Fuel Pump Secondary Circuit Malfunction (Ford)
What does P1237 mean?
The P1237 code means the vehicle's onboard diagnostic system has detected: Fuel Pump Secondary Circuit Malfunction (Ford). This is a critical severity code.
Common Symptoms
- Check Engine Light on
- Engine cranks but will not start
- Intermittent engine stalling
- Reduced fuel pressure at the rail
- Sputtering under acceleration
Probable Causes (Ranked by Likelihood)
- Fuel pump driver module internal failure Very High
- High-resistance connection at fuel pump connector High
- Fuel pump drawing excessive current Moderate
- Ground circuit fault at the FPDM Moderate
- PCM secondary fuel pump driver circuit failure Low
Step-by-Step Diagnostic Procedure
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Measure voltage at fuel pump connector while cranking
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Test fuel pump current draw with an amp clamp
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Inspect FPDM ground connection for corrosion
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Check fuel pump connector pins for heat damage
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Monitor fuel pump duty cycle with a scan tool PID
Frequently Asked Questions
What is the fuel pump secondary circuit?
The secondary circuit is the high-current output side of the fuel pump driver module that directly powers the fuel pump motor. A malfunction means the pump is not receiving proper voltage or current.
Can a bad fuel pump cause P1237?
Yes. A failing fuel pump that draws excessive current can overload the secondary circuit. However, the FPDM itself is the most common cause.
Where is the FPDM located on a Ford?
On most Ford trucks and SUVs, the FPDM is mounted to the frame rail near the spare tire or fuel tank. On cars like the Fusion, it is typically near the fuel tank.