Fuel Pump Secondary Circuit Intermittent
Code P0233 indicates an intermittent problem in the fuel pump relay secondary circuit, which controls power to the fuel pump. This means the PCM has detected an inconsistent or faulty signal in the fuel pump relay control circuit, preventing reliable fuel pump operation.
What You Might Notice
- Check engine light (MIL) illumination
- Fuel pump runs with ignition off
- Engine hesitation or stumbling during acceleration
- Hard starting or difficulty starting
- Intermittent loss of power while driving
Most Common Causes
- 1
Faulty fuel pump relay
A defective relay that intermittently fails to engage or disengage, causing inconsistent fuel pump operation and secondary circuit voltage issues.
- 2
Short to voltage on fuel pump circuit
A wiring short to battery voltage on the fuel pump voltage supply or feedback circuit, causing erratic relay control signals.
- 3
Short to ground on PCM relay control circuit
A grounded wire in the PCM's fuel pump relay control circuit prevents proper relay activation and creates intermittent control problems.
- 4
PCM fuel pump relay driver failure
Internal damage to the PCM's fuel pump relay driver circuit shorts to ground, disabling normal relay control functions.
How to Diagnose It
- 1
Check Faulty fuel pump relay — A defective relay that intermittently fails to engage or disengage, causing inconsistent fuel pump operation and secondary circuit voltage issues.
- 2
Check Short to voltage on fuel pump circuit — A wiring short to battery voltage on the fuel pump voltage supply or feedback circuit, causing erratic relay control signals.
- 3
Check Short to ground on PCM relay control circuit — A grounded wire in the PCM's fuel pump relay control circuit prevents proper relay activation and creates intermittent control problems.
- 4
Check PCM fuel pump relay driver failure — Internal damage to the PCM's fuel pump relay driver circuit shorts to ground, disabling normal relay control functions.
How to Fix It
- 1
Replace fuel pump relay
Remove the fuel pump relay from the relay panel and install a new OEM or quality aftermarket relay to restore proper fuel pump control.
- 2
Inspect and repair fuel pump wiring
Thoroughly inspect the fuel pump relay control wires and voltage supply circuit for damaged insulation, corrosion, or accidental shorts. Repair or replace damaged wiring sections.
- 3
Check and clean relay connections
Remove the fuel pump relay and inspect the relay panel socket and pins for corrosion or poor contact. Clean contacts with electrical contact cleaner and ensure proper seating.
- 4
Test PCM and seek professional diagnosis
If relay and wiring checks pass, have a professional diagnostic technician test the PCM's fuel pump relay driver circuit with specialized equipment, as internal PCM failure may require PCM replacement.
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