p1633 & pcm pin reading

deathwishracer

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So, recently started getting cel that will not clear. Comes on a few seconds after starting, for keep alive memory voltage too low. I have 12.5v plus at the B45 pin, which is the correct one as well as I can tell. Also have 12.5v plus on the wire going into the plug when it is plugged up and the car is running. Ford manual says to replace pcm at this point. Car runs great, no issue other than the light. Anybody have any experience with this? Does the cel mean that the car is in a "limp" mode? Will it hurt to run the car? Is the tune affected at all? Don't mind replacing the pcm, if that is definitely the issue.
 

GT-FeVer

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I know this an old post, but I am having the same problem. Did you ever figure this out? I t is driving me crazy. Alternator went out. I bought a rebuilt one and it was bad, so I am on my second alternator and the bearings are squeaking in it.
Went to get it inspected and it failed. System not ready so the inspection test couldn't run. Got home and had the dreaded CEL light. Code P1633 KAM voltage too low. Checked fuses, and voltage and it all looks fine. What a headache.
 

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What are you getting for battery voltage? The system needs 13.8v+ with the engine running for things to work right.
 
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GT-FeVer

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12.7 with engine off. 14.5 with engine running.
That is what it read yesterday. I did notice the other day it was 12.6 volts at idle.
When the alternator went out I limped it home on the battery. Maybe there is a bad cell in the battery? It starts up with no problems every morning.
I will check the voltage during startup and see if it is dropping way down this evening.
Thanks for the reply.
 
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redfirepearlgt

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May wish to read this on the topic. According to this the KAM memory power source is on pin 55 of C175 connector. F122 is a 10 AMP fuse that supplies the voltage to the PCM at ALL times (Hot at all times). Here's the link hope it is for the correct year. It has the diagnostics section from Ford in there along with pin-out and fuse box location for F122.

http://www.justanswer.com/ford/21ups-getting-p1633-code-cleaned-battery-terminals.html
 

GT-FeVer

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May wish to read this on the topic. According to this the KAM memory power source is on pin 55 of C175 connector. F122 is a 10 AMP fuse that supplies the voltage to the PCM at ALL times (Hot at all times). Here's the link hope it is for the correct year. It has the diagnostics section from Ford in there along with pin-out and fuse box location for F122.

http://www.justanswer.com/ford/21ups-getting-p1633-code-cleaned-battery-terminals.html

Thank you, I did look that over and it is correct about the pin 55. I will check that this evening too. Once I figure this out I will be sure to let everyone know what happened in case it happens to anyone else. I hope it doesn't.
 

GT-FeVer

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I checked the voltage at the battery while someone started it. I saw it drop to 8 volts and jump back to normal once the car started. Possible a battery going bad? Guess I need to have it tested
 

redfirepearlgt

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Three likely candidates come to mind. The battery obviously as you mention. You also may wish to check connections between the battery and the starter. If high resistance is present that could cause a sag while the starter is turning over the engine. The starter itself could be getting tired and causing the sag as well. And while the car is running check the AC ripple across the alternator to make sure it is not exceeding 500 mVAC or .5VAC in AC output. Then verify 13.8-15 VDC output on same.

This is assuming that with key on engine off the voltage is above the 10.5vdc needed per the instruction to maintain KAM data.
 

GT-FeVer

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Thanks my friend. It is so nice to have a place to come to and get fresh ideas and info.
I will check it all out
 

GT-FeVer

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Well, installed a new battery, and a new serpentine belt. Checked all my cables. Code P1633 still there.
I did find the PCM pin-out schematic for the car though and will be checking that this weekend. I sure hope the PCM isn't bad.
 

GT-FeVer

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It's fixed!
Before I share the stupidity of what caused this whole thing, I want to say thank you to you guys for the advice and tips you gave me. It was a big help. Also to that run this website for giving us a place to come and do this.
Okay, I found a webpage that had every diagram I needed including the PCM pin-out.( If anyone needs this or the website let me know). So I began testing voltage from on the pin. Nothing. I knew then I wasn't going to need a new PCM. Phew.
Now I figured since all the fuses tested out fine it had to be a bad connection or wire. So I did the wiggle test on all the wires. Still no voltage. Took a break and went back to it. I had the diagram of the fuse box so I decided to go through it again.
Got to looking at the drawing and counted 5 fuses in the area where the KAM fuse goes. I looked at my box and only counted 4 fuses. What the crap? I tested the empty slot and what do you know? 12 volts. I grabbed another fuse, plugged it in, put everything back together and cranked her up. NO code! I am so freaking happy.
Now I have not removed any fuses, but I had new tires put on two weeks ago. This code came on right after they put my tires on. While in the shop I saw one of the workers jump starting my car. I asked him why and he admitted leaving my key on for 3 or 4 hours with the radio playing.
Only thing I can guess is he had to have messed with those fuses and pulled it out. No one else has been under my hood. Doesn't matter now though it works again.
Again thanks guys.
 

redfirepearlgt

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^^^ It's easily done. I'm going to talk to a friend of mine who manages a tire store and see if resetting KAM is the quick was of resetting the tire pressure sensors rather than doing them one at a time. I am suspect that there is or a tire changer would have had no other reason to be in the BEC for a dead battery. I'll follow up.

I run into issues like this at work going in to finish something someone else has started on and they don't document what has been done up to that point. Fought trying to bring an axis drive imotor on a 5 axis machining center back to life and establishing zero position after 4 months of rebuild work last week for 3 hours before I figured out the tech working on it previously had disabled scale feedback which was what was fighting me. Amazing what the meddling of another can do.

Glad you got it resolved.
 
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