I'm here on behalf of my girlfriend. She has a 01' Jaguar s-type 3.0.
She has been having idling problems, then trans problems, then finally power issues. When I ran my code reader on it it came back with a P1633 which is keep alive voltage issues. After some research I have narrowed it down to a computer issue. It does have 190k miles on it with a rebuild trans. Just put in a brand new battery few months ago. My question is, is the PCM bad or could it be something else with it. Not sure if this is a common issue or not.

thanks for any help
Tom

 

Welcome to the forum, Tom. If you haven't done so, please check in at the New Member's section and make an introductory post. Meanwhile....

Please expand on:
Trans problems - actual shifting/operational problems? Or instrument panel indicators?
(Or perhaps she parked on an incline and failed to set the park-brake?)

Power Issues? as in "electrical power?" hence the new battery? Or car runs but has no power?

Your vague description has many hallmarks of a flat battery. Just because it's only a couple months old, doesn't mean it's good.

 

It's almost always bad power / wiring / connectors / damp/water / ... but not the PCM (unless water in it).

As you can't just replace it (beware anti-theft lockout), try everything else.

 

Tom,

Welcome to the forum. P1633 is not a very common fault. From what I understand, when the Keep Alive Memory (KAM) is not working, it means the poor car's computer forgets everything it has learned during the previous drive cycles. That might explain the idle and transmission problems. It's as if the battery had been disconnected before each start, and it takes several drive cycles before the computer fully learns how the car is actually behaving.

2001 wiring diagrams are here, courtesy of Gus:


http://www.jagrepair.com/images/Auto...x2022001en.pdf


A quick web search for "Jaguar S-Type P1633" brought back some interesting results.

1) Check fuse F7 in the Primary Junction Box. This is located outboard of the front passenger (US) footwell. This appears to be the KAM power source. If this fuse is blow, it will also take out the memory for the side mirrors and the driver's seat. Is the memory feature working for those items? Use the little 1 and 2 buttons on the driver's door, just aft of the power window switches.

2) Not all scanners or code readers can fully communicate with the Jaguar computer. Sometimes you need a more advanced model. If your reader can't reset the code, you might be able to find a local shop that can.

As previously mentioned, I highly doubt the computer itself is at fault.

 

Last few days or so there has then some power loss when accelerating. Then following that it started shifting extremely hard. So today on the way to work it wouldn't get past 35 40 miles an hour, when you step on the accelerator it wouldn't even rev up. So I got home get some research hook it up to a battery charger for about 3 hours try driving it and couldn't even get out of the driveway

 

Power problems can easily cause all the things mentioned.

(KAM is critical of course.)

 

What is the voltage across the battery terminals after ten minutes with the ignition off?

Must be at a minimum 12.6 volts, or random electrical faults and DTCs are the result.

 

Are you getting any sort of messages on the dashboard? On the '99-'02 models, I think you'll see "Failsafe Mode" or something like that. It means some critical fault has been detected and engine performance is restricted to prevent damage. If so, you should also see more fault codes logged, too.

On the other hand, most of your current driveability symptoms sound like a transmission issue. Could be as simple as low transmission fluid. The only one that puzzles me is how the engine wouldn't rev up. However, since the engine and transmission talk to each other, the computer may reduce engine power to prevent damage. What about with the car stationary and the transmission in Park? Will the engine rev up then? Don't take it up too high like that. 2000 RPM is plenty. I'm just wondering what sort of throttle response you'll see. There is an RPM limiter when not in gear, maybe 3000 RPM? I don't like to take an unloaded engine up that high, but don't be alarmed if you accidentally bump up against it.

What amperage is your battery charger? I'd suggest an automatic model of at least ten amp output. A trickle charger ain't gonna cut it, especially for only three hours. These cars are very sensitive to battery voltage, so do yourself a huge favor and charge it overnight at a good rate. Always start any troubleshooting with a fully charged battery.

With the engine running, put a voltmeter on the battery terminals. You should see approximately 13.5 volts to indicate the alternator is properly charging.

Have you checked that fuse yet?

 

In '01 car the engine & trans do not talk to each other as the one module (PCM) controls both.

That does not rule out a trans problem but it is low down the list until other things have tested OK.

 

 

Checked the fuses, they are good, I am not getting any message on the dash pertaining to the issue. I will hook it up and let it charge overnight and see what kind of response I get. It doesn't want to rev up when it is in park but it idles just fine. The day before it stopped working I was able to rub it to 2000 RPM and I did not try to go any further.

 

The system will not permit the engine to rev beyond 3,000 rpm with the gearbox in park.