Fuel Pump Secondary Circuit High (Ford)
What does P1239 mean?
The P1239 code means the vehicle's onboard diagnostic system has detected: Fuel Pump Secondary Circuit High (Ford). This is a moderate severity code.
Common Symptoms
- Check Engine Light on
- Higher than normal fuel pressure
- Rich running condition
- Fuel odor from exhaust
- Spark plug fouling
Probable Causes (Ranked by Likelihood)
- FPDM stuck in high output mode Very High
- Shorted wiring in FPDM control circuit High
- PCM sending incorrect duty cycle signal Moderate
- Fuel pressure regulator stuck closed Moderate
- Aftermarket fuel pump with incorrect specs Low
Step-by-Step Diagnostic Procedure
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Measure actual fuel pressure and compare to specification
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Monitor FPDM commanded duty cycle vs actual output
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Inspect control wiring between PCM and FPDM for shorts
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Test fuel pressure regulator operation
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Verify correct fuel pump part number if recently replaced
Frequently Asked Questions
What does fuel pump secondary circuit high mean?
P1239 indicates the fuel pump is receiving more voltage than commanded, causing higher than normal fuel pressure and a rich running condition.
Can high fuel pressure damage my engine?
Yes. Excessive fuel pressure can flood the cylinders, wash oil from cylinder walls, dilute engine oil, and damage catalytic converters.
Is P1239 related to a fuel pressure regulator problem?
It can be, but the FPDM itself is the more common cause. A stuck-closed regulator can produce similar symptoms, so both should be tested.