Help needed, please. My 2006 4.2 S-Type has both front and rear obstruction sensors. The front units work properly. But when the car is put into reverse, the rear sensors trigger continuous sounding whether there is an obstruction or not. There is no intermittent beeping, just the consistent and constant (and annoying) alarm
It can be cancelled by pressing the button on the roof console, but that only makes it temporarily silent. The sensor surfaces are clean and dry.

Where might the problem lie? Grateful for any suggestions.

 

Leave it making that din and listen very close to each of the sensors - if they're working each makes a quiet ticking.

Or - better - get a code reader that knows the Jag modules and see what codes there are.

 

A known fault with these is that water can get into the parking sensor control module in the boot/trunk. Check the arae around the box and its connector first for signs of water ingress before looking into a faulty sensor.

On the later facelift cars, like my one, the sensors did not make any noise that I could detect so that may not work on your 2006 car, but it is worth a try

If that does not work then there are two ways of identifying a single faulty sensor:
1. Purchase one new replacement sensor (valeo is the make to go for as they are OEM and some cheap ones do not work at all!!). Next take the bumper cover off resting it on a platform of some kind without obstructing the sensors and so that the sensor wires are still connected. Using your new sensor plug this into each connector one at a time again so it is not obstructed. Test each one by selecting reverse to see if the fault goes away, when you find a location where the fault has gone change the sensor.

2. Use the Jaguar SDD software to tell you what sensor is faulty, it will tell you 'LH inner' etc. Then take the bumper cover off and replace that faulty sensor.

The hard part is getting the bumper cover off as you may well find that the fixing bolts that do not go into the main body have rusted solid. It is way quicker to carfully grind off the bolt heads using an angle grinder than it is trying to free them. When putting it back together use all new stainless steel bolts and stainless steel captive nuts so it comes apart easy next time.

 

An iCarsoft Jaguar specific code reader will also pinpoint a duff sensor or failed module. My LR-ii does and the i-930 should as well.

 

One thought: A continuously triggered sensor may not necessarily be logged as a fault. Not sure how "smart" the computer is, but it may not think anything is amiss. For example, if you backed into a parking spot up against something, it would be perfectly normal for a sensor to say, "I'm up against an obstacle". Depending on the obstacle, it might be anything from 1 to 4 sensors detecting proximity. When in reverse, the speaker would sound. When placed in any other gear before moving forward, the speaker would be silent but the sensor(s) would continue to quietly report, "Nothing has changed and I'm still up against the same obstacle". But then again, maybe the computer is really smart and is able to flag a sensor continuously reporting an obstacle while moving forward. Hard to say...

My experience with a bad sensor on my '02, but it was a different scenario. The sensor was dead and not clicking, where your sensor appears to be still be active, but some of the details may still be of interest:

https://www.jaguarforums.com/forum/s...cement-269327/

 

Thanks to those who have answered. I might not have made the issue clear. The problem is not that the sensors are NOT working. The problem is that the sensor(s) are sounding their STOP! message constantly in R as though the car were within an inch of an obstruction.
I will check for water in the trunk but I have seen no evidence of this so far. Not sure where that module is though. And I will use my BlueDriver OBDII reader to see if any code comes up.

All help gratefully received. Our 2002 X-Type has the same issue occasionally but always in winter conditions when the sensors may have a film of frost or ice. That is not the case with the S-Type.

 

A conversation with my JLR dealer’s service people today supports the advice given here, that is that if one of the sensors is bad/inoperative the system switches to the constant (irritating) warning sound.
There is no moisture at all in the trunk area. So I will check for a failed sensor. Many thanks for this advice.

 

If you're lucky the bad one will not be ticking.

 

No, we gotcha. Your original post described the situation very well. The more common failure, which some of us have experienced, is a sensor goes dead and doesn't report anything to the controller. For this scenario, the controller basically shuts off the system and gives you a red warning light and single short tone to say it's not working.

Your situation is just the opposite and fairly rare, with a suspect sensor continuously saying it's in proximity to an obstacle. Please see my previous bloviating (I'm invariably one to eschew obfuscation) on my theory of the controller not considering this as a fault. It is certainly possible to already be next to an obstacle when you initially shift into reverse.

Because you have the rare condition, we don't have a lot of specific troubleshooting tips to offer. You have to kinda sorta extrapolate from what works when troubleshooting the common fault condition. As previously suggested, I think you may have to try a known-good sensor at each location. I don't think you can just unplug each one individually as a test. The controller would think that's the common scenario of a dead sensor and respond accordingly, and you'd have no way of knowing if the sensor you just unplugged was good or bad. I'm pretty sure you'd have to try a good sensor at each location to find the bad one.

Please keep us posted with what you do find, and if there are any troubleshooting shortcuts you may discover.

 

I had this on X-Type 2.5L. My solution was to pull the power supply plug to the parking sensor module in the trunk...: That'll teach the beeper to shut up!

 

It may be a while before I sort this out but I will report on what I find. Meanwhile the cancel button on the roof console works just fine ☺️

 

Well, I might have solved the problem of the constant sounding of the rear sensors, but a definitive answer will have to wait a bit. I watched several you-tube videos about this issue which suggested that a close spraying of WD40 on the sensors can fix the issue (which has existed for months).

Sure…and I have an ocean-front property in Saskatchewan that you might want to buy…ah well, what do I have to lose other than a few minutes time? So today in my garage I sprayed the rear bumper sensors at very close range, wiping the excess away immediately, and some time later I repeated the process.

Started the engine, put the car in R and the beeping was intermittent as it should be, given that the bumper was about three feet from the (closed) garage door. Moved the car closer to the door and the beeping became a constant (irritating) noise…I was unable to verify further because it was raining today…Doug, are you reading this? 😄 The S-Type has just been detailed and waxed so no wet road travel in its immediate future. Yes, I am eccentric.

But can spraying WD40 on (and therefore possibly into) the sensors really have worked??? Stayed tuned. I will report further once I have tested more thoroughly. If it did work then this is the fastest and easiest repair I have ever found.

 

Hi Gregory,

Did you find the WD 40 worked? I have a failed left inner sensor that I diagnosed with the clicking noise hearing test. I did try the WD40 procedure, but it didn't work for me. Maybe I should try it a few more times? I would be nice to fix the annoying warning every time reverse is selected.

Thanks for any help.

 

To my great disappointment, the WD40 trick did not work. But then, trick solutions involving that product rarely work…so here we are a couple of years later with the constant noise of the rear sensor system still an issue. I have developed a reflexive habit of just pressing the cancel button on the roof console. That DOES work perfectly.
The awkwardness of access to the sensors on the S-Type discourages further investigation.

 

Thanks Gregory. It did sound too good to be true to be honest. At least I have found the guilty sensor and good used ones are easy to find. But, as you say access is a challenge as it looks like it is a bumper cover off repair. I have read that some people have found success by simply removing the on-side tail light and accessing it from there. I might give that a go. Also, I'm not sure I have a cancel button on the roof. I'll have a look. That might only be fitted to cars that have the forward park assist. Mine is rear only. Thanks again for your response.