Fuel Pump Secondary Circuit Low (Ford)
What does P1238 mean?
The P1238 code means the vehicle's onboard diagnostic system has detected: Fuel Pump Secondary Circuit Low (Ford). This is a critical severity code.
Common Symptoms
- Check Engine Light on
- Engine hesitates during acceleration
- Reduced engine power
- Hard starting especially when warm
- Engine surging at highway speeds
Probable Causes (Ranked by Likelihood)
- Failing fuel pump with low output Very High
- FPDM providing low voltage High
- Clogged fuel filter restricting flow Moderate
- High-resistance wiring in pump circuit Moderate
- Low battery voltage affecting pump operation Low
Step-by-Step Diagnostic Procedure
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Measure fuel pressure at the rail with a mechanical gauge
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Monitor FPDM output voltage under load conditions
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Test fuel pump volume output over a timed interval
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Inspect fuel filter for restriction or contamination
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Check battery voltage and charging system output
Frequently Asked Questions
What does fuel pump secondary circuit low mean?
P1238 means the PCM detected that the FPDM output to the fuel pump is below the expected voltage level, resulting in the fuel pump running slower than commanded.
Can I keep driving with P1238?
You may be able to drive short distances at low speeds, but the engine may stall under load. Avoid highway driving and get the vehicle repaired promptly.
Should I replace the fuel pump or the FPDM first?
Start by testing fuel pump current draw. If current is normal but output is low, replace the FPDM. If the pump draws excessive current, replace the pump first.