Vehicle: 2006 Ford F‑150 Pickup 5.4L VIN 99V
Intermittent drivability issues can be some of the most frustrating problems to diagnose—especially when fault codes won’t clear even during normal operation. Fuel system faults on Ford trucks often point technicians in one direction, but real-world fixes don’t always follow the obvious path. This case highlights how aftermarket parts and assumptions can complicate an otherwise straightforward repair.
Complaint & Initial Observations
The customer reported that the truck ran rough and had low power intermittently. The vehicle also set code P1237, which would immediately return after clearing—even when the engine seemed to be running normally.
The customer explained that the truck had previously died on the road, prompting him to replace the Fuel Pump Driver Module (FPDM) himself using an aftermarket NAPA unit. He also replaced the FPDM pigtail connector. After approximately 50 miles, the truck began running poorly and was brought in for diagnosis.
Initial checks showed fuel pressure within specification, and all related circuits tested good.
Community Insight
A community contributor questioned the assumption that the FPDM was the root cause and asked for actual fuel pressure readings KOEO and KOER. They noted that in many similar cases, the issue was not the driver module at all.
Based on experience, the contributor explained that they had replaced far more fuel pump assemblies than FPDMs for this exact concern, suggesting the pump itself may be failing intermittently despite acceptable pressure readings during basic testing.
Real Fix
Following the community guidance and considering the intermittent nature of the complaint, the technician replaced the fuel pump assembly.
After replacement, the truck ran normally, the rough running and low‑power condition were eliminated, and code P1237 did not return.
Conclusion
This case serves as a reminder that diagnostic trouble codes don’t always point directly to the failed component—especially when aftermarket parts are involved. Even when fuel pressure appears normal, a weak or failing fuel pump can cause intermittent drivability issues. Trusting proven patterns and community experience helped lead to the correct fix and a reliable repair.