My reverse light is not working! I have searched the forum and followed advice re only one and it is LED fed by some pulsing voltage etc on passenger’s side! So I have disconnected the OG (REVERSE_LAMP_CTRL) wire at CA023/4 on the AUXILLARY JUNCTION BOX and found;

1. 0.3v DC from the module. This is here with transmission in all gears including reverse, no change engaging reverse

2. If I connect 12v +ve to wire toward reversing lamp, it works, so lamp and wiring itself is OK

I have searched the forum and the XK 2006 wiring diagram and cannot find the “source” of the REVERSE signal. From my old school experience I would expect a mechanical reverse switch mounted on the gearbox, but I guess in a more modern car there will be some logic switch associated with the gear selector?

HELP!

 

Personally I would try another bulb.
Possibly the lamp monitoring system but others have had strange seemingly non logical scenarios like this but changing the bulb has fixed the problem.

A cheap and easy thing to do.
Be careful when removing the rear light cluster with the hidden nuts and breaking the pointed end of the cluster.
There is an error in the 2006 owners manual showing the nuts. The UK version states the wrong number of nuts. There is an extra one.

Does your Japanese spec XK have the rear parking aid. I think it was standard in the UK . If so is that working.

 

Note 1 Definitions

Reversing lamp means a lamp designed to illuminate the area behind the vehicle while it is reversing and to warn other road users that the vehicle is reversing or about to reverse.

The item in question is the LED light cluster mounted on the boot/trunk lid that contains the "back up light" "reversing lamp/light" "rear parking aid" etc. so is a throw away unit if is not working and costs $$$$$$$$$$$$$$$. My cluster works if 12v is applied to the unit.

I do not have a signal coming out of the AUXILLARY JUNCTION BOX !

.

 

The reason I mentioned the parking aid is that it needs the gear box to be in reverse as well to work.

The 2006 model XK uses a reverse light bulb in the light cluster on the rear wing and not a LED on the boot cluster.

writing in capital letters is RUDE and not necessary

 

My error

my 2006 model uses the LED cluster on th3 boot lid
Although the wing cluster does have a clear bulb in the clear section.

 

It probably won't fix anything in this scenario, but have you tried a Hard Reset? That's usually for software glitches, but who knows?

 

Cee Jay,
Thanks for the tip! Tried it and still no go.
Consulted the X150 4,2 Service manual and found
AJB Control
The following lamps are controlled by the AJB:Circuit ProtectionBased on this information and my early career involving discrete component electronics, I suspect that the FET's involved are part of an IC and have been damaged by Electrostatic discharge (ESD), which would involve replacing the IC.
Does the forum has access to the information needed to take this further? such as the AJB details?
Thanks in advance

 

If you have a review camera, does it come on when you put the car in reverse?

I could not find an online electrical diagram for your car. But, here is what Chat GPt has to say about it.

That blurry-looking image at the top shows part of the reverse‑lighting circuit for a 2006 Jaguar XK8/XKR (X100)—it’s taken from a factory wiring diagram. I recommend pulling the PDF or factory service manual for full clarity, but here’s how the reverse lamp circuit works:

🔧 Reverse Light Circuit Breakdown

1. Reverse lamp switch
   – A switch mounted on the transmission/transaxle detects when you shift into Reverse.
   – It sends a signal via a green/brown wire back into the main harness.
2. Power feed
   – Power originates from a fuse in the central fuse box (hot in Run/Start).
   – It routes through a bullet connector near the dash (often shared with the choke lamp connector).
3. Wiring path
   – The hot feed travels to that connector, then a green wire runs through the tunnel to the gearbox switch.
   – The green/brown return wire carries the switched power back through the same path, then splits off to the rear reverse lamps in the trunk harness.
4. Reverse lamps ground
   – The lamps themselves are grounded to the chassis, completing the circuit when Reverse is engaged.

🛠️ Troubleshooting Tips

• Check continuity between the gearbox switch and rear lamps on the green/brown wire.
• Verify fuse & connectors, especially at the bullet connector near the dash.
• Inspect the switch on the gearbox—it can fail or get misaligned.

📘 Diagram Access

To view a clear, full diagram:

• Grab the factory service manual (under “Electrical” or “Wiring Diagrams” for XK8/XKR X100).
• You’ll see a full schematic where the reverse circuit connects: fuse → dash bullet → gearbox switch → back to lamps.

If

 

My 2008 xk had a bulb out warning for a week but all bulbs worked fine. Pulled and replaced bulbs in L rear tail light assembly (old ones looked fine), tested and warning went away. Jag electronics get really confused by values out of their designated range. If hard rest failed to help, try replacing bulbs.
wj

 

@gmuirnz , do you have the electrical guide? If not PM me.

 

Before you replace any bulbs, swap them. That'll tell you if it's the bulb or the light assembly that's bad.

 

The LED clusters that've failed not an individual incandescent lamp.

 

If anyone knows what this voltage should be, maybe that would be of some help. If it's a matrix signal or whatever a weird signal is called nowadays, it may not show up correctly on a multimeter. I'd expect 12 VDC myself, since the cluster works and such. Is or is not the 4.2 reverse lamp incandescent? I don't know the answer. If LED, it could be something crazy.

 

The schematic seems pretty straight forward. Yes, its LED.

Hope this helps.

 

Thanks for all the feedback & advice. I have extracted the following (and modified in RED) from the vatrious docs and is my now understanding of how it works>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
PRINCIPLES OF OPERATION REVERSING LAMP

Selector Lever
The selector lever is located in a slot in the rotary disc which rotates with movement of the
lever in the forward or back directions. The disc movement positions magnets located on the
disc which are detected by Hall sensors located on the selector PCB which correspond with
the different selector positions. The Hall sensors produce a signal relative to the lever position
which is passed as a high-speed CAN bus message to (the TCM and on to) other system modules (including AJB)
Reversing Lamp
The reversing lamp is located in the inner rear lamp assembly. The reversing lamp uses 3 LED (light
emitting diode). Only one reversing lamp is fitted and is located in the LH (left-hand) inner lamp
assembly on RHD (right-hand drive) vehicles (mine)and in the RH (right-hand) inner lamp assembly on LHD
(left-hand drive) vehicles.
The reversing lamp is activated on receipt of reverse selected message sent on the medium speed
CAN signal from the TCM (transmission control module) to the AJB.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Still to find out what the output from AJB to LED actually is! Now if I had access to an old school ossiliscope I might be able to do that.

I found another thread about similar problem with the LED High Level Stop Light and it appears that the solution was a hard reset by disconnecting both battery leads, touching them together, then waiting 30 minutes before reassembly, TWICE! So I will try that tommorrow
Thanks to you all