Warning: That 'simple' fuel rail pressure sensor took me 6 hours to find

Had a 2012 Freightliner Cascadia come in last month with a no-start condition and intermittent stalling. Scanned it, got a fuel rail pressure code, and assumed it was the CP4 pump. After swapping the pump and still having the issue, I spent 3 more hours chasing wiring and checking grounds. Turns out it was a bad fuel rail pressure sensor that tested fine cold but failed when warm. Took me 6 hours total for what should have been a 1 hour diagnosis. Has anyone else had a sensor pass a cold test but fail hot?

3 comments

3 Comments

grace_campbell1mo ago

Stick with the diesel guys who told me years ago to always check sensors when they're hot first. Heat cycling messes with internals in ways a cold multimeter reading just won't catch.

hart.sage1mo agoMost Upvoted

Hold up though, what about checking the ground path first? I've seen a bad ground on a hot sensor give false readings that made people replace perfectly good parts.

emery_flores1mo ago

Buddy of mine replaced an alternator three times before finding a loose battery cable.