Fuel Pump Secondary Circuit Low
What does P0231 mean?
The P0231 code means the vehicle's onboard diagnostic system has detected: Fuel Pump Secondary Circuit Low. This is a critical severity code.
Common Symptoms
- Engine stalls or dies while driving
- Hard starting or no start condition
- Intermittent loss of power at highway speeds
- Check Engine Light illuminated
- Engine sputters under load
Probable Causes (Ranked by Likelihood)
- Faulty fuel pump with low current draw Very High
- Corroded or high-resistance connections at fuel pump connector High
- Damaged fuel pump ground wire High
- Failed fuel pump relay with intermittent contact Moderate
- PCM fuel pump control circuit issue Low
Step-by-Step Diagnostic Procedure
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Measure fuel pump circuit current draw with an amp clamp -- should be 4-8 amps on most vehicles; low draw indicates a failing pump
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Check voltage at the fuel pump connector with key on -- should be battery voltage (12-14V)
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Inspect ground wire at the fuel pump for corrosion or high resistance -- should be less than 0.5 ohms to ground
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Test fuel pressure at the rail -- low pressure under load confirms fuel delivery problem
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Replace fuel pump assembly if current draw and pressure are below specifications
Frequently Asked Questions
Can I drive with code P0231?
No. A low fuel pump circuit means the pump is not delivering adequate fuel. The engine can stall without warning, especially at highway speeds, creating a dangerous situation.
What does secondary circuit mean for the fuel pump?
The secondary circuit refers to the power side of the fuel pump circuit -- the wiring and connections from the relay to the actual fuel pump motor. A low reading means insufficient current is flowing through this circuit.
Can a bad ground cause P0231?
Yes. A corroded or loose ground connection at the fuel pump increases resistance, reducing current flow and causing a low circuit reading even if the pump itself is functional.