What it means
Intermittent fault on the secondary fuel pump circuit (transfer/lift pump or low-pressure stage). Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
How it works
The fuel pump secondary circuit supplies a pump stage, such as a transfer or lift pump, and the control module monitors the circuit for steady operation. P0233 sets when the circuit signal or operation becomes intermittent, often because a connector or wire briefly loses contact as the vehicle vibrates.
Common causes
Most likely first.
- Connector loose or corroded
- Connector with intermittent contact under vibration
- Harness routed against vibrating component
Symptoms
- Check engine light on
- Hard start, no start, or stalling under load
- Power loss especially at high load or rpm
- Possible long cranking time
How to diagnose it
- Record freeze-frame data and check scan-tool data for fuel-pump command or status changes around the time the fault occurred.
- Inspect the secondary pump connector and harness for loose or corroded terminals, moisture, pin push-back, and chafing near vibrating parts.
- With the circuit operating, gently move the harness and connector while watching the relevant scan data or measuring the circuit for dropouts.
- Check power, ground, and continuity through the secondary circuit while flexing suspect sections, and compare readings with the wiring diagram and manufacturer’s specification.
- If the wiring and connections remain stable, test the pump and its control components using the manufacturer’s diagnostic procedure.
Common fixes
- Secure a loose secondary pump connector and repair corroded terminals.
- Repair chafed wiring and route or secure the harness away from vibration and sharp edges.
- Replace a connector with damaged or unreliable terminal contact.
- Replace a pump or control component only if testing confirms it causes the intermittent fault.
Can I keep driving?
If the engine stalls, is hard to restart, or loses power under load, avoid driving in traffic or on fast roads because the fault can recur without warning. Have the intermittent connection repaired promptly, especially if the vehicle has already stalled.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.