99 XJ8 VdP

Hi All,
I'm reaching the end of my rope with my on-going Stability Failure / Engine Failsafe Mode problem. They have been plaguing me on and off for the last year or so, but now they are getting to a 'Donate-the-car' point.

Problem is when driving happily along, I suddenly drop into the restricted mode of operation, and the degraded drivability of it makes it somewhat hazardous to driving on the local freeways and byways. I can usually feel it coming as the engine performance degrades about 1 second before the amber & red warning lights come on and the messages ' Stability Control Failure / engine failsafe mode (think that's it) come on and I have to negotiate through lanes of high-speed traffic, hoping there's a shoulder available on the side of the road. If I go through the ignition on, then off, then remove key and repeat process anywhere from 5-7 times, it seem to reset itself and will start and run again.
- It has been flat-bedded to the local (55 miles) Jaguar facility and hooked up to the jag-specific OBD reader -- and no codes were shown! Twice I've done that, nothing showed at all.
- Testing indicated the battery was slightly lower than optimum - so a New one was put in.
- An occasional 'rear bulb failure' occurs on braking, another push of the pedal fixes it. No bulbs are out, all have been replaced
- The tech (who owns one, same year and model) and works exclusively on them, thinks it may be the 'security control module' with an issue for this
- Question, would this cause said problem?
- It happens at low speed (20mph), mid-speed (45mph) and high speed (65-75)
- It happens with all cabin electrics (radio, / AC ) on and off.
- It happens under full electric load - lights /AC / Radio / all interior lights / Engine fans both on
- It Happens with ASC both on and off
- It can happen within 30 seconds of a previous event, or as long as 1500 miles between
- I have floored it and taken it up to 5000rpm and 90mph with nothing happening

- I have removed each wire connector on all four wheels (wheel speed sensor?), cleaned them, replaced them and resealed around each connector.
- I have replaced the battery.
- Yesterday I removed, cleaned, replaced each connector (I could reach) around the throttle body (have yet to drive since then)
- I have cleaned and tightened each ground connector I found around the battery.

Since I get no indication lights, I'm starting to suspect the 'Stability Control Failure' message is secondary, and the Engine Fail safe is more indicative - but that's just a gut feeling

It throws no warning lights - ABS, Check Engine, nor any other.

I'm suspecting it may be a grounding issue or a marginal connector issue, spurious data and so it goes belly up.

I can't afford to start - nor is it prudent troubleshooting - to start replacing components *****-nilly.

So, that's the sad story. I'm looking for info and advice from others who may have suffered similarly to aid in T/shooting and eventual fix. I've set a time limit of mid-May to have it fixed, otherwise it'll be donated to one of the Cars-for-xxxx organizations.

So what say ye Gentlemen?

Ken
99 XJ8 VdP
Maricopa, Sonoran Desert, Arizona

 

It would be worth your time to clean the ground points in the engine compartment, the forward cabin gnd points and the engine to frame ground strap ends. Corroded gnd points can cause voltage fluctuations.

 

There's 2 things you should look at, that are free and fairly easy. I've had the rear bulb failure symptoms same as you on my 98 XJ8, and at some point in the past I've seen restricted performance issues as well.

You should remove your brake switch attached to your brake pedal stalk and WD40 it really well. Replacement is an option, but I've had good luck just cleaning mine. I've done it twice on mine about 3 years apart, and it will has fixed my bulb failure ghost both times. Replacement is inevitable I'm sure, but I'll keep cleaning it as long as it keeps getting me results.

I also see no mention in your post of checking the positive battery cable connection at the false firewall on the passenger side. Check with a VOM on either side of the bridge there and look for a voltage drop. Mine got coated with melted plastic, and it was causing low voltage issues, which can cause all sorts of weird gremlins. Clean the snot out of the bridge connection (just a couple of nuts) really well if you have a voltage drop and see if you can do some good there.

After all this do a hard reset by removing negative battery cable and touching it to the positive cable for a several seconds.

See what that gets 'ya. Just my $.02. You may have bigger issues, but that is where I'd start, (and have before).

 

Cybercg, kp98xj8 --- thank you for the input. Had to make a run from the desert to town to sit the Grandies (50 miles, usually done 3x week) -- it only happened once coming in, so I know the fiddling and cleaning I did yesterday wasn't the fix. Off sitting duty tomorrow so I'll go to work on those items you mentioned then. Because of arm and hand issues, I'm not the best with a wrench these days....

Would a failing security module also cause the problem? Oh yes, the rear light fail only happened once - not at fail time, but when I pulled into the driveway in town.

Thanks a Bunch

Ken

 

I'm not sure about the security module. I guess I've never experienced any problems with mine, so I have no experience with it. I'm sure others on here have though.

Word of caution on the brake switch. It's a real bugger to get to the way it's tucked up under there. You can probably do a "good enough" job on it in situ - - red straw on WD40 can and hold a shop rag under/around it when you spray it, or you'll drip all over you and your carpet. Try to spray the pivot points, and get inside it best you can. Even in situ, you'll have to contort yourself pretty good to get to it. Please consider this if you have some arm/wrist issues. You gotta put yourself in some pretty unnatural positions for this task.

 

Sounds very much like the common throttle body issue.

I had the same thing happen, VERY hard to diagnose unless you're lucky enough to catch it in the act with a scanner. Got a lot easier to diagnose over time, it seemed to fault more and more, and store the code more often, but early on we definitely felt like we were chasing shadows.

Cleaning the plugs sometimes helps, but the fault is actually broken tracks inside the throttle position sensor, so the only real fix is either a new unit, or the better option, talk to ASI and get it rebuilt.
Comes with a lifetime warranty, so you never have to worry about it again

 

Cautiously Optimistic. Yes, that's how I'd say I am right about now.

Spent several hours, starting at sparrow f*rt this morning working through the suggestions I'd received on this and another Jag list.

-Bulb Fail rear message -- Removed the light ***'y on both sides and cleaned the connector prongs with a fine wire brush and very fine sand paper. Also removed the bulb for the brake lights and cleaned and sanded the very dirty connector tangs.

Engine Fail Safe Mode and Stability Control Failure --
- Disconnected both leads from the battery. Sanded inside lightly.
- Loosened, removed all grounding connectors in the trunk. Used a fine wire brush and sandpaper and cleaned all surfaces, the connectors and the grounding points. Sprayed then with Electronic Spray Cleaner (Radio Shack (local, Franchise) reassembled them and cinched almost tight. Moved the connectors back and forth and then cinched tight.
- Loosened and removed, cleaned the +ve connectors and 250A fuses at the front of spare tire well. Reconnected and cinched them.

- Removed air cleaner tube (for access) and then separated each connector I was able to get to (2, down low, back of T/Body area not done) and sprayed the Cleaner into both connectors. A couple expelled out detris, assume it was desert dust, let them dry, then plugged them together / take them apart 3 or so times to maybe clean the connector area. Did every one I could find and access, including ones on the front and sides of engine (my idea, since I'm in there, why not do those also) Probably 8-9 all together.

- Loosened, removed, cleaned, reconnected the +ve main feed into the engine bay.

- Did a hard reset by connecting the +ve and -ve cables in the trunk

-Reconnected the battery leads.

Test run time --

South of town here, there's a 4 lane divided road with not much traffic in the middle of the day.
Motoring down there there was NO 'bulb failure rear' indicator messages, and none ever showed. On the open stretch, a bit over 12 miles or so, I put her thru her paces, emulating as best I could the 'normal driving patterns where I've seen the nasty messages. Tests included 0 - 90, 35-70, 45 cruising, 55 cruising, 55-80, braking on and off. stopping. starting and so forth - sort of usual country-to-city driving. Twice down and back with no electrical load other than radio playing. Twice down and back, same series of tests, with full electrical load - Lights /Hi beams /AC on full - no problems evident. - Odo showed 94 miles driven. Then home.

Not sure if the problem is fixed, but previous run(s) to town would've thrown many light failures, and anywhere from 1-5 fails.

So, as I said, I'm cautiously optimistic -- Tomorrow's 75 mile o/w run into town will be the acid test - so far, anyway. Maybe I'll report 'ah sh*t', maybe I'll report 'a bit more than cautiously optimistic'. We'll see.

Long write up I know, but I wanted to document it for archive.

Thanks so much for the info, hints, tips and BTDT's you gave.


Ken

 

Good news then! I didn't see you say you checked the connection bridge at the false firewall, though. Passenger side under the hood, bonnet, (front). It's that big black shelf next to the cowl. Mine has a little tool compartment on top. Your positive cable makes a long run through it, and it's bridged by a couple of nuts right there. Remove that big black cover and observe the cable there right up top. Pull the boots back. (See pic). If it is dirty, loose or both, your alternator isn't going to be able to output it's full voltage back to your battery.

Also, if cleaning the brake switch on the pedal sounded painful, you're correct, it is! But seriously, that little bugger has caused me many problems, much of what sounds like you're describing. It's worth a shot if you can muster it.

Sounds like your cleaning efforts paid some dividends today. I would seriously also clean the firewall bridge and brake switch though. At very least, get the firewall bridge since it's so easy to get to and test with a voltmeter.

(Apologies if you said you did get these areas, and my reading comprehension is off tonight.)

 

Kp98XJ8 -- thanks for reply --- Yes, I did that -- I called it the 'main +ve feed into engine bay...... But I still went back to my notes to confirm that, just in case. It showed a .05 volt drop, but I did it to be sure.

You understated the access issue with the brake switch . It is a bit of a bugger to contort. I saw it, removed the connector a couple of times and decided it will be a 'phase-2' item... Something to do when the son is here and can get into it. Did you do it in situ or did you take it out? From using a light and small mirror, I really couldn't see enough of the insides to be sure I can actually spray electric cleaner and lube up in there..

Aside time ---- I've spent more $$ on this car in 4 years than I did on the 2 Series 3 machines (87 XJ6, 87 Vdp) - had them both for 15 years and was more confident on the San Fran > Phoenix, San Fran >San Diego runs and back than I am in this going 75 miles to Scottsdale!

Thanks again -- appreciate your time and responses

Ken

 

Spraying WD-40 on the plunger on the brake switch cured my stability control/ failsafe issues about 2 years ago and no issues since. I did not remove the switch. I just sprayed the plunger that presses against the brake pedal

 

rocklandjag -- thank you. Going into town in an hour or so - the acid test. Then I plan to get in and under with a bright light and mirror to find the plunger into the switch. If I can contort I'll get in there and spray it; if I can't - then this weekend with the son. proress posting from me I'm sure...



Ken

 

You can check the switch contacts with a meter. The outside pair are one set, inside the other. If yo don't have probes that fit in try slipping a thin stiff piece of wire like fishing leader into the plug from the back then clipping on the wires.
Pushing on the pedal will cause one set to make and the other to open.

Based on my XK8 experience, but should be the same.

 

Yup, you sure did. Awesome. Spray that brake switch and I bet you'll be in good shape. I remember spraying mine about 4 years ago in situ, and it fixed me up for about 2 years. Then I started getting the same wacky messages again, so I took it off, took it apart, and *really" cleaned the mechanism. So 2 years later, no problems yet. *Crosses fingers*.

I'll trade my water pump and leaky thermostat tower problems for your brake switch problem! Spent waaay too much time today on it, and I still don't have it fixed. The skinny coolant bleed line that comes off the side of the expansion tank decided to start leaking after I buttoned everything back up!

Ordered a aluminum replacement tower just now, and I guess I'll bite the bullet and get a new bleed line from the dealer tomorrow.... depending on how crazy a price they're asking... We'll see... (grumble, grumble...)

 

I will trade your leaky water pump and thermostat for a broken A drum and (1) dead fuel pump


This is fun!

 

Well shut my mouth. Puts my whining into perspective...

 

Time for a status update......
Well, I did everything suggested in the way of clean, tighten, check, and so forth as outlined in the previous posts....
I've gone from Cautiously Optimistic to Pessimistically Resigned. Same problems happened on the back road runs - twice - and once on the run to town to care for the grandsons. Not much progress made really, unless you consider all the cleaning and so forth progress as it did / may have eliminated variables.

Talked to my Jag Man, and we've worked out a bit of an arrangement. Will flat-bed it up to him and leave it there, to be used as the go-fer car and misc trips by the staff for a week, to see if it happens again (it will) and see if it throws a code or two.. Then we'll figure out where to go...

A question, what else could fail intermittently and cause the Stabilty Control Failure / Engine Failsafe Mode without throwing a code? Since the CAN Bus passes through the Dash setup, could it be something in there? Could an unbalanced wheel cause it?

Thanks guys!

Ken
99 XJ8 - VdP

 

That's disappointing. I'd replace the brake light switch. I see them on Ebay for $110 - $189, new. That should eliminate it being the culprit if your old one is too far gone to be resurrected by the cleaning you've done. You might be able to source one cheaper from a wrecker yard, but it would have to be awfully cheap to take a chance on it, I would think.

I'd be leery of handing it off for a week to a garage, letting them drive it, trying to make it snafu... chances are they will, and then some. That's just me though, you may know and trust every guy that works there all your life, for all I know.

There's so many threads here of success stories fixing this issue by cleaning/replacing the brake light switch, I'd stick to my guns and take it all the way to new part to satisfy myself, before I moved on. All that, of course, is just my opinion.

One last idea, and maybe someone else knows if this could be an issue with Jags, but I'll throw it out there anyway. On my son's Cadillac (FWD), we tried to run a spare for a few days on the front that was a size smaller in diameter that the others. The Caddy didn't like it, and threw out traction control errors. Just a thought. Are all your tires the same size?

 

You sure this isn't the problem?

 

I hope he's heeding and exploring the TB issue as well. Certainly sounds like it's something you've encountered, which I have not. I just ran down the free and relatively painless things for him to check that I've personally had trouble with.

I hope he can clean the brake switch again, and it would be great if he could test it while it's out for cleaning like RJ237 suggested. A new one would be less painful and more certain though. It's just who has $100-$200 laying around? His existing one is probably going to get mucked up at some point in the near future given it's age.

Hope he finds it soon, and it's a cheap fix.

 

@ Ken, if your Jag tech catches codes post them here, interested in finding an answer but the known issues have been suggested already, and dealt with apart from the throttle. The Throttle Position Sensor could well be the culprit. How does the Maf wiring to the connector and connector look? Good nick?