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Please vote on fault P1793

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Old 07-02-2018, 07:21 PM
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Thanks all. I am under warranty. I contacted the rebuilder in CA (I'm in TX). They have rebuilts ready to ship, so I asked them if I could order another and send mine back and get a refund. These are original Denso's, so I assume it's not a problem I've heard about with aftermarket jobs when the internals don't match. Whether I could do more testing or not, the Alt has to come out, so might as well have a good one ready to go back in. As I was typing this, heard from the rebuilder. They're shipping a replacement tomorrow...

Also, while probably academic at this point, I still can't see how electrical power can go out when cables are good and you have a fully charged battery. Even if the Alt quits, you still have power from the battery. Lights may dim, and battery light will come on, but most accessories don't know that the Alt's not working, especially with a battery charged to 13-14V. The P1793 code, I'm guessing, set's because voltage < 7V, or it could set because >16V. I'm guessing <7V, as in 0V for a few milliseconds, because everything goes dark. However, IIRC, the battery light does not come on during this very short power loss. One would think cables, except always at the same engine speed??? Stuttering diodes sounds as reasonable as any to me...

Anyway, I think I'm done with testing until I have a good Alt. This <7 or >16V can't be good for the electrical parts and it is easy to avoid... just keep shift points below 2500 rpm. I know, what fun is that?

Regards to All.... Mark
 
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Old 07-02-2018, 10:20 PM
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Actually the ECU in these cars measures the charge and when that charge cannot reach a certain level, you get codes and default modes are instituted if there are any. It is very common to get multiple issues from the battery being low. Thus why I swear by a battery tender when the vehicle sits over a week.
Real glad to hear your alternator source is working with you on this.
 
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Old 07-13-2018, 12:03 AM
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Default Problem Solved and Alternator Replacement

Originally Posted by Highhorse View Post
Actually the ECU in these cars measures the charge and when that charge cannot reach a certain level, you get codes and default modes are instituted if there are any. It is very common to get multiple issues from the battery being low. Thus why I swear by a battery tender when the vehicle sits over a week.
Real glad to hear your alternator source is working with you on this.
You aren’t kidding HighHorse. I experienced the multiple default/ shutdown modes, up close and personal, when my already defective Alt (more on that later) decided to start charging less that it had been, i.e. the battery light HAD been coming on for a second then going off. At the start of a 2 1/2 mile long bridge (I live on an island) the battery light started to light almost continually.

This is the Queen Isabella causeway--same one that collapsed on 9/15/2001, killing eight people-- bet you didn't know that-- no one does because of 9/11—that was the only thing in the news that week and the fatal bridge collapse was largely overlooked.

Anyway, the bridge has no turn-arounds and nowhere to pull over. My Alt fault triggered almost every warning the ECU has-- Stability Control Failure, ABS failure, Gearbox Fault, Check Engine, Airbag Fault, etc. Made it home okay but it was nerve-racking. Had one fault stored, the title one: P1793-- <7V or >16V. What's weird is: battery was still at 12.7V, although it was daylight and I cut off the accessories…

Fortuitously, my rebuilt Alt arrived that same evening. I replace it and All Is Well, see all the stuff outlined in this thread… Problem Solved… thanks for those that voted for Alt… As said, the last thing I wanted to do is replace the Alt if it could have been something else…

But, thought I’d share a quick primer on replacing the Alt. There are plenty of posts on this, but, having done it twice, maybe this will help someone. I chose the wheel-well method.

1. Disconnect the battery and loosen the serpentine belt. The belt tensioner is loosened with a 15 mm socket and ratchet or breaker bar, pulling it toward the center of the engine, like you are trying to loosen the bolt... which you might do.... just retighten it and try again...

2. Remove right wheel and take out some of the plastic pushpin rivets that hold the inner-fender liner in place. (Google it, if you don’t know how to remove a pushpin rivot.) You don’t have to take the liner all the way off, just bend it back enough behind the brake rotor to expose the opening on the right side of the rotor to get to the Alt.

3. You’ll be able to see the Alt air duct from there. From directly under the car remove the 13mm bolt holding the air duct channel, then remove the air duct. The air duct is bolted to the engine horizontally with two 8mm screws (all dim's refer to socket size).

4. Remove the battery cable from the Alt and removed the 13mm bolt and 15mm nut at the bottom of the Alt and loosen the 10mm upper screw. (this isn't as easy as it sounds, but if you have enough sockets, extensions and such, you’ll get it done, just be careful not to strip the 10 mm top screw. If you do, you’re in for a ton of work...)


5. I say loosen but do not remove the upper screw so you can pry the bottom of the Alt out of the bracket.

6. Remove the electrical plug from its socket in the Alt. This also is not as easy as it sounds. With the Alt "swinging", and only the top screw holding it, you can reach the plug easier. You have to squeeze the plug and pull... the release is on the side closest to the engine. Having the Alt pried away from the engine makes squeezing the plug and pulling it out of the socket sooo much easier… Ask me how I know...

7. Remove the Alt through the opening. Pointing the pulley toward the opening seems to work best. (I’ve heard about removing the oil filter, loosen the motor mounts, jacking the engine and other stuff. I found none of that necessary. If you're careful, everything should be accessible and removable through the space you have just by peeling back the inner fender liner and removing the air duct.)

At this point, one would normally say, "install new Alt by reversing the steps." Not necessarily so….

The inboard bottom bracket-- closest to the passenger seat-- has a sleeve or bushing that protrudes into the space where the new Alt will go. Ideally, this sleeve should be pushed out and bolting the Alt back up will push it back in. (best I can figure, this sleeve prevents the bracket from being squeezed or stressed on installation, and provides for "slop" between the Alt and bracket. This is hard to describe and I didn’t understand it when I read about, but you'll know when your new Alt won’t fit in the bracket.)

Others have described making a homemade “press" out of a bolt, nut, washers and a large socket. Not wanting to procure or scrounge for the homemade "press" parts, I simply used a electric grinder on the mating-surface of the bottom on the “new” alt (see pic)…. Not much, probably < 1/32", and don’t grind the other mating-surfaces as that might screw-up the alignment. This is the second time I've done this and there's still enough of the sleeve protruding for it to serve its propose, i.e. prevent stressing/squeezing of the bracket. Maybe next time, I hope that won’t be anytime soon, I’ll have to press the sleeve out, however,-- just guessing here-- I'd say you can "grind" 3-4 times...

Anyway, hope this helps…


Regards…. Mark
 
The Following 2 Users Say Thank You to mcypert For This Useful Post:
Highhorse (07-13-2018), NEECAPR (07-13-2018)
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