What do I do for a code P1633?

Tiny
NIGHTBLADE53142
  • MEMBER
  • 2008 MERCURY GRAND MARQUIS
  • 4.6L
  • V8
  • 2WD
  • AUTOMATIC
  • 191,700 MILES
Engine light came on one day so I checked the code but I am unsure what I need to do about it. Any advice or help would be appreciated.
Wednesday, June 25th, 2025 AT 6:49 AM

3 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
Yep, this means the voltage in the system is too low, when the engine is running do you have a battery warning light on? If so the alternator might be to blame as it is not charging.

P1633 - Keep Alive Power (KAP) Voltage Too Low

You can use this guide to confirm the alternator is working okay and if so, I would replace the battery.

https://www.2carpros.com/articles/how-to-check-a-car-alternator

Please go over this guide and get back to us.
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Wednesday, June 25th, 2025 AT 12:18 PM
Tiny
NIGHTBLADE53142
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Battery light would come on once in a blue moon but when I tested my battery and alternator the tester said they were good, but the battery is starting to get old so I could try replacing that.
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Wednesday, June 25th, 2025 AT 4:50 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
Okay, also, check all fuses int he under hood fuse panel, you might have one that is out.

This guide can help:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Please go over this guide and get back to us. Check out the images (below).
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Wednesday, June 25th, 2025 AT 6:47 PM

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