Hello!

I'm a new Jag owner, finally acquiring a 2004 XJ VDP, in great shape, good miles, and with the DVD system in it that my munchkin loves. Thought I would share an issue we are currently working through.

The car came with service records for the past 5 years, which show 3 of the air shocks replaced with Arnotts, several height sensors, a wheel sensor, and many other maintenance actions. The serpentine belt was replaced along with a tensioner, engine thermostat, coolant flushed, etc.. The previous owner paid some serious repair bills over the years.

One nagging issue she complained about was the transmission shifting poorly. I've read enough of the forum to understand that there were some service bulletins for the 2004 involving flashing the TCM and ECM, changing the transmission pan and replacing fluid, and having the learning module cleared and relearning shift points. It appears the previous owner had many of those things done, but the problem persisted, albeit with the shift issue being only a minor annoyance, not a major problem. I've driven the car a few weeks and realized it probably wasn't at 100%, but it was acceptable.

So I took it to a local indie mechanic, and found something that might interest others. Turns out the sunroof drain on one corner had a kink in it. Whether that was from the factory, a poor install job, or an owner messing with it along the line will never be known. But the result was that moisture didn't drain properly, and accumulated under the rear seat. An electrical connector there eventually corroded. The mechanic I am working with noted a lot of codes stored, traced the system, and found/fixed the corrosion. I had been having issues with ABS, air suspension, DSC, ride height, etc. All seemingly random.

So the working theory is that since this corrosion didn't appear overnight, it may have been there for several years. It seems plausible that many of the car's issues could have originated from the root cause of a simple plugged rubber tube that went undetected by previous technicians, allowing the corrosion to continue.

As an example of what we are thinking, it seems to make sense that if the signal from the ride height sensors was sporadic and threw a code, then a mechanic diagnosed the need for installing Arnott air shocks. The previous owner had been complaining of the car sitting low on one side. And since the transmission likely gets some signal from the wheel sensors regarding speed and when to shift, then the same corrosion could be responsible for the shift issues.

We are proceeding step-by-step to figure out whether this single, but critical corroded connector is indeed the common thread in multiple issues over the years. If they clear up without throwing more parts at the problem, then I'll be a happy Jag owner!

Anyone else ever see an issue like that? Comments on our working theory?

 

Hi Florida_Pilot,

First of all, congratulations on finding an independent mechanic who is knowledgeable and thorough in his diagnosis procedures. Please pass along to him our appreciation for his good work.

Secondly, thank you for your informative and helpful post! Is there a chance you took a photo of the specific electrical connector that corroded and caused your problems and could post the photo here? It would certainly help the rest of us know what to look for.

Cheers,

Don

 

A photo would be a great help. It would be worthwhile just to check.
The plugged sunroof drains is a big issue with Audi A8 variants. These share many features with the same vintage XJ (aluminum body, Bilstein active air springs, transmission, and Lemforder suspension bits. One of the flaws of the A8, the roof drains, the firewall drains, and the evaporator core drains all plug up. Mine has had plugging of all three.