I have the same beep and read on my OBD reader one of the rear sensors is bad. So, searching on this forum led me to test each one to find the offending sensor.

Steps:
-on level ground move key to position 2 and apply emergency brake (do not start the car)
-move gear shift to 'R' reverse
- go to rear of car and place your ear close to each sensor
-good sensor will be making a soft clicking sound
-bad sensor is silent
Here is a link to a discussion on removing the rear bumper with pics.
rear sensor replacement

 

The link was for the Jaguar XK series sedans, and not the XJ8's. In any case, I couldn't detect any ticking at all from either of those rear parking assist sensors, and even with a mechanic's stethoscope. If anything, the rear right sensor seemed only to be partially functioning in my 2005 Jaguar XJ8L sedan while the rest of the sensors were more or less inoperative.

What I simply did was:

1. Turn key to 'On' position
2. Step on brake, and move shift lever to R
3. Proceed to the rear of the car

 

Heck, with what I got, I would have to remove every single one of those parking assist sensors, and make up some sort of a homemade test stand to (hopefully) check them out. Actually, that would have to be done first before I could order anything. In the meantime, the car would likely be down for a good week or so. I think that's the situation I'm looking at.

 

I'm still getting that beep sometimes when I put the 2005 Jaguar XJ8L into reverse. I wonder, is there a wiring diagram and/or perhaps a pin layout to the plug of the parking assist module inside the trunk? Before going through the trouble of dropping the rear bumper, I would first like to check the ohmic resistance of each of the four sensors from the pins on the parking assist module plug with an analog meter. Thanks.

 

Before I even attempt to remove the rear bumper in order to access the rear parking assist sensors on the 2005 Jaguar XJ8L, I'm first going to disconnect the ground terminal from the car battery. Next, I will disconnect the electrical plug from the parking assist module. Using my Conar Model 211 VTVM (Vacuum Tube Volt Meter), I'm going to perform a resistance check of each rear sensor from the parking assist module plug itself. In fact, I may also use my curve tracer in conjunction with the Conar Model 211 VTVM although the curve tracer may be of little value in this case. If one is going to perform a resistance check on these sensors, the important thing to remember is that an analog ohmmeter must be used as a digital ohmmeter will only provide erroneous readings.

Anyways, this should be more or less what to expect on each functional sensor:

Pins 1 & 2: 19K ohms in one direction & infinity in the other
Pins 1 & 3: Capacitor discharge in one direction only
Pins 2 & 3: Capacitor discharge in both directions

Keep in mind that the Conar Model 211 VTVM will not reflect very accurate ohmic readings, but the important thing to keep in mind here is that we're only trying to determine which of the sensors (if any) have obvious resistance variances from the rest. If no variances can be found, then there obviously would be no point at all in going through the trouble in removing the rear bumper.

Note: The curve trace shown here was between Pins 1 & 2 of a functional rear parking assist sensor.






I'm planning on performing these checks sometime next week so we'll see what happens.

 

Okay, I'm back again with an update. During the afternoon today, I have determined that the Rear RH Center Sensor on my 2005 Jaguar XJ8L is open, and therefore defective. As far as the other three rear parking assist sensors are concerned, they are perfectly functional. As you can see from the photo, I attached test probes to the corresponding wires while keeping the red probe on the RW wire throughout the tests. As you can also see from the photo at the time, I was testing the Rear RH Sensor as I had the red probe on the RW wire and the black probe on the W wire. After I was done with that test, I merely shifted the black probe onto the WR wire so as to test the Rear RH Center Sensor, and so forth.

As I mentioned previously, always disconnect the negative terminal from the battery first, and use nothing but an analog ohmmeter (preferably a VTVM as shown in the photo) when performing these tests. A good rear parking assist sensor on a 2005 Jaguar XJ8L will test ~ 19K ohm - 20K ohm in one direction, and infinity in the other.

For me, this was the only (definitive) way that I could actually determine which of the rear parking assist sensors was faulty. The hard part now would be dropping the rear bumper so as to access the Rear RH Center Sensor.

 

When I use a moving coil meter, I usually use my Micronta Multimeter vs my Lafayette VTVM.

The VTVM hasn't been fired up in a few decades. You got me wondering if mine still works??(I'll have to try the old thing out)
I like moving coil meters for testing potentiometers so you can see 'dead-spots' in the film or windings.

Good to see old technology still has a place.

 

Yes, the analog ohmmeters would be very good in testing potentiometers for dead spots, and for detecting electrical pulses as well. I'll tell you what though. For testing SCR's (Silicon Controlled Rectifiers), you would want nothing but a VTVM, and a VTVM is great for servicing the old cathode ray television sets in some instances. As far as checking these rear parking assist sensors is concerned, I could only recommend a VTVM as I'm not sure how well a solid state analog ohmmeter would perform in this particular case.

 

why all the equipment which makes this so complicated. Read my post above...it takes 5 minutes top.

 

aceler8 wrote: "why all the equipment which makes this so complicated. Read my post above...it takes 5 minutes top"



Well, perhaps with that procedure, it simply doesn't work, and is unreliable at best. I mean, I had previously tried that procedure multiple times with my 2005 Jaguar XJ8L. Using that test, the best that I could ascertain was that the rear RH parking assist sensor was likely functional, but not the rear RH center sensor. Regarding the LH parking assist sensors, it appeared that at least one of those two sensors was functional, but I never could determine which of the two was functional, or if both of them were in fact actually functional.

If I'm going to go through the time and trouble of dropping the rear bumper, I would want to be 100% certain that a defective rear parking assist sensor (which I can accurately pinpoint) is indeed causing the fault. As such, the procedure that I outlined is what I strongly recommend to others on this forum. Otherwise, one may have to resort to simply replacing all four sensors (which some forum members have done), but is that a good way to fix the problem? I mean, it surely would be an expensive way of going about it. Even then, something like that wouldn't even guarantee a successful repair as one might ultimately wind up replacing the rear parking assist module or repairing a bad ground. By the way, how would you even know if your replacement rear parking assist sensor was even good without testing it with the analog ohmmeter that I previously described?

 

As I stated previously, now for the hard part: the removal of the rear bumper.

1. The first thing that one would want to do here is to put the vehicle on ramps
2. Secondly, the T25 torx head bolt next to each of the rear tires should be broken free before anything else is done.
3. There are also four Phillips head screws on the underside of the rear bumper which didn't appear to present any trouble as far as the bumper removal is concerned

At the moment, I'm not sure what I'll do next as those two torx head bolts were pretty rusted in. Actually, so much in fact that I couldn't safely turn any of those two torx head bolts loose without compromising the integrity of the plastic. I mean, I seen bicycle fenders which were far better constructed than the flimsy plastic rear bumper on this Jaguar.

Well, for the time being, I sprayed both of those torx head bolts down pretty good again with penetrating oil so perhaps I will make another attempt to break those bolts loose in the coming days. I suppose that rusty bolts



are what to expect from Michigan's harsh winters.

 

Well, after allowing the penetrating oil to soak on those two T25 torx bolts (on the underside of the rear bumper) for a few more days, I attempted to remove those bolts today. Not too surprisingly, those two rusted bolts simply refused to budge, and I sure wasn't going to apply any excessive force as it simply wouldn't have taken much to crack the flimsy plastic rear bumper. Being that I didn't have my drill motor and drill bits handy at my parents' place today, I may drill both of those rusted T25 torx bolts out tomorrow, but I won't do anything more until I pick up a couple of stainless steel bolts in place of the original bolts.

 

I had to hacksaw the fasteners apart when I did mine years ago

and I made up some new fittings.

The other way that it can be done is to heat the area with a heat gun and pull the fastener through.

 

meirion wrote: "I had to hacksaw the fasteners apart when I did mine years ago

and I made up some new fittings.

The other way that it can be done is to heat the area with a heat gun and pull the fastener through."



Yes, hacksawing the fasteners apart may be a very good option with those torx bolts and fasteners being rusted in as they are. Perhaps everything else will go relatively smoothly regarding the rear bumper removal.

 

Today, I elected to remove the driver's side T25 torx bolt head with a cut off wheel via a pneumatic die grinder.as this seemed to be another good option. Afterwards, as it appeared that the bolt head was pretty well removed, the rear bumper still did not show any signs of separating from the holder next to the wheel. At that point, I decided to quit while I was still ahead for the day. Perhaps I will revisit this job


another day, or simply disconnect the plug from the parking assist module, and be done with it.

 

After disconnecting the ground terminal from the battery today, I removed the plug from the rear parking assist module, wrapped the plug's terminals with a layer electrical tape, and cable tied the plug to a nearby wiring harness. Afterwards, I performed a hard reboot by reattaching the ground terminal to the battery, and starting the car. There were absolutely no problems whatsoever, but that was expected.

Actually, with a plastic bumper and associated plastic structures as flimsy as what I had seen, I would simply consider a rear parking assist fault in the Jaguar XJ8's as non repairable. You know, I think that a Jaguar service technician would have told a customer the exact same thing, and would have done just what I had done today. In conclusion, I no longer have a parking assist function, but I will not encounter any more such faults either. End of story.

 

I don't currently have the opportunity to drop my front bumper to fault find my "3 second beep" fault as I am getting a code fault for the front outer, and front wiring - however - if I fit a 4 channel module, will the rear ones still work and the fault on front ones "switch off" until I get around to fixing them?

 

If it were me, I would simply try removing the plug from the parking assist module, and leave it unplugged until such time permits. Next, I would perform a hard reboot as I mentioned above. In my case, even though I had went through some trouble and expense in accurately pinpointing the faulty rear parking assist sensor, it unfortunately didn't do me a bit of good. Actually, I determined that the risk of damaging the (ultra expensive) rear bumper and other plastic structures during the process would have been too great to justify the end. In that sense, I simply determined that the rear parking assist fault was not repairable, and this was similar to what transpired when my 2005 Jaguar XJ8L still had the troublesome air suspension. Regarding the latter, the plug was simply disconnected from the air suspension module when the suspension was changed over to a far more reliable and trouble free coil/spring system.

Changing a faulty front parking assist sensor may be a different story, but I wouldn't recommend it in regards to the rear parking assist sensors.

 

Thanks - what I am trying to establish is if I fit a 4ch module will the rear ones then work, at least until I have a proper chance to sort my faulty front ones...?