite.
5. Check the control wire. Continuity back to the computer should be under 1 ohm, and the wire should not be shorted to ground or to 12 volts.
6. Listen for the pump when you turn the key on. It should run for 2 to 3 seconds.
7. Measure fuel pressure at idle and under load.

How to fix the P0233 code

• Repair the connector, the wiring or the power supply.
• Replace the fuel pump if it does not respond when power and control are both correct.
• Clear the codes and confirm the repair with a road test.

Technical reference data

• Pump supply: 12 volts through a relay or a module, sometimes with PWM control.
• Typical pump current draw: 4 to 8 amps.
• Typical pressure: 3 to 4 bar (about 44 to 58 psi) on port injection, and 4 to 6 bar (about 58 to 87 psi) of low side pressure on direct injection.
• These are reference values only. Check the manufacturer data for your engine.

Brand-specific notes

Intermittent fuel pump cutouts are usually caused by the pump connector or by the ground at the rear of the vehicle.

Frequently asked questions about P0233