What causes P1635 on a Ford?

Aftermarket axle gears installed without PCM update Oversize tires changing the effective ratio Wrong tire size programmed after a swap Failing vehicle speed input confusing the ratio check PCM calibration mismatch

How do I fix P1635 on a Ford?

Confirm actual tire size and axle ratio against the door sticker Check what ratio and tire revolutions are programmed in the PCM Reprogram the PCM for the installed gears and tires Verify the speed signal reads correctly on a road test Return to stock sizing if programming cannot accept the change

P1635 Tire/Axle Ratio Out of Acceptable Range

Q: What does P1635 mean on a Ford?

P1635 — Tire/Axle Ratio Out of Acceptable Range. Applies to F-150, Super Duty, Explorer, Expedition with changed gears or tires.

Category: Powertrain - Computer and Auxiliary Controls
Severity: Check Engine Light
Applies to: F-150, Super Duty, Explorer, Expedition with changed gears or tires

What does P1635 mean on a Ford?

P1635 — Tire/Axle Ratio Out of Acceptable Range. This Ford-enhanced code applies to F-150, Super Duty, Explorer, Expedition with changed gears or tires.

Common causes of P1635

Aftermarket axle gears installed without PCM update
Oversize tires changing the effective ratio
Wrong tire size programmed after a swap
Failing vehicle speed input confusing the ratio check
PCM calibration mismatch

How to fix P1635

Confirm actual tire size and axle ratio against the door sticker
Check what ratio and tire revolutions are programmed in the PCM
Reprogram the PCM for the installed gears and tires
Verify the speed signal reads correctly on a road test
Return to stock sizing if programming cannot accept the change