2000 Taurus I have a Taurus with the same trouble code you posted. I was wondering if you found out what the code (P1633) meant and what to do to correct it. Kelly

check battery and alternator and connections ------this code goes pops when battery disconnected [ from starter replacement? ] https://autoservicecosts.com/obd2-codes/p1633/

P1633 - Keep Alive Power Voltage Too Low

Indicates that the Keep Alive Power (KAPWR) circuit has experienced a power interrupt.

Possible causes:
-Open KAPWR circuit.
-Damaged PCM.
-Intermittent KAPWR Circuit.

First thing would be to check the fuse associated with the KAP. In your case, that would be fuse #22 (10A). If you're A/C doesn't work, then that's why. Usually the A/C clutch causes the fuse to blow and your get your P1633 code.

If the fuse is fine and the A/C works, then it might be a bad PCM. If the battery was bad before it might have set this code. Have you tried clearing the codes to see if it comes back or not?

Ford Taurus model???
this is for ford T 2000
p1633 keep alive memory test failure

Possible causes - Open Keep Alive Power (KAPWR) circuit - Faulty Powertrain Control Module (PCM)

Read more: http://www.engine-codes.com/p1633.html

CODE P1633 - PCM KEEP MEMORY VOLTAGE TOO LOW. WHEN YOU SEE THIS CODE THE PCM HAS DETECTED THAT THE KEEP ALIVE MEMORY POWER CIRCUIT TO THE BATTERY WAS INTERRUPTED.

The P0511 code is for the idle air control circuit and the P1633 is stating the the KAM voltage is too low. My guess is if you are having issues with the Idle air control circuit this could cause stalling, especially if the valve is not functioning properly and allowing too much air at idle, this causing the car to stall. I can't imagine that by pulling the connector on the A/C compressor you would get either of these codes. Have you checked for corrosion on the battery or proper battery voltage level? Here is a forum that may be of some help for trouble areas to look for (regarding P1633): http://www.taurusclub.com/forum/82-maintenance-repair/132098-trouble-code-p1633-kam-too-low.html
As far as P0511 goes if you notice any hooting type noise that is a sure indicator of a faulty IAC valve, if not then I would say first check that you do have proper output from your battery/alternator and then either take it to get properly diagnosed or try to check the circuit yourself.

When the Taurus PCM (Powertrain Control Module)(aka "the car's computer"), sees 9V DC (or less),
it sets the code P1633, so it means your battery's voltage was low recently. But since the computer
retains the code until it is reset, the battery voltage may be OK now. This is typical for cars
that have sat for awhile, and the tiny current drain of the clock slowly drains the battery until
the voltage drops below 9 Volts. Normal car Battery voltage is 12 Volts.
Fix: check the battery (with a DMM (digital multimeter)), and reset the code (with a code reader).
Workaround: have Advance/Autozone/PepBoys check the battery (free) and ignore the code.

The code is for ( Keep Alive Power Voltage To Low ) Description: is the KAPWR has experienced a power interrupt. Possible problems: Open KAPWR circuit... Damaged PCM ...or a intermittent KAPWR circuit