Parking Sensors

[Martin904]

I am getting a constant tone from the front speakers and the red LED is on in the switch whenever the speed drops below approx 10mph - any ideas ?
I know these cars do strange things when the battery gets old and the voltage drops, could this be the cause ?

[barrywi]

If the car is moving the alternator should provide enough volts to avoid problems with the sensors. If you put your ear next to the sensor with the engine running you should hear clicks which will tell you if the sensors are ok. Unlikely that all four would go faulty at once so could also be a fault in the system that controls them. Try cleaning them carefully with a small brush in case they have been coated in dirt.
Another thing to try is disconnecting your battery for ten minutes or so ( make sure you have the radio code to re set it) to see if that clears the fault and maybe have the battery tested anyway, usually free at tyre centres.
If you only do short trips the battery gets a hammering at this time of the year.
Let us know of the results of doing these things.

[Martin904]

Can anybody tell me where the parking sensor control module is located. i am told sometimes the fault can be a loose/dirty plug connection.

[jeff1954]

On the SType the rear parking sensor module is in the boot.

Jeff.

[ptjs1]

Martin904,

If you have the parking led light coming on at under 10mph, then that indicates a fault in the front sensor circuits.

I would start by checking if all 4 front sensors are polling. With the ignition on but without the engine running, put the car in Drive and make sure its securely chocked and handbrake on. Listen (very) carefully to each sensor. You will hear a rapid ticking noise. If any are not ticking, then that sensor or circuit is faulty. You will appreciate that if one sensor is faulty, the system defaults to "not working" as it can't accurately resolve the situation.

The problem with X-350s is that it is just about impossible to get to the parking sensor loom connections until you drop the front bumper. One of two of the sensors are just about reachable (with skinned knuckles!) whilst the bumper is in situ, but I've never been able to remove the wiring connectors. Give it a try - you might have even slimmer hands than me!

The main module is in the spare wheel well at the rear of the well. You might want to check the integrity of the plug connection, but my guess would be that the problem lies more likely with one of the front sensors or wiring connectors. You can get the bumper off in 30 mins but try and enlist the help of a friend to avoid damaging paintwork.

Good luck

Paul

[J44EAG]

As an additional and I hope handy general offering on the subject of sensors, this is my experience to add to the discussion.

I`ve had a sensor module in an S-type suffer from galvanic corrosion and cause manic beeping and malfunctioning of the warning system. Perhaps a similar problem may occur on a 350.

Upon examining the module, I noted dampness on the case. (The S-type is prone to standing water in the spare wheel well which can find its way onto the module case and wreck the internal electronics pc board) The module is mounted low down in the boot and is an easy target for any sloshing water or dampness. It is possible to prise back locking tabs on the case and remove the pc board for inspection. On the module I examined, part of the board was covered in crystalic copper sulphate grunge. I cleaned up the mess and plugged the module back onto the car wiring loom. To my astonishment normal service resumed. I then drilled a 6mm hole at the lowest point in the boot well panel to ensure that water could never build up and flood electronic circuits, cable runs or connector plugs.

On another car, I was not so lucky and the module had to be replaced. Many different versions of a module get built into cars dependent on specification and model year or get modified during a production run. It is essential to replace like with like as regards part numbers. I`ve known an incorrect part not to work for obvious reasons.

Getting to the sensor plugs can be a real cuss. Barry will remember I had a dodgy sensor at Southern Day last year which stopped ticking. Ian from XJK managed to get his arm behind the bumper and wriggle the connector which instantly cured the problem. Bearing in mind the nasty conditions in which a sensor operates, it is not surprising that the occasional resistance spot builds up and the sensor stops working. The sensor plug once moved or if required cleaned up, frequently gets things going again. Irritating if the bumper has to be removed, but as Paul says, that is sometimes the only option.

Mike

[ptjs1]

Martin904,

This is naturally about your X-350 and the accessibility and exposure of the sensors is very different to other models. As Mike knows, I was easily able to access his rear S-type sensors at Beaulieu with my hand, the corollary being that it is also easier for water and crud to get to them. The X-350 sensors are very different, the location of the bumper cover precluding normal water ingress but making access from below just about impossible.

Good luck with resolving the problem.

Paul