P0233
Fuel Pump Secondary Circuit IntermittentP0233 is a generic OBD-II powertrain diagnostic trouble code: Fuel Pump Secondary Circuit Intermittent. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0233 means
P0233 is stored when the PCM detects intermittent or unstable voltage on the fuel pump secondary (feedback) circuit. Unlike P0232 (permanently high) or P0231 (permanently low), P0233 is characterised by a voltage signal that drops in and out unexpectedly — the PCM commands the pump on and sees a steady supply voltage for a period, then the reading momentarily collapses or disappears before returning. This points to connections that are making and breaking contact, a relay with worn contacts, or wiring that is fractured internally but not yet fully open.
The practical consequence for the driver is that fuel delivery becomes unreliable. The pump may cut out mid-cruise, causing a brief stumble or stall, then recover moments later as the circuit re-makes contact. Cold weather, engine heat-soak, or vibration over rough roads often trigger the fault because thermal expansion and contraction aggravate marginal connections. The intermittent nature makes P0233 one of the harder fuel-system codes to diagnose, since the fault may not be present during a workshop inspection.
Thorough diagnosis requires road-testing with live data streaming from a scan tool while monitoring the fuel pump feedback voltage, combined with a systematic wiggle-test of connectors and wiring. Companion codes P0231 and P0232 may appear alongside P0233 if the intermittent fault swings both high and low at different moments. Address harness and connector integrity before replacing the relay or FPDM.
Common causes
Most-frequently reported root causes when P0233 is logged.
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1
Intermittently-failing fuel pump relay with worn or pitted internal contacts that open unexpectedly under vibration or heat.
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2
Loose, corroded, or spread connector terminal in the fuel pump relay socket or at the FPDM harness connector.
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3
Chafed or internally fractured wiring in the secondary feedback circuit that opens momentarily under flexing or thermal expansion.
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4
Faulty Fuel Pump Driver Module (FPDM) with intermittent internal electronics causing erratic output.
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5
Corroded ground connection for the fuel pump or FPDM causing variable voltage drop in the feedback path.
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6
Failing fuel pump drawing excessive current intermittently, causing relay contact bounce and feedback voltage spikes.
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7
High-resistance fuel pump inertia switch contacts (if fitted) introducing intermittent voltage drops.
Symptoms drivers notice
How to diagnose P0233
A typical diagnostic flow when this code is present.
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1
Retrieve all stored and pending codes; freeze frame data showing engine load and speed at fault set helps recreate the condition.
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2
Connect a scan tool and monitor fuel pump feedback voltage in real time on a road test, looking for momentary dropouts while the engine is running.
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3
Wiggle the fuel pump relay, relay socket wiring, and FPDM connector while watching live data — a voltage dropout during the wiggle confirms the fault location.
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4
Remove and inspect the fuel pump relay for arcing, carbon deposits on contacts, or physical looseness in the socket.
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5
Perform a voltage-drop test on the entire secondary circuit from battery positive through the relay and FPDM to the PCM feedback pin.
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6
Inspect the fuel pump ground strap and FPDM chassis ground for corrosion or loose fasteners.
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7
Replace confirmed faulty relay or repair damaged wiring, clear codes, and perform an extended road test before confirming the repair.
Related powertrain codes
Frequently asked questions
Why does my engine only stall sometimes and then restart normally?
Intermittent stalling with normal restarts is the hallmark of P0233. The secondary circuit briefly loses contact — cutting pump power — then re-establishes it. When fuel pressure recovers quickly enough, the engine restarts without obvious fuss. Vibration, heat, or a bump in the road is usually enough to reproduce the fault.
How is P0233 different from P0232?
P0232 indicates a persistently high voltage on the feedback circuit (relay stuck on or wiring shorted high). P0233 indicates the voltage signal is unstable or dropping in and out. P0233 is harder to catch because the fault may not be present on a cold static inspection; live data monitoring during a drive is usually required.
Could a failing fuel pump itself trigger P0233?
Yes, indirectly. A pump with a failing motor drawing erratic current can cause relay contact bounce and create intermittent feedback voltage anomalies. If relay and wiring inspection returns normal results, measuring fuel pump current draw with an inductive clamp will reveal whether the pump is the underlying cause.
Is it safe to drive with P0233?
No. The engine can stall without warning, including at highway speed. Because the next stall may not allow an immediate restart, the vehicle should be diagnosed and repaired before regular use.
Disabling P0233 in software
RaceTune can permanently disable P0233 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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