I was driving along tonight at 75 mph on the freeway when my headlights started flickering. I flicked on the high beams, and as soon as I did there was a thunk which I really felt more than I heard. Everything went black! No headlights, no dashboard lights, not even any moonlight. Fortunately that only lasted about a second, then everything came back on. At this point the dashboard had the yellow warning light on and the display read "gearbox fault". The engine was running fine and the car was still drivable, so I chose to keep driving the 22 miles to the hotel rather than pulling to the side of the road and risk having everything die on me and be stranded.

As I took the exit to our hotel it was pretty obvious that the car wasn't downshifting. I drove to the hotel in 6th gear, then parked it. Before I turned off the engine I shifted into R and it went into gear with a jolt. I shifted back into drive and there was another big jolt. Then I turned off the engine long enough to put the top up and started it back up. I shifted into R and then drive and it appeared to shift fine. The warning light and "gearbox fault" messages went away. I just read the codes, and the only code I get is P1000, which I understand is normal.

Also... I drove to the top of Pike's Peak today and the transmission was in 2 or 3 for most of the drive up to the 14,000 foot summit. On the way down it was in 2 most of the way. I don't know if going downhill for 19 miles descending 7000 feet and using the engine for braking could damage the transmission. I drove another 400+ miles after leaving Pike's Peak before the problem showed up. The engine temps were normal the whole time, and I never got any other warning lights before the clunk/power failure.

 

A little bit of reasoning...

1) Since the power and trans problems happened at the same time, let's assume they are directly related.

2) I doubt a transmission failure would somehow cause all your power to go out.

so ... best guess is that an electrical fault caused the lights to go out and caused the trans controller to go off into la-la land. When you shut down then started up, the trans controller is reset, so it then shifted fine.

So onto the power issue ... was it only the lights that went out ... did the engine cut out too? Radio/cdplayer cut out? No lights at all, no dash led display? Where was the thunk?

 

The thunk was obviously the transmission locking into 6th gear. It was stuck in 6th until I rebooted the car. When the incident occurred, all of the lights went out. I didn't have the radio on. The engine may have cut out, but I don't know because at that exact moment the tranny "thunked", and a moment later the lights came back on. The car dropped out of cruise control, but I don't know if the engine stopped running momentarily.

Oh yeah... one other thing. For the remainder of the drive to the hotel, the headlights would spend a few minutes flickering, then they would appear normal for a minute or two. Then they'd flicker again, and so on until I got to the hotel. Every once in a while the dashboard lights would blink off momentarily--literally for a fraction of a second. If I blinked I'd miss it.

I guess you're right. It sounds more like an electrical thing than a transmission thing. I was so worried about the tranny I wasn't even thinking about electrical stuff.

 

Yep, in case you hadn't noticed, your tranny *is* practically electrical stuff. It's all solenoid operated.

So just a quick check, is there maybe something packed in the trunk (boot) that knocked against the main fusebox?

 

Sam, Is there a chance that you have water in your trunk? That main connection box near the spare is pretty low in the trunk. Could be water sloshing around.

 

Sam, this probably has nothing to do with your issue but I'll throw it out there anyway. I has some issues with my headlights flickering also. They would turn off and within a second come back on. It turned out that I had a failing light sensor in the rear view mirror that resulted in the flickering when using the auto headlights setting. However this did not effect any other functions of the car.

 

Sam, I had this same problem but it was midday and no lights were on. The car stalled. I'm going to try and disassemble the trans just as soon as my back allows it. If I find anything I'll shoot you the heads up. -Shaun

 

I agree with Dan you should check the fuse block in the trunk. The blocks have been known to crack and cause several no start and running failures where the car would just stop and not start for a few minutes. I am also thinking as I mentioned before this might be the cause of your other problem and not water in the gas.

 

A photo of the fuse

 

I'll definitely lift up the floor of the trunk tomorrow morning and see if that fuse block looks damaged in any way. I'll even tighten up the nuts a little.

Today was completely uneventful. We drove about 650 miles with no problems. This evening I noticed the headlights flickering and I was a little concerned, so I pulled off at the next exit, turned the car off, waited about five seconds, and restarted it. It was fine the next 90 minutes to the hotel. I have no idea what caused the incident yesterday, but it seems to be doing fine now. I guess it's just one of those weird electrical things that happens with these Jags.

 

Anyone remember this thread?

Well, here we are, three and a half months later, and this weird problem happened again. My wife and I were driving back from Florida this evening and my headlights and instrument panel lights started flickering. I took the next exit because I didn't want a repeat of the last episode. I pulled into a gas station, put the car in park, then I turned on the high beams. The INSTANT the high beams came on the entire car blacked out and the engine died. Fortunately I was sitting at a gas station this time rather than driving down the freeway.

I turned off the key, waited a few seconds, and then restarted the engine. It started fine and it ran fine the rest of the way home (about 200 miles/3 hours). The headlights didn't even hint at flickering.

At least now I know what to do when this infrequent problem occurs. I wish I knew what was causing it, though. I originally thought it was a battery problem but I have a brand new batt and the fact that it didn't recur after restarted the car tells me that it isn't the battery.

 

did you have anything in the trunk that couldve hit the fuse block? and have you checked to see if there was water in the trunk since the last occurrence?

 

No water, and I've been down the fuse block route. That's not the problem. I wish it was that simple.

 

Strange, its power related, obviously. If it wasn't your high beams, it could be anything that pushes the power demand over this 'line' causing full electrical loss. Flickering of the HIDs are obviously the indicator that you are at that line, but why? Is it a random alternator failure? Since you don't have a voltmeter on the dash for the battery, that would be the first thing I would install temporarily. Then, if/when it happens again...did the battery voltage drop dangerously low?

Maybe the belt is slipping from the alternator? Have you changed your serpentine since you owned it?

Just tossing out ideas.

 

I haven't changed it, but I did spray it with belt conditioner a while back. How difficult is it to replace?

 

I just thought of something. Earlier in the day yesterday I got the infamous traction control error a couple of times. I haven't gotten that error since I replaced the battery a couple of months ago. That error coupled with the issue I mentioned above makes me think battery/alternator problem again. I think I'll replace the serpentine belt today just to see what happens. I just looked and Advance has one for $25. It looks pretty easy to replace according to the JTIS.

 

Sam,
The same problem again, sorry to hear that. The belt was easy to change just put your socket on the bolt on the tensioner using a ratchet or breaker bar and push to release the tension. Remove the old and install the new. http://www.gusglikas.com/AutoRepairBeltTensioner.htm I also replaced the alternator but I am not sure that is your problem http://www.gusglikas.com/AutoRepairAltRepair.htm

I think you need to check all the connections to all the fuse/relay boxes. You have a loose connection that will change with temperature and vibration. Check your connections, clean them and I know you do not want to hear this but use the dielectric contact past. It works for me and it can work for you!

 

If this was any other car I would say you have a ground problem. But Jag's have this funny floating ground thing. You still might want to check the ground studs. There are plenty of them.

 

BLASPHEMY!!!

 

Yeah, I agree with it could be a ground on any other car. In these... who knows. The other thing you had in common from before was the length of time you were driving. Last time you were on a road trip and this time you were returning from one -- each time the car was being driven for multiple hours. It hasn't happened just driving it around and to work or that kind of thing -- its only when it has been driven for extended periods. Maybe something's getting warm in the electrical system and then the high beams put it over the limit. Then restarting the car resets everything.... hmm, but whatever it was would still be warm though. Just my random thoughts on it.