I've been banging my head against this one for awhile now, the last unrepaired aspect to this once parts car. The reverse parking aid module goes into alarm mode in reverse. You can turn it back on, but as soon as it goes into reverse it defaults to alarm mode. Speaker works, I replaced the module, checked for power and ground on the thing and checks ok. I know people have had problems with individual sensors going, but none of mine are doing anything. From what I've learned on here they should be audible with your ear next to them, but all of mine are silent, which suggests a complete failure of the whole circuit.
What I want to know is if one sensor goes does the system keep providing the audible signal to the others? Does it supply this signal even when it has gone into alarm mode, or does alarm mode just shut everything down? I'm pretty good at troubleshooting, but this one has me scratching my head a bit. I have the schematic and it looks like a very simple circuit (I used to be an electronics tech) but without an oscilloscope to track waveforms, it's like looking at a black box. Power goes in, but no data out.

 

I can't say it always does but as far as I know it does always activate the other sensors if one is (or some are) bad. Yes you hear it as a sort of ticking (it's not actually an audible signal but the ticking is audible).

I suppose a bad signal other than from the sensors, including loss of comms, might inhibit the above since the module (arguably) wouldn't know what to do.

Maybe the OE diags can pick out what is wrong. If IDS would do it then a (clone) Mongoose JLR is quite cheap.

 

If nothing from any of the sensors I would look for a wiring problem in the sensor circuit.

Do you have continuity? Maybe a broken wire somewhere?

It might be worthwhile to pop the sensors out of the bumper to check for damage and connections?
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I wondered that as well, except that it knows when to activate, and knows to give out a warning and deactivate and indicate so on the off switch on the console. That sounds like it's communicating with the system.

 

This would follow if they were on a common bus, but each sensor has it's own wired pair, and odds are astronomical against every sensor having broken wires/ bad contacts. If I get much more desperate I might consider pulling the bumper but that's a last ditch effort.

 

Obtain a read from a dealer level diagnostic scanner - this will narrow it down to a code(s)

If one sensor is faulty the reverse parking aid shuts down, so you wouldn't hear any sensors "click".

Most of the time it's a faulty (or dirty) outer sensor, which can be removed (tight fit) w/o dropping the rear bumper. Get a strong LED light and bring lots of patience.

 

Damn, that's exactly what I needed to know, especially since one of the sensors had been whacked in a minor fender bender. I wish I had known that before I...

 

The reverse parking aid module IS on the communication network. The module has the DTCs (B codes) stored but dealer level diagnostic tool is required.

Guessing can work but the module already knows why it has the failure 'beep'.

One trick that you can use is to turn the key to ON (engine OFF) and put the gear selector in reverse. Walk to the back of the car and place a finger LIGHTLY on each sensor and gently move your finger in a small circle to feel the pressure 'pulses'.
A faulty sensor will NOT PULSE and that may be your problem.

Keeping a finger pressed on a sensor may not provide the sensory 'feel' required to detect the 'sonic pulses' emitted by the sensor but constantly moving the finger seems to help keep the pressure 'LIGHT' enough.

You should detect a constant 'tick-tick-tick' with a functioning sensor.
Try holding your finger 'still' and see if you stop feeling the pulse. Then move your finger again. I noticed this when the parking sensors were fitted to the S-Type and it is a quick diagnosis for failed sensors.

Too much PAINT after a repair can also cause the sensor(s) to fail.

bob gauff

 

Which is contrary to the previous post that suggests that once in fault mode the system shuts down.

And this bumper has been painted, although it surprises me that shooting paint over a sensor could kill it. Are they really that fragile?

All this is starting to seem like a pain, since I could get a wireless backup camera and LCD display for 50 bucks...

 

Too much paint (a thick layer) on the sensor will inhibit it's ability to work properly but I'm sure you can wipe paint remover across it to thin the coating or remove and repaint (lightly).

bob gauff

 

I'am having the very same problem with mine.
And yes If one sensor is faulty the reverse parking aid shuts down, so you wouldn't hear any sensors "click".
I know this because mine defaults to alarm mode but the other day it worked so I did the 'put my ear to each sensor' and I could hear each one ticking and then it defaults to alarm mode they are not ticking.

So it looks like my sensor work fine but I still can't find out what the fault is.

 

Just found this-
The overhead console switch contains a Light Emitting Diode (LED) to inform the driver of the system status:
LED ON - System Active
LED OFF - System Inactive
LED FLASHING - System Fault
The reverse parking aid is active when reverse gear is selected, unless towing (with a Jaguar approved towbar) when the system automatically switches off. If the parking aid system develops a fault the tone will sound continuously for three seconds when the ignition is switched on or when the reverse gear is selected, and the overhead console switch LED will flash.

So going by above- my led is on and I have a continuous tone so my system is working fine but maybe one of the sensors thinks something is near it???

 

Incorrect.

If the led is off when car is in reverse - the system is working.

If the light switches itself on then the system is disabled.

You can also press the button (to turn the led on) which manually disables the parking aid system.

This is the laymen's terms on how the system works on your 01 S Type anyway.

If the led is illuminated and you didn't press the button and hear a tone before the light illuminates / you have a fault.

Please, do yourself a favor and get a dealer level diagnostic read of the code(s) - "B" codes related to the parking aid system. You'll know quickly where your issue(s) are.

Just my $0.02

 

This info came from jaguar's 2005 onwards workshop manual!
But yes your right, then its working the led is off and on then a fault is found.
And my jaguar is a 2005 model anyway.

Thanks.

 

gotcha... Thanks

 

After cutting all the wires to the plug and pulling on the ends I found one that was broken (intermittent). After splicing it all back together the system doesn't even try to fire up/give alarm. I think I'm done here, which is unusual for me as I usually beat things into submission, but I found a reverse camera kit for 50 bucks with an LCD display that will fit perfectly into the space now occupied by an unused cassette holder. Sometimes better to just move on.