Ok since Sunday, I have had 3 instances of an amber Failsafe Engine Mode message.

The first instance I was on my way to get gas and a block from the station I got the alert, no noticeable drop in power but did notice Cruise Control lite went out. pulled up to a pump, read codes - none (other than 1111)
turned car off, filled up restarted and alert was gone.

Yesterday afternoon and again this morning, it came on and cruise control lite went off - again read codes both times and only my spurious P0171/174 lean banks 1&2. Turned car off waited about 30 seconds, restarted and alert gone.

Thoughts???? Aside from ABS codes are there other codes that cannot be read with the Torque Pro app and bluetooth adapter?

 

My experience is with the 1999 XK8. That being said, I read on here somewhere that the failsafe engine mode light coupled with the cruise control light going off and therefore the cruise control will not operate, has to do with the cruise control connection points at the carburetor. The advice I read was to turn off the cruise control and leave it off unless you decide that you wish to use it. I guess constant power to the cruise control is best not done as it can/will trip the control module into failsafe mode.
I followed the advice and switched the power to the cruise control off at the console and switch it on when I want to use it, thereby not supplying constant power to the connection points.


I've had no warnings of failsafe mode ever since and the cruise control works fine.

 

I had a similar problem it turned out to be the brake pedal switch. which is an easy fix. it is located under the brake pedal. hope this helps

 

typically the cruise is always in use as most of my driving is highway - will look at connection points as well as brake switch

kind of surprised there are no codes showing as the dtc chart shows code for the brake switch, cruise....

 

The brake switch does not normally produce a P0171/0174 code. I would be looking for a vacuum leakwith the codes you have. Yes Jaguar has propriatory codes that Torque and other readers can not see.

 

I just went through the same experience, same codes. Turned out my air intake bellows was cracked. Some black duct tape and good as new, almost. At least no more codes or reduced performance warnings.

 

Steve,

An intermittent failsafe which clears on a restart can be one of the early signs of a failing battery.

Graham

 

Why "spurious P0171/174"? Normally they're for serious fault!

 

Thanks guys

The intake bellows is new (replaced about 8 months ago) no damage, battery is a year old.

The Restricted performance message shows for about 5 seconds then goes away, no CEL, I checked codes and show the 171/174. The codes were reset when I had tranny work done and took almost 4 months before I got the 171/174 to show again. along with another tranny code that required rework. Once again they reset codes and it has been a few weeks since but when I got the Failsafe Engine Mode, I checked codes before I shut her down and had the 171/174. I shut the car off and restarted, checked codes again and no codes - thus my referral as spurious.

Looking at the intake, it appears the gasket between the MAF and intake tube is missing which has been ordered. I replaced the intake last year but there was no gasket at the MAF only at the throttle body. Hopefully that will clear the 171/174

 

See if this procedure helps

Link http://www.jagrepair.com/images/Auto...otos/P0171.pdf

I use throttle body cleaner when spraying around to find leaks however, the smoke test is the way to go.

 

All of the suggestions have so far been worth investigating but there's one that's missing.

When I first got my '99 XK8 with 57,000 miles on it AI had to drive it home some 250 miles. About half way I got the amber light and restricted performance message which in my case limited engine RPMs to no more than 3000 which was probably something close to 100mph as 21-2200 is 70mph.

I didn't have a clue at the time and obviously couldn't read any codes at 11;00 pm on the interstate to I pressed on. It was however somewhat intermittent and never made the dreaded RED light.

To make a long story short after checking in to the forum and reading the various suggestions as well as the service manual and JTIS I decided to first give the MAF sensor a thorough cleaning. I had no intake leaks, the bellows and seals were all good, so I took a shot at the MAFS. It took me two attempts to get it really cleaned as my first try was unsuccessful.

The second attempt and BINGO no more amber light and restricted performance as a result of those particular codes.


I'm now dealing with a misfire / bad coil on #6 but am hopeful that anew coil will cure that problem as well.

 

With the fact you had transmission work done and if they had to pull the trans out I would suggest checking around the throttle body area. The area is tight for the transmission bolts and you have a good chance in coming in contact with the vacuum lines. Do you know if they pulled the throttle body off the car?

 

Gus thanks for the link was going to hit your site this weekend while I'm looking around. as for the question on removal of the throttle body - I don't know what all they did when they removed the tranny, but the throttle body was removed about 3 weeks ago to replace the 3way connector so I will check to make sure nothing was disturbed/damaged

RD - thanks I did clean the MAF a while back - which is when I found the intake tube was failing so will try that again as well.

 

When they R&R my trans they broke a 02 sensor plug and 2 vacuum lines. Check it out chances are your problem is related to the work done. However, do not limit your search to that area. My vacuum leak is on my page and still working on it.

 

well I do know they broke one of the O2 sensors and replaced on their dime - soooooo..............

 

YOU check the plugs! Check it all!

 

Gus - will do and many thanks!!!!!

 

I had this problem with my '01 XK8. My problem was the throttle position sensor which is built onto/into the throttle body. Luckily Denso makes one that can be installed onto the throttle body eliminating the need (and cost) of replacing the entire throttle body assembly...

 

Lean on both banks is the problem, usually a failed MAF sensor, or vacuum line/o-ring leak that goes into the throttle body through the inner fender well.


Also check the ground strap that goes to the tranny bolt to the frame on the passenger front side


Then your negative cable strap in the trunk , if either has a little greenish tint/ color,a little crack, or a little whitish color, there is your solution.Battery age don't mean anything, have it checked as well, these cars hate marginal batteries

 

Can I ask where you purchased the Denso throttle position sensor?