P1633 — Keep Alive Power (KAPWR) Voltage Too Low
CAUTIONIs it safe to drive? Drive gently and get it looked at soon — it can worsen or fail inspection.
What P1633 means
This is a manufacturer-specific code — its meaning depends on the vehicle’s make (see below).
What P1633 means on specific makes
Ford / Lincoln CAUTION
The PCM's constant 'keep-alive' battery feed is too low or interrupted — the module keeps losing its learned memory. Usually a wiring/fuse/ground problem at the PCM B+ feed. Can cause repeated relearns, poor idle after restart, and recurring P1000.
- Blown KAPWR fuse ($5-15)
- Corroded/loose battery or ground connection ($0-50)
- Wiring fault in the keep-alive circuit ($20-150)
- Weak battery ($100-200)
Check first: Verify constant battery voltage at the PCM keep-alive pin and check the related fuse and grounds.
Source: TroubleCodes.net Ford list