Most of us have the problem so infrequently that it is impossible to duplicate ....... so taking it in for service is pointless. I recently had my 02 in for A/C work and while it was connected up to the scanner -- they checked it out ... nothing. This was at a Jaguar dealer ... both the parts manager and the master tech felt that since the tbody are being rebuilt - that would be the way to go -- if you can verify a quality rebuild.

Since you are getting this all the time -- it may be worth the money to see if you can get the codes at the time of failure.


As I said previously -- I think I have a bad spot on the TPS and when I place the throttle in that position for an extended time .. I get the "failsafe"

 

I am convinced my fail safe problems were due to to battery voltage. After I replaced the battery then accidently left the scanner on it overnight with the key in the on position, which resulted in a very dead battery.
I jumped the car and let it idle for a long time turn of the driving lights to it would better charge. Been about 50 miles or more and no failsafe and no running lights.
My guess is with the A/C and running lights on, it was just to much a drain on the electrical system, especially with a lot of short trips. I will keep you informed.
Cheers

Of course, just as I get it running great I find out it is reported stolen back in 2007. Apparently, it was found but the owner had not given the police the VIN till 4 1/2 months after reporting it stolen. During that time it was involved in a crime, towed, stored, then sold for the storage fees, which gives it a clear title. Now Safeco says it is theirs and will not take it down as stolen.
Attorney agrees it is mine. Now afraid to drive till it is taken off the stolen list.
Other than that,
Cheers

 

I meant 500 miles.
Cheers

 

Thanks so much for your continued interest in this thread. Here is an update.

I am still getting the Failsafe Engine Mode (amber) message--almost daily. It will clear eventually after switching the ignition off and on again--if the computer does a clear diagnostic test. It seemed that the error message would come more often with the cruise control light OFF (maybe coincidence) but now it does not matter--it can happen when it is on or off, but the consistent thing is always that the light will not come on when I see this awful error message. I occasionally hear clicking from the righthand glovebox area, as though relays are being triggered. Once or twice, the error message has been coincident with the wiper blades wiping as it's turned on, and a "low windshield fluid" warning.

Recap:"failsafe engine mode" is coming on intermittently with the amber warning light. Engine performance is fine.
1. The throttle body which was an issue on this model was replaced by recall prior to me buying it.
2. The throttle body has been cleaned.
3. The MAF has been cleaned, and there are absolutely no holes or cracks on any of the air intake or breather tubes. I also cleaned all the electrical points to the MAF and covered with dielectric grease.
4. I used a wire brush to clean the electrical terminals at the battery, and the right hand positive pole inside the cab on the right under the glovebox, and covered with dielectric grease.
5. I changed the brakelight switch for a new one.
6. I changed out the engine fusebox (swapped with a friend).
7. I changed out the transmission control module (swapped with a friend).

The starter is fine. The battery is new. There are no codes.

Where is this gremlin coming from? Change out the ECM next?

 

It sounds like an electrical rather than ECM based fault to me.
Can I suggest
1. If you haven't already, and at the risk of sounding like the Windows call centre, do a hard reset (remove batt earth cable, touch to batt +ve for a few seconds, reconnect)
2. If (when) that doesn't help follow Bob's advice and take the car to a Jaguar dealer to have all the codes read - most OBD readers only read engine and transmission codes.
3. Identify the ECM fuse (sorry, I can't help with which that is) and measure volts on it while you turn the ignition on to see if something happens when the failsafe mode kicks in. Even better if you can get hold of a storage scope module for a laptop and look at the waveform
4. Identify and check the earth points for the ECM and anything else you can think of - as you know there are multiple earth points in the engine compartment and a bad earth could be causing these symptoms
5. Identify the ECM relay and swap it for another the same colour. Mark both beforehand!
6. See if you can track down the relay(s) that chatter when you turn on the ignition.

 

Hi there Scottish chap,
I had a lot of problems similar to yours which were eventually traced to the through panel multiplug in the passenger footwell. The multiplug is behind the plastic panel by the passengers feet. There are about 40 wires which pass through the plug, mine was just about making contact even though it has a locking clip. It eventually failed totally and I was getting all sorts of messages including Failsafe mode. I decided to cut out the multiplug completely, I carefully cut and soldered each pair of wires, shrink wrapping each one, It took me about 5 hours. When finished I switched on and the car completed the self check with no problems and started 1st. time, this was about 2 months ago and it's been fine since.

With my multiplug there was no restistance when pushing the two halves together and it was obvious it could not be making proper electrical contact. I cannot believe that of all the thousands of XJ8's made, that mine is the only one with this problem. I cannot say that this is your problem but in my case it was.
Hope you get it sorted.

 

So I did a hard reset (heard the beep), and the failsafe engine mode problem is less frequent now...maybe once every 3-4 days, but it is still there.

I will move onto looking at the ECM and fuse.

Interestingly, I seem to have less 'power' in the low gear in sports mode from take-off compared to prior to the hard reset which I am sure restored the car to factory settings with better fuel economy. Can I get that torque back?

 

Here is a JPEG file of the ECM Relay location in the Engine Management Fuse Box:
Had wrong file - removed - will update this post later.

 

Getting warmer, I think.
What MIGHT be happening is an intermittent fault on ECM supply- relay, fuse, harness, the multiplug V8mad described- which is corrupting the ECM so you're getting frequent false alarms from (possibly) an occasional bad contact.
It's worth doing this
https://www.jaguarforums.com/forum/x...connect-74146/
Your car will relearn your bad habits, have no fear!
If you can't find a bad contact one possibility would be to feed the ECM from a 'known good' +ve supply but I'd prefer you to check with a guru before doing that.

 

It was not the multiplug, ECM or relay.

Checking codes again, I got a P1517 (parking switch). Hopefully this will help some people with failsafe engine mode warnings. The cable to the shifter was tightened and the error message went away; I was getting it up to 15 times per day and in one case had to switch off and engage the ignition 35 times to get the computer to go through the diagnostic check appropriately. I agree with others that the engine will not start with this warning.

As proof of concept, the wire was loosened and the signal was on all the time (the code also reappeared after it was cleared). If anyone else gets this warning and if you are stranded, try shifting the car into neutral and pressing the brake whilst engaging the ignition--sometimes the position of the cable will change just enough to not throw the error. The car starts and drives great now.

If it will help other people, apparently the rotary switch underneath the transmission can develop this issue and throw the failsafe engine mode warning. This is an expensive part (about $700).

Hopefully this will help some other poor soul plagued with intermittent faults like I have been. Thanks to those of you who helped me.

 

Hi Bob,
I have a problem with my 2004 Jaguar VDP as it's stuck on park and it won't crank or start. Battery is good. Car was running and I removed a relay under the hood thinking it was the suspension relay. Car shut off and would not start. Have you ever seen this problem? I would really appreciate any suggestion as I can't even get it out of the garage to take to dealer.

 

Replying to angelm
Hello, welcome to the forums.
Better to start a new thread for your problem, rather than tacking on to an old thread; more chance of a reply.
Can you identify which relay you pulled, ie which fusebox, and its position in the box.
You might be able to get the car going by doing a hard reset, ie remove the negative cable from the battery and touch it to the positive cable for 10 seconds.
Re-attach and see if the car starts.
If not, you may have blown a fuse, start by checking those in the 2 boxes under the bonnet.
Keep us informed

 

You know, all of these peripheral observations are interesting, but they are not leading to an actual diagnosis in these cases. I believe that is because there are apparently many sensor or system failures that will result in the Restricted Performance mode activation and each case can be different.
AND, there are apparently different behaviors of the car when giving this fault. For instance, my cars have always cranked and started fine, even with RP showing in the display, and at least two reponders here have reported otherwise. So, my conclusion is that their RP does not cause no start, but it is likely that the cause of the no-start is the cause of RP messge.
Anyone following this thread looking for a solution to similiar problems should read Motorcrman's post from a while ago and follow his advice. The generic OBD scanners only display the generic OBD faults. A dealer level scanner, or AutoEnginuity will poll all the modules and show their faults as well, leading to much better chance of determining the actual problem. Yes, the high end scanners are expensive, yes someone will probably charge you to scan you car, but the likelyhood of finding the actual problem without wasting time and money replacing parts that are fine will most probabkly make the scanning worthwhile.

 

A no-start usually involves an unhappy PCM and ordinary OBD tools normally report all codes the PCM has. I have an elm327, AutoEnginuity and JLR Mongoose and they report identical codes for the PCM.

Commonly there are no codes for RP or no-start.

 

AngelM, a new thread would be wise and be sure to say exactly which relay. For speed, look up what that relay does and check the electrical guide for it.

 

The problem reported here is a RP that comes and goes and sometimes causes a no -start. There are also codes reported that point to a transmisison switch problem. If you read bob's post that I referred to, he says that codes form other modules can give cluse to communication issues. I stand by that statement and recommendation.

BTW, if you use your AE to check tracking of the redundant TPS and PPS sensors in the TB, you can find the disagreement that can lead to RP, for one example. In the case in point for the Scottish Chap, I would bet the transmission module diagnostics would have pointed to the actual problem sooner. You can also scan the transmission module to find input/ output speed sensor faults that lead to RP. So, yeah, connecting whatever scanner you have to the car won't do much of anything if you don't know how to use it for diagnosis.

Also, I add my voice to the chorus that has encouraged finding the original relays involved in the relay swap dance. If that really changed the behaviour, then that means at least one relay is dodgy, and moving it moved the problem to another circuit. Relay swapping is a good troubleshooting technique, not a repair strategy. It would probably be worthwhile to return to that point in the troubleshooting procedure.

 

So Scottish Chap, you had to buy a new rotary switch ? and that cured the problem, correct ? and it was a P1517 code ? Just to clarify. Thanks.

 

Hello Fredd60, Thank you for your suggestions. I have checked all three fuse boxes and MEGA fuses in the trunk along with every ground connection and tonight I started back tracking my steps. I opened the hood to double check the relays, as I moved each relay to make sure they were seated properly I heard as if connections were being stablished when I moved the starter relay. It started right up as I was ready to give in as its bloody cold here in Chicago.