P0628

P0628 means the Fuel Pump Driver Module (FPDM) — the PWM-controlled driver between the PCM and the in-tank fuel pump — is reporting its control circuit pulled low (shorted to ground, open low-side driver, or commanded duty cycle not matching feedback). On a returnless PWM fuel system the PCM commands the FPDM via a duty-cycle signal (0-100% PWM) and the FPDM regulates pump current accordingly — healthy current draw is roughly 5-15A depending on rail pressure demand, and the feedback line back to the PCM should pulse-width-match the command within a few percent. Shop-floor ladder, cheapest first: pull the FPDM connector (usually frame-rail or rear-bumper mounted on Ford trucks) and inspect for corrosion and chafing — that alone is the fix on 60%+ of Ford F-150 FPDM tickets. Scan-tool live data should show commanded fuel pump duty cycle and FPDM feedback side-by-side; if commanded duty rises to 80-100% on cold start but feedback flatlines or reads 0%, the FPDM output stage is dead. Backprobe the control wire from PCM to FPDM with a scope — you should see a clean PWM square wave varying with pressure demand; a flat low signal points to a shorted-to-ground wire or a failed PCM driver. Next is fuel pressure at the rail with a mechanical gauge (port-injection target 35-65 psi; direct-injection low-pressure side 50-90 psi). Expensive-misdiagnosis caveat: don't drop the tank for a fuel pump on P0628 until the FPDM is confirmed dead — on Ford trucks the FPDM is a $100-200 frame-rail part and replaces the pump in roughly half of P0628 cases without ever touching the tank.

Vehicle-specific patterns: 2011-2016 Ford F-150 EcoBoost 3.5L (and the 5.0 Coyote / 5.4 Triton variants on the same platform) is the textbook P0628 vehicle — the FPDM bolts to the frame rail behind the rear wheel and corrodes from road salt, with chafing where the harness crosses the frame; a relocation kit plus a new FPDM is the standard fix. 2007-2014 Lincoln Navigator and 2009-2014 Ford Expedition share the same FPDM platform and the same frame-rail corrosion failure mode. 2014-2019 RAM 1500 EcoDiesel 3.0L commonly throws P0628 from a failed fuel pump control module under the rear seat — the high-pressure pump side of the system uses a different controller but the low-pressure lift pump driver fails the same way. 2008-2013 Ford Mustang GT 4.6L/5.0L throws P0628 from the same FPDM family with slightly different mounting but identical chafing failure mode. Estimated repair: $200 (FPDM + harness repair DIY) to $1,200 (FPDM + in-tank pump + labor).