Fuel Pump Secondary Circuit Low
The P0231 code means the vehicle's onboard diagnostic system has detected: Fuel Pump Secondary Circuit Low. This is a critical severity code.
- Keep driving?
- No -- stop driving
- DIY difficulty
- moderate
- Estimated cost
- $350 - $850 (parts and labor)
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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
-
Measure fuel pump circuit current draw with an amp clamp -- should be 4-8 amps on most vehicles; low draw indicates a failing pump
-
Check voltage at the fuel pump connector with key on -- should be battery voltage (12-14V)
-
Inspect ground wire at the fuel pump for corrosion or high resistance -- should be less than 0.5 ohms to ground
-
Test fuel pressure at the rail -- low pressure under load confirms fuel delivery problem
-
Replace fuel pump assembly if current draw and pressure are below specifications
Common Fixes by Vehicle
What techs usually find when diagnosing P0231 on specific vehicles — tap your vehicle for the fix and the exact part:
2005-2018 Ford F-150/Explorer/Mustang moderate DIY
Fuel pump secondary circuit low means the fuel pump feedback signal to the PCM is below the expected range. This usually means the fuel pump is drawing too little current because it is dying or has a poor connection. Check the fuel pump connector at the top of the tank for corrosion and melted pins -- high current draw through corroded pins causes heat damage. If the connector is damaged, repair it and retest. A pump drawing less than 3 amps indicates internal wear.
Labor: 1-2 hours2008-2019 GM Silverado/Sierra/Tahoe moderate DIY
GM trucks use a fuel pump control module to regulate pump speed. P0231 indicates the pump feedback circuit is reporting low output. Check the fuel pump ground connection at the tank -- a corroded ground causes low current readings. If the ground is clean, the fuel pump is worn and not drawing enough current to maintain pressure. Replace the fuel pump and check for contamination in the tank.
Labor: 1-2 hours2010-2020 Ford Escape/Focus/Fusion moderate DIY
Ford sedans and crossovers have the fuel pump connector inside the trunk or under the rear seat. Check for water intrusion at the fuel pump access panel -- a leaking trunk seal or clogged sunroof drain can drip water onto the fuel pump connector. Dry the connector, clean with electrical cleaner, and apply dielectric grease. If the pump itself is weak, fuel pressure will be low at the rail during a key-on, engine-off test.
Labor: 1-2 hoursFrequently 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.
Sources
This page is built from documented references. Verify against your own service info before repair work.
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