Help with P1633 Keep Alive Memory Code

[Glimmertwin34]

I have a 99 GT that gives a P1633 code (Manufacturer controlled Computer and auxillary outputs) is what the OBD II reader shows. I also get a P1451 (manufacturer controlled auxiallary emission controls) I am also having the #8(Engine Controls) fuse blow on a consistent basis that leads to other emission type codes being thrown.

I have checked the battery voltage and it is 12.6V (read a bad battery will throw the P1633 KAM). I also have checked the wiring at every component I cannot find something that is shorting out.

After driving for bit I will get a host of other codes: up to 8 that are emissions related and usually when the #8 fuse blows.

It has all got to be related to one thing that I cannot find and I do not want to start replacing parts if someone can point me in the right direction.

The frustration is setting in & any help would be much appreciated!

Thanks!

 

[wmburns]

Fuse F2.8 blows; look for fault in O2 heaters

Tell us about the mods. Is there a custom tune? Do you have long tube headers?

My advice. Ignore all of the DTC codes until you find the reason that fuse F2.8 is blowing.

F2.8 is blowing because a sensor is drawing too much power or there is a fault in the wiring harness. Are you using the correct O2 sensors for your application? They have two different heater sizes.

Inspect the wiring harness. Look for cut/chaffed/burnt/crushed wires. Pay special attention to any mods such as wiring harness extensions. Pay SPECIAL attention to the O2 sensor pig tails as prob the most common reason for this problem is a melted wire to the O2 sensor that shorts out the O2 heater.

If you still can't find it, disconnect the O2 sensors one at a time until the fuse stops blowing. Start with the rear ones first.

OBTW, the following devices share fuse F2.8. So it is not a surprise any DTC related to any of these sub-systems occurs.

EVAP purge solenoid (Vapor management valve in right hand wheel well area)
EVAP canister vent solenoid (behind left rear tire near gas tank).
EGR vacuum regulator solenoid (top of engine)
O2 heaters (ALL FOUR OF THEM).

OBTW, 12.6 volts in a running car is too low. Today's computer controlled cars simply will not run correctly without a strong battery and charging system.

Is the top of the battery clean? Are the battery terminals clean and tight? Take the car to your local autoparts store and have the battery tested. While there test the alternator. Also test for excessive AC ripple.

Do yourself a favor. Don't cut corners on the health of the charging system.

 

[Glimmertwin34]

Thanks

Thanks for the advice. I'll go through everything again this weekend and if I cant find a short; I'll start disconnecting the O2 Sensors one at a time.

No long headers...short headers.

Battery is spotless, terminals always maintained, no loose cables anywhere. Car always starts fine, but I know that 12.6V is low and will replace it. Altenator was replaced about a year ago, but I will check it. I checked wiring harness & ground at the PCM and found nothing that looked odd or loose.

I knew other codes were being thrown because of the #8 fuse....only thing that made sense, because when I would take the fuse out I would get those codes. No codes with new fuse except the KAM code until fuse blows.

Tomorrow will be a day of going through it all; I'll let you know what I find.

Thanks for the advice.
Jim

 

[Glimmertwin34]

I checked all the wiring....can't find anything that looks burnt, crushed or damaged. I replaced all the O2 sensors with new OE ones. I can put the car in park and let it idle all day long...rev the engine etc... and the fuse does not below. As soon as I put the car in gear and push on the gas "POOF" the #8 fuse blows! Any ideas why it could be doing this? This is driving me nuts!

Thanks,
Jim

 

[Glimmertwin34]

One other footnote...I had unhooked them one at time while it was on jackstands and let it idle forever. The fuse did not blow so I figured it had to have been a bad O2 Heater. That is why I replaced them all. It was after I put the new ones in that I discovered the #8 fuse was blowing when I put it in drive and pushed on the gas....it happens with it up on jackstands.

Thought I would add that in case it makes a difference.
Jim

 

[wmburns]

I am afraid that because the fuse doesn't blow until placed into gear, it is going to be more difficult.

Disconnect the EGR solenoid, CV vent solenoid, both rear O2 sensors. Drive the car, does the fuse blow?

If yes, then the problem is in the front O2 sensors, VMV valve, or the wiring harness itself.

If no, then the problem is in the stuff already disconnected. Now connect the rear O2 sensors one at a time. Does it blow? Now do the EGR. Finally the CV vent solenoid.

Get yourself a big pack of fuses.

 

[Glimmertwin34]

I unhooked everything. The #8 fuse still blew. I unhooked the front O2 heaters. The fuse blew.

When I put it in reverse...I can floor it and go backwards for as long as I want and the fuse will not blow. As soon as I shift into any drive gear and push on gas pedal....POOF....it blows!

Not sure if that helps to narrow it down...but it sure seems odd to me if it were in the wiring harness wouldnt it blow in reverse too?

Thanks,
Jim

 

[wmburns]

I unhooked everything. The #8 fuse still blew. I unhooked the front O2 heaters. The fuse blew.

When I put it in reverse...I can floor it and go backwards for as long as I want and the fuse will not blow. As soon as I shift into any drive gear and push on gas pedal....POOF....it blows!

Not sure if that helps to narrow it down...but it sure seems odd to me if it were in the wiring harness wouldnt it blow in reverse too?

Thanks,
Jim

Did you actually unhook EVERYTHING on circuit F2.8 and it still blew? This is an important point. Getting this wrong is going to cost you a lot of time chasing wild geese.

List everything disconnected and confirm if fuse F2.8 blows. Just want to confirm that everything means everything. Not sure from the post if the VMV, EGR solenoid, or CV vent solenoid has been disconnected.

Have you done any mods to the electrical system? Speedcal? Wiring harness extensions? Anything?

Did you get the alternator tested as requested? What is the battery voltage while the car is running?

Regarding other methods, unless you are prepared to get a DC Clamp on AMP meter an an ODB2 scanner, I do not know any short cuts to your problem.

Further, since your problem is dynamic, static wiring harness tests may not be effective. One tool is to perform harness "wiggle" tests to see if the source can be found.

With a DC clamp on amp meter and an ODB2 scanner, you could relate what the PCM is doing to the actual load on the circuit.

If you are good with a VOM, it might be handy to extend the F2.8 fuse from the CJB. This would make it possible to insert a shut style amp meter in line with the circuit. This will give you a direct measurement of the current. Then various sensors could be disconnected/connected an the results measured.

There is a part of me that thinks this is a damaged wiring harness (don't discount the possibility of rodent damage). But since you have not been able to find any signs of damage, then the process of elimination is all that is left.

Review the following thread for some ideas regarding how to trouble shoot a wiring harness problem. No doubt about it. This can be the BIGGEST PIA possible.

http://www.stangnet.com/mustang-for...l-rpms-stay-high-after-letting-off-pedal.html

 

[Glimmertwin34]

Sorry I have not responded. I have been out of town for a month. I did replace the alternator and battery and am getting 14.86 volts.

I did disconnect everything and the fuse still blew but it only blows when I put it in drive. I could drive in reverse all day long and it will not blow. When I put it in drive at an idle it is fine. As soon as I step on the gas it blows.

I am at a real total loss here 'cause I would think if it were a short it would not matter what gear it was in. Could it be something in connection with the transmission or possibly in the PCM?

Thanks for all of your help so far. I am willing to go at this thing as long as possible...it is a personal thing now!

Thanks,
Jim

 

[wmburns]

We need a toe hold on this or it will NEVER get fixed.

I have the feeling there is some of the car's history not mentioned. Is this an manual/automatic conversion?

Are POSITIVE there isn't any rodent activity? Water damage? Wreck? Nitrix install? Sound system? Speedcal?

Anything happen just between the last time it worked OK and now?

I can't say it strongly enough, this going to be a HUGE PIA. Wiring problems do not happen in a vacuum. There is usually an external factor at work. This may leave evidence on the outside of the wiring harness. If this evidence can be found by visual inspection, this will give us a toe hold needed.

I am unable to think of any system that would change state in drive under load. Which then leads me to think PCM.

 

[Glimmertwin34]

There is a sound system different receiver with pigtail adapter to match factory and amp w/subs in the trunk on seperate, independently wired fuse system.

It is an automatic.

Nothing unusuall that I can think of. It has never been wrecked (I bought it new). The only thing that I can possibly think of is that I have bumped hard on a couple of bumps on the country roads I have to drive to work.

Why would it only blow when I put it in drive? I backed all the way down my street (about a 1/4 mile) giving it gas as I went. The fuse was fine. As soon as I put it in drive and barely touched the gas; the fuse blew.

Crazy eh?
Jim

 

[wmburns]

I don't normally do this so quickly. But IMO this is likely to be a PCM problem. At the very least, this will require a PCM break out box that is above the limit of the average home mechanic.

Check out the relatively few list of items to check out. What's number 2? I think you should consider going to the dealer. With absolutely NO evidence of wire harness damage, then it is likely to be the PCM anyway.


>>>
P1633 - Keep Alive Power Voltage Too Low

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

Open KAPWR circuit
Damaged PCM
Intermittent KAPWR Circuit

 

[Glimmertwin34]

Thanks for all of your help. I will probably take it in this week. I am going to inspect all the wiring one more time and hope....really hope....that I overlooked something. I don't think so as I have looked and re-looked many times.

I'll let you know what the end result is!

Thanks again!
Jim

 

[Glimmertwin34]

It was a PCM problem! I got another one had it programmed and it now runs like a raped ape again! There was damage to the main chip in it!

Thanks for your help!