First posting here after reading the forum now for several years (new member intro shows the car in question, 1998 XK8). Great forum with a lot of good information and expertise - I hope I could get some ideas or help for the following problem. Search did not find an exactly similar problem - or actually answers to these questions.

1998 XK8, second owner (since 2013), now about 135 000 km (about 85 000 miles), in very good condition. The Real Gauge (XK8 / XKR / XJ RealGauge - TheJagWrangler) installed.

During last winter I happened to find an unused, still in factory package 'revised' throttle body with a very reasonable price. The car was spending its winter in my garage and as a proactive measure I replaced the original TB with this unused one. After removing the original TB, the new one was installed only two-three weeks later (waiting for the gasket that was in back order) and during this time I had the battery reconnected.

After the new TB was installed, I noticed that the odometer / info display in the main instrument cluster was blank. The bulb behind the LCD was/is OK, but the LCD does not show anything, so the odometer reading and other information is not displayed.

OK, first thought was that the LCD is dead and after locating an instrument cluster which has kilometers only, I replaced the whole fascia that has the gauges and the LCD screen (as advised here in another thread). Surprise, the LCD screen is still blank. So, either in this replacement the LCD screen is also non-functional (I would think that the probability would be low), or there is something else going on.

So, either there is something wrong in the main circuit board of the instrument pack, or the new TB somehow interferes with the instrument cluster and disables the odometer. What could be going on? Any ideas?

There are a lot of used instrument clusters for sale in eBay etc which have the speedometer displayed in miles (with kilometers in small green numbers), but I would like to have the speedometer readings in kilometers only and those are hard to find with low kilometers. Before I buy the only one I have been able to locate and pay the hefty price it has, can experts confirm the following that I have understood correctly.

- My instrument cluster is LNC4300BG/101; s/w version 3.15 - have I understood correctly that I would need one identical so that it would be a direct replacement? Or would LNC4300BJ with s/w version 3.15 also work? And it does not make a difference if the cluster is from an XK8 or an XJ, as far as the software version is the same, right?
- Is it that in the American version (LNC4300AG, s/w version 3.15) the odometer reading in the cluster circuit board is recorded and displayed only in miles and changing the ml-km in the display does not affect the odometer reading? Meaning that the circuit board from an American car (easier to find) can't be used if I want to keep the odometer also in kilometers?

- most importantly, could the new TB cause this so that reverting back to the original one would bring the odometer reading back, or is it more likely that something has happened in the instrument cluster during the changing of TB?

Any other advise is also appreciated.

 

Ok this is a good one. Let me please verify a bunch of things to help you get this brain storming started:

1) Verify - the message center / display that normally shows odometer is blank under all conditions.

2) The back lights and the dimmer both work properly.

3) You replaced dashboard speedo display unit to try to fix. Same issue, nothing changed. (assumption/conclusion is that display unit #1 probably works OK)

4) This display serves multiple functions. When you press the selector at the end of the turn signal it has no effect at all.

5) Have you tried a hard reset? (disconnect + and touch to battery - terminal with its cable connected for 30 seconds) KNOW YOUR Radio code before you do!

6) This display serves as warning center: Do either the Red or Amber lights work OK? (open driver door while idling = Red light and Driver Door Open message should display, if Red works, I'm sure amber does too)

7) turn signal works OK / all headlight selections work OK (they all share wires on the turn signal's circuit board with selector switch)

8) Dimmer switch is turned all the way = Bright

9) You did not touch anything behind the dashboard to install the TPM.

10) You are certain that your battery is 100% charged.

11) None of the selection buttons on the dash (Reset; mi/km; clear) do anything that you can see.

12) Everything else works OK on the car right now.

Maybe someone who has it can post a picture of the display's electrical diagram?

Seems to me that if it is only a bad LCD display connection, the amber and red lights should work. I'm sure you answered a few of this and know the answer to many others already, but this will help us narrow it down for you I hope.

John

 

My answers are above after John's questions (in bold). The car works well, no other issues and no fault codes with a generic ELM code reader.

Jaakko

 

Very shortly, answer to all John's questions is yes, except for that with amber light can't say since there have not been any issues which would illuminate the amber light. Red warning light works, but no messages for the reason visible. Otherwise the car works as before, just the odometer reading and messages are not visible. Hard reset haven't yet tried, will have to wait until Thu when I am the next time physically close to the car.

I tried to answer a bit longer last night, but apparently screwed up something since my reply is not visible. Sorry for double posting if that reply all of a sudden should appear...

Thanks, Jaakko

 

The IP (Instrument Pack) is programmed - it is NOT Plug&Play. Even a direct replacement with the matching numbers will need programming to your vehicle. I've been down this route with a 2005 XK8 and compatible IP borrowed from my local specialist Jaguar breaker.

Graham

 

Is this also for the early models? I have an early 1998 and understood from this (https://www.jaguarforums.com/forum/x...problem-76409/) and some other threads that if you match the year, parts number and s/w version, it should be a direct replacement.

Jaakko

 

Graham, Jaako,

sounds like it's time to put the original one back in? I'm concluding that the new one must be programmed from Grahams experience.

But we will be back to a non working display in a unit that shouldn't need programming. Looks like I just walked into a loop here. Graham did I miss something?

John

 

My apologies for taking this late to report the status and what has been learned. The take-home message is that in early XK8s you can change either the display only, or the whole instrument pack with a similar one without any reprogramming needed.I have now the whole instrument pack changed, the donor was a Japanese version from the same year and it was just plug and play. Since Graham had to have reprogramming with a 2005 XK8, there seems to be a difference between the early and late models.What was wrong with my original instrument pack is not known. Dealer-level diagnostic system did not show any errors, but something was wrong with the original circuit board which resulted in no mileage reading, nor any messages visible on the LCD display, but no other problems. Most likely the original display also would have worked - though I did not test that. As the result, I have now a XK8 with only 39 000 kilometers on the odometer instead of 139 000 :-).

Cheers, jaakko