Our 2000 XKR has started providing a “Failsafe Engine Mode” alert after about 7 or 8 miles of driving. I’m trying to figure out what this likely means. From a little bit of searching it looks like this might be related to the water pump for the intercoolers? The engine seems to make full power and has no issues.
What’s also interesting is that at the same time it also puts up a “Check Rear Lights” alert. I checked the rear lights (including brakes) this morning before I left for work and they all worked just fine. The fact that this turns on concurrently with the other warning makes me think this is erroneous.
I haven’t tried to pull any codes off of this. There’s no check engine light that comes on, and what’s interesting is that the code resets every time I start the car. So for example at lunch I ran an errand. The dash was clean, no codes on either running to the store or running back to the office. I am sure it will come on on the drive home again.
It’s been a while since I’ve dealt with these, but I seem to recall a check engine light for DTCs.
When the check rear lights warning comes on have you stopped the car but left the engine running and looked at the rear lights? They might be showing the brake lights.
Good thought, I’ll take a look at the batteries. I don’t know how old the battery is on this car. It has always started just fine since we bought the car (about 3 months ago now) but on these computerized cars things can be weird.
A couple of other notes:
When the Failsafe Engine Mode and Check Rear Lights indications come on, the cruise control stops working. The indicator light by the shifter goes off and it won’t work
It’s been cold (below freezing) every time I drove it with these lights on until today. Today it was in the mid 50s (F, not C… so figure about 12-15C) and today I really noticed it being down on power from a stoplight. This makes me think the electric water pump for the intercoolers isn’t working
My first question: What exactly does “FAILSAFE ENGINE MODE” mean? I’m not getting a check engine light with this. Would it still throw a DTC?
Can this be triggered by an inop intercooler electric water pump (which I know are common failures) or, if this is triggered, will it turn off that intercooler electric water pump on its own?
And yes, when the “Check Rear Lights” is on (keep in mind: these ALWAYS go on together) I’ve confirmed all the rear lights work. So that also makes me wonder if there’s a computer/module that’s going out that somehow controls both those items (the rear light diagnostics and the electric water pump).
Check the brake light switch, this has 2 contacts, sometimes the CC switch fails open which is what cuts the CC when you hit the brakes. I had that happen on my XJR and I cleaned up the micro switch and it stopped throwing the warning, I don’t recall it throwing a code for that as it is just a micro switch.
My experience with failsafe mode. This is just some insight and possible cause! Sometimes you won’t get a check engine light. But you will have a code it has come from experience believe me! It’s coming from a sensor or thus a electrical issue. Normally when this happens in my occasions is the TPS. SOMETIMES it won’t do it for miles and miles then somedays it becomes a newsonze…constantly on short drives and the cruise control quite it’s part of that system failsafe protect mode! Do not spend 1500 dollars replacing TB it’s something less expensive and if your doing it yourself you can save your self a few quid for beer after the repairs. Has for brake light this is also common on ours normally the lower side light on rear right. A bad bulb connection. You can buy used TPS at some places but finding a xkr at picknpull is few and far between. You can also test TPS with scan tool it will give you range on the cheapys. You will have one code which stays there that means the system is ok. Good luck mate
It is true that the “failsafe engine mode” warning is often triggered by a bad throttle position sensor, but when that happens it is accompanied by a massive reduction in engine power - like running on just 2 cylinders instead of 8. It can be almost dangerous if it happens on the freeway. The original poster isn’t experiencing any power loss as far as I know.
If it were the TPS, it can be rebuilt for $400. I had that done and it worked beautifully.
The cruise control can’t be used when the failsafe comes up. So I’ll look at the brake switch. I do know that the brake lights are working - the 3rd brake light is a bit loose so we can see that it always illuminations. But that would also make sense for the “check rear lights”.
The switch that is operated when you press the brake pedal has two separate sets of contacts. One set is dedicated to the cruise control circuit and is in a circuit that provides an input to the ECM. The second set of contacts operates the brake lights but also provides a (different) input to the ECM. I suppose this will relate to ignition timing and engine overrun.
This means that it is perfectly possible for the brake lights to function in the presence of a fault with the other set of contacts. The Electrical guide differentiates between the sets calling the contacts in the cruise circuit the Brake Cancel Switch.
Is this related to the Failsafe warning? Well, I suppose it could be if the ECM is smart enough to detect that the two sets of contacts are not in sync. The circuit shows the cancel switch as normally closed and the brake light switch as normally open which is as you would expect. This may be extrapolating a theory too far but maybe if the cancel switch circuit goes open when it shouldn’t, the ECM detects this and puts up the alarm. It would be possible to test this but you would have to physically break the cancel circuit somehow. You can’t just pull the plug because it’s a four pin connector. that does both switches.
Maybe simpler to replace the switch and see if the fault goes away. It’s an awkward little sod to get to.
Thanks Eric. That does sound like a potential culprit. It would also explain the dual failure (so to speak) that I’m seeing.
I’ve been procrastinating ordering a new rear view mirror from SNG for a while and it sounds like I should just order this switch as well and replace it.
Remember, it’s only a possibility based on a few observations. Depending on the price of the switch, it might be worth investigating more before spending much money.
I would try cleaning the switch first, they are not inexpensive little suckers! It worked for me because I purchased a second hand item that is sitting in my toolbox in the garage!
Apologies for the cross-posting but I saw this on the XJR forum and replied to it there.
I had this problem on two year 2000 X308 XJRs, and in both cases it was the Brake Pedal Position (BPP) Switch. The BPP switch contains two microswitches, one for the brake lights and the other for the cruise control. In a thread on another forum I saw someone say their nylon quadrant had worn, and they’d glued a piece of credit card onto it to compensate. In one of my cases that was exactly it. I only had to depress the brake pedal a tiny amount, and I could hear the microswitches click. I glued a piece of credit card onto the nylon quadrant and that sorted the problem.
In the other case the C/C microswitch was dicky. I was able to get contact cleaner into the C/C microswitch and get it working again. As a precaution I glued a piece of credit card onto the nylon quadrant and was glad I did when I realised just how little the pedal needed to be moved to de-activate the C/C.
If the microswitch is totally U/S, it ought to be possible to replace just the microswitch with careful soldering, at a fraction of the price of a new BPP switch.
As an aside, although the BPP Switch is held on by just one bolt and a self-locking nut, it’s a bear of a job because you’re upside-down with your head in the foot well. Because the bolt is long, it’s a real pain running the nut off. I had no ratchet small enough to get in there. I was dead lucky finding a rubber bush which was a lovely tight fit on my ¼" drive socket, giving my fingers much more purchase, and the resulting tool made it a breeze to spin the nut off the bolt (and later back on again). I have photos of the disassembled switch if they’d be of use to anyone.
I might add that I don’t know why the Failsafe Engine Mode is caused by problems with the C/C switch, but they’re definitely linked. The first time I ever saw it, I’d tried to use the C/C and it wouldn’t work. Only after I’d tried engaging the C/C several times did the Failsafe Engine Mode appear. Whenever I’ve had the Failsafe Engine Mode, the C/C has been disabled, and the light on the centre console has gone out.
