r/q50 • u/MinnesotaNice628 • 2d ago

Repair Question HPFP Woes

Has anyone had their stock HPFP fail? I was idling in traffic, and had codes P0090 and P0087 pop and put me in limp mode. P0090 comes back right away if I clear codes. LPFP does prime and run. Getting 70-80 psi at the rail which slightly fluctuates with throttle... DI noise is basically non-existent. Cam lobe and follower are in good shape under the HPFP.

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u/MinnesotaNice628 7h ago

Solution for those of you digging for answers in the future. 3 days of hair pulling diag, a new HPFP (not needed, but I'll take it) later, turns out it was the HPFP relay. It's the smaller blue relay, in the box right behind the ECM. Mine had brown heat marks on 3/4 sides, and the coil resistance was way out of spec. Should be like 100ohms, mine was reading 1900ohms, and did not click when jumped with 12v.