Hi all,

I’m dealing with a persistent adaptive headlight fault on my 2007 Jaguar XKR. The issue began immediately after attempting to start the car on a completely expired battery (only putting out around 10–11V). I've since installed a new battery, and all other fault codes (including airbag, etc.) have been successfully cleared.

However, the adaptive headlight fault remains, and I’m getting the following permanent DTC:
U3000-49 – Control Module: Internal Electronic Failure
I understand this is a fairly generic code that applies to various modules, but given the flashing adaptive headlamp warning and behavior, I’m assuming it refers specifically to the headlamp control module.

Current Diagnostic Info:

• Supply voltage to the headlamp control module: 12.3V
  
• Front/Rear axle leveling sensors: Reading between 40%–50% and responding appropriately to vehicle movement (i.e., rocking the car)
  
• Leveling Target Step: Stays at 0 — I believe this value only changes during active commands or calibration
  

Behavior After Clearing the Code:

If I clear the fault (via OBD2 tool or by disconnecting the battery), the headlights attempt a self-test:

• Both lamps swing inward, hit a physical stop (accompanied by a short “motor-bottoming” sound), then drift back to a dipped forward position.
  
• Immediately after, the flashing adaptive headlamp fault returns.
  

Attempted Calibration:

When trying to run:
Service → LAP (Head Lamp) → Adaptive Front Lighting System → Headlamp and Axle Sensor Calibration
I’m met with a "Communications Failure – Application Failed" message.

My Questions:

• Could the low battery or a voltage spike during cranking have damaged the headlamp control module?
  
• Or is it possible the headlights are stuck in a fault loop, needing a higher-level diagnostic tool (like JLR SDD or Autel, etc.) to complete a full reset or force a recalibration?
  
• Has anyone encountered this issue before? Any advice or insight would be greatly appreciated — especially if you’ve dealt with headlamp electronics on the X150 platform.
  

I’ve attached photos and a short video clip of the scan tool in use and the headlight behavior for reference.

Thanks in advance!
—Tom

















U3000-49 Permenant Control Module Fault

Battery Test Readings

Lap (Head Lamp)

Adaptive Front Lighting System

Communication Failure, Application Failed

Part Numbers

 

 

A common problem with the older XK's is corrosion on the ground lug on the right side chassis which gives the adaptive headlight fault - it may be worth a check, mine was intermittent, would appear then go away for weeks. I removed the wheel, saw that there was corrosion around the lug, tried to remove the nut and the whole thing fell apart - end up drilling and tapping a hole and reconnected the lugs.

 

Thank you for the reply. This is something I have heard of, but haven't checked since the issue only arose after the battery fault.
My car also has 42k miles and is a Japanese import, so it should be very rust-free. But I will take a look, thank you.

 

And 12.3 v is inadequate.

 

This is voltage when the car is in pre / aux and the engine isn't running. It was displayed when viewing the modules data through my ICarSoft JLR V3 - OBD tool. Please could elaborate on what the voltage should be then and how to access the module to get a more accurate reading with my multimeter.

Please see attached

 

Should be a minimum of 12.6 volts. Module service and diagnostics should only be done whilst the car is connected to an external regulated power supply. Not doing so could potentially damage modules should power fall below the minimum threshold.

 

Thank you for the reply and actually telling me the expected voltage. Could this under voltage at the module be a sign that the module has failed then? If the modules are able to be damaged below the threshold then a low voltage startup could have definitely damaged mine. How can I confirm my module is definitely broken or is It stuck in some calibration fault loop? Or how can I diagnose my problem further?

 

Your battery is not supplying the correct voltage.
There are many, many references on this.
May I propose,
1. Disconnect the battery.
2. Fully charge the battery. Then disconnect the charger.
3. WAIT 24 hours.
4. Take a voltage reading.

If the voltage reads 12.6v or slightly higher, your battery is good.
If the battery reads 12.4v or less, it needs replacement.
Note, 12.5v is the grey zone. Some continue with this. Some don't.

As Jahummer suggested, the workshop manual clearly states "connect a charger" nearly whenever working on the car.
Coincidentally, "faults" magically disappear once a correct voltage is supplied.
Cheers.

 

Thanks for the reply, but just to be clear — the battery is a brand-new Yuasa, manufactured this year and had been fully charged. The car hadn’t been running, so obviously it wasn’t getting alternator voltage, and it had simply been parked for a day. The issue existed before that and hasn't changed since. So the new battery isn’t the problem, nor is the voltage state.

What I’m actually trying to find out is:

• Has anyone seen a control module behave like this after being exposed to low voltage startup?
  
• And if so, did it require a replacement or a recalibration from Jaguar using SDD/Pathfinder?
  

If there's genuine technical insight to share, I’d appreciate it. Repeating battery basics doesn’t really help does it? Vague mentions of "many, many references" don't mean much without links or specifics.

On that note, if you do have access to the correct workshop manual, please share it. The MediaFire links on the forum are dead, and the only references I can find about chargers relate to the supercharger or generic pre-work disconnect steps — nothing module-specific.

Cheers.

 

@Garron Here's a link which might be helpful. https://www.jaginfo.org/threads/what...t-unit.116643/ A regulated mains power supply (NOT a charger) is something all main dealers and competent independents use anytime performing module service. A battery or charger's not sufficient to provide proper constant regulated power to the vehicle whilst in service.

A new battery doesn't necessarily mean it's in good order or at the correct voltage, so regardless of anything else, I'd at least verify it's capacity and voltage. Bad batteries and canbus voltage irregularities can induce MILs and DTCs in modules which new batteries don't always automatically resolve.

As for the adaptive headlamps and modules, there are individual ones on each headlamp, plus the adaptive module and the headlamp ECU. There's also issues with the headlamp internal wiring where insulation's been failing and causing shorts. Early X150s have also seen these modules fail and require replacement.

 

Multiple modules will error out due to under voltage. I don't have any direct experience with your particular module but it is always the first test in diagnosing any electrical error code. Do you have the correct voltage to the module?

 

There is a root cause analysis (trouble shooting procedure) in the workshop manual...

As suggested by a few senior members (who want to be helpful) have suggested, pinpoint test 1 has not been completed.

best of luck.

 

Firstly, thank you all for your continued support — it’s genuinely appreciated. If I came across as dismissive earlier, that wasn’t my intention at all. I think it was a mix of misunderstanding and my ignorance coming from an electrical background. So I do apologise if it seemed like I wasn’t taking your suggestions seriously.

I had assumed that since I drive the car regularly — often on long dual carriageway trips sitting at 70mph for a couple of hours — that would be more than sufficient to keep the battery in a healthy state. In my mind, that felt like a good representation of real-world battery performance, so if a fault wasn’t clearing under those conditions, I didn’t think voltage would be the cause.

Now I understand what you’re saying: Even though the battery is new, the car can be especially picky with voltage levels, and “new” doesn’t always mean “full optimal charge.” It makes sense that if the battery has been in transit, it might not meet the narrow thresholds the car expects — and the system won’t restore itself unless that voltage is absolutely spot on. That clears up a lot for me.

To give some numbers, I tested the battery using my calibrated tools I use for work — a multimeter and a load-simulating battery tester — rather than relying on the OBD port. This was after a 130-mile journey with plenty of steady driving at 70mph. The battery is showing 12.79V and 89.75Ah, just 0.25Ah under its rated 90Ah (See attached). So, according to @guy 's helpful reference:

“If the voltage reads 12.6v or slightly higher, your battery is good…”
…it seems the battery is in very good condition.

@jahummer — I’ve taken your suggestion on board and plan to get a , then adjust the varistor until I see 13.5V on the multimeter. From there, I’ll connect it in parallel with the battery and re-run diagnostics. Just to confirm — That is the correct equipment stated in the previous thread you listed? The idea being, with the correct voltage present, the module will allow communication or fault clearing, right?

The only reason I was unsure is that the airbag module — which I always assumed would be one of the most voltage-sensitive — cleared fine without issue. But if this has worked for others in similar situations, I’m happy to try it.

Lastly, even though the car is used often and not just for summer weekends, I do think it would be a good idea to keep it topped up at home. I’m considering a CTEK MXS 5.0 — do you think that’s a good choice? Or is there something else you’d recommend, including best practices for how to leave it connected?

Thanks again for everyone’s input — it really helps.

(Please can someone attach a 2007 XKR Workshop manual PDF) - Mine doesn't seem to reference these procedures you're mentioning, and the Mediafire download links on this forum no longer work.


Battery Amp Hours Under Simulated Stress

Battery Voltage Under Simulated Stress

Battery Voltage

 

@Garron
I’ll leave the code reading to the experts.
with regards to the CTEK, there is a nice Brit on YouTube (Life on cars?) who has an episode where he shows how to permanently install the CTEK add on permanent hardwire kit so they stay in the trunk.
Then he mounted the CTEK on the wall with the extension cables to plug in when the car is garaged.
(I plan to do this)

There were a few different approaches to how to leave the trunk ajar without battery drain or how to route the cable around the moulding for the trunk (coupe) as to not damage the moulding leaving it overnight.

Not sure if it is a daily you should need the CTEK all the time. Only when leaving for a few days.
But since it is a tender, if the battery is fine it’ll just do nothing.

 

Good evening (For me) @Circumnavigator

I've seen life on cars videos a couple of years ago when planning on saving for my XKR. I was wondering about what mode to leave the charger in or just let it be automatic? And if constant reconnection would do more damage since the X150 is so sensitive.

If you're interested, I plan on routing the Ctek quick connector in the rear light cover within the boot to remain more subtle and easily accessible.

 

@Garron , I use this power supply. It will suffice for your needs 50 amps, low noise/ripple etc. You will need alligator clips and automotive wire to connect it to the battery. I use 12 gauge wire about 18" in length:


Here is a link to the manual you need and the wiring diagrams are also available:
JagRepair.com - Jaguar Repair Information Resource

Another manual

https://charm.li/Jaguar/2007/

Also, my two cents, this is a better tool for diagnostics. It will cover all codes, engine body , chassis and specific to your car: I use the SDD proprietary diagnostics tools but this one works for quick drill downs. I haven't used it in a while but (I think) it gives you the 6th and 7th digits on the DTC's too.

 

Have you tried a "hard reset" by disconnecting the battery for a few minutes?

 

According to the manual:

U3000-49
Control Module - Internal electronic failure

Suspect an internal fault, replace the Adaptive Front Lighting
System (AFS) Control Module as required, refer to the new
module installation note at the top of the DTC Index

 

@McJag222 Good evening,

I've just realised that what I said initially was very vauge:

When I replaced the battery, I left the car fully disconnected for around 30 minutes. I also shorted the battery leads together for about a minute before installing the new unit — the idea being to fully discharge any residual energy in the system. After that, I was still left with the airbag and AFS MILs and DTCs. My OBD tool was able to clear the airbag warning successfully (along with a few other logged faults from the low voltage event), but it wasn't able to clear the AFS fault — which is what I’m still trying to resolve.