Hi All.

I'm doing my best to search first and ask later!!

My XK8 came up with the Engine Management Light in solid orange. I bought a code reader which gave me P1642 P1646, with P1111 (pending) and P1647 (pending)

Code reader is a sealey OBDII AutoLink AL301

I've read the threads about P1646 and the confusion with using the same code for different things depending upon which car you have! As far as I can determine, with a 2001 XK8 4.0 the codes P1646 and P1647 must relate to the O2 sensor heaters, but I can't believe that both have malfunctioned at the same time?

Owing to poor weather and no time, my XK8 had sat in the garage for 2 weeks so I took it out for a run, then got the engine management light when I started it up again later on.

I was planning on erasing the codes and seeing if they come straight back, but the code reader shows ERASE FAIL when asked to do so.

I'm also in the process of downloading the JTIS file from the sticky, but I've already seen that the thread posts it relates to are XK cars not a 2001 XK8? or are the codes all the same - would appear not given the P1646 threads?

Advice would be appreciated.

 

All the official reference documentation is here:

JaguarXK8ElectricalOBDIIcodes

You can check both the PDF for the codes and the PDF for the electrical diagrams. Make sure you pick the right VIN range/Model year. For these codes, they refer to the heater circuit of the O2 sensors. These circuits are protected by a fuse (check it!), and powered through relays (swap them to check).

Separately, if the car has been sitting a lot, triple check the battery. Check the voltage at rest (should be well above 12V), check the manufacturing date sticker and match it with the warranty. Anything over, say, 4 years, should be suspicious. Be careful for acid splashes, but if the battery is not maintenance free (AGM), check if you can pop the cap and top off each cell with distilled water. You might get a fraction of a Volt back. These cars are loaded with electronics that get very confused with a weak battery as the voltage drops too low when the starter is activated.

Chances are you will have to replace these sensors, but you might want to eliminate all the zero-dollar (or pound equivalent) opportunities first, and move on to spending more money only if you have to.

Best of luck, keep us posted.

 

Thanks for the links.

Given what I've read about the cars electronics, I was intending to check the battery. If I put a new one in, do you need to maintain a 12v current at all times or doesn't that matter?

If I disconnect the battery for long enough it would clear the error codes anyway?

I wanted to clear the error codes and charge the battery and see if they came back up again, but the code reader says erase fail and wont get rid of them at the moment.

As you say, start with the cheap and easy stuff and makes sure its not that!

 

If you change the battery then take about 10 minutes to do it, this will allow the volatile memories to erase and some codes. When reconnecting you will need your radio code and windows resetting, no great shakes, takes two minutes.

If you don't have one, I suggest you get a CTEK battery maintainer and hook the car up when you're not using it. It will help reduce spurious electrical gremlins.

 

When I bought my XK8 I didn't realise how much reading I was going to have to do!! LOL

Add find radio code and how to reset windows to the list of things to do.....

Cheers

 

Found the windows one now....

Awesome forum this.......

 

The windows are easy. Press and hold on the down, when the window is fully down keep hold of the switch until you hear a faint click. Press and hold on the up, when the window is fully up keep hold of the switch until you hear a faint click. Do this with the doors closed and ignition on. Simples.

If you can't find the code, drop into your local dealer with your paperwork and they will get it for you.

 

Yes, but the point is that the material is available for us to read in the first place. There are lots of other great cars out there without anywhere near the amount of documentation we have. For me, this is one major contributor to getting this car, and also how we are sometimes able to help each other out.

 

OK battery is fine, I charged it up and its holding fine at 12.75v

I'm trying to identify which fuse(s) relate to the HO2S upstream heaters (which is what P1646 is telling me is the problem)

Also, is there just one relay operating the A and B upstream heaters? The suggestion is to swap the relay (which as far as I can determine is in the EM fuse box up by the bulkhead on the passenger side - mines a RHD) but what do you swap it with? Best to get a spare relay? I assumed that there would be two relays, one for A and one for B but it seems not, so I can't just swap them around and see if the problem moves to the opposite side which would indicate that its the relay and not the heater?

Appreciate any input.

 

Steve have a look here at page 04.1. http://www.jagrepair.com/images/Auto.../jagxk2001.pdf
You will see fuse F14 10A supplies the relay and fuse F1 30A supplies the heaters. Both fuses and relay are in the engine management fuse box.

 

Hmm, this is a CAN bus error. From the book:

"CAN short circuit fault
Control module failure –
check for additional flagged DTC(s) to locate control module source"

You might have to do more research on this. Only a few modules are on the CAN bus, so one of them is possibly bad and prevents the bus from passing on any message. The other possibility is that the CAN wires are shorted somewhere. Was there any work done on the car recently?

There was a TSB for the instrument cluster, with a VIN range: 413-S484am2 INSTPK CAN failure.pdf

Is this code still there?

 

Not sure, as I cant check the codes as I left the code reader at work!!

I've checked the fuses in the engine management, they are OK

I'll bring the scanner home tomorrow and see if it will read and erase the codes now the battery has been disconnected for hours. The Engine Management light on the dash is still on though, even after the battery disconnect all day.

I'll update you tomorrow when I can check it.

Many thanks

 

fuses are ok, I need to get a new relay to check that unless there is an easy way to swap it with another one?

 

Look for one with the same rating using the diagrams, but safer to get a new one. Worth checking and exercising the connector at the ECM also.

 

According to my reading of it, the relay that is in the Engine Management Fuse Box is the EMS Control relay and not the heater relay? I think the heater relay is in the Engine Management Module box, shown in fig 04.1? I assume that the EMM box is the larger black box closer to the bulkhead which is secured by 4 safety screws (one of which refuses to budge at the moment!)

Or am I reading it wrong?

 

VIN is much later than those. Mine is A23586

I haven't had much experience of this sort of investigation, but I assume that you take the first error code first?

So the P1642 then P1646?

What baffles me is that I then had a P1111 pending, which would mean that the car was "ready" and all circuits etc correctly functioning? And then a pending P1647 which is the B side HO2S!

So I was inclined to think it was an electronic glitch, which I wanted to clear with the scanner and see what returned.

 

Hi Steve,
The relay you seek is shown here:


The lid with the safety screws hides the engine management and transmission control modules.


HTH,

Mike

 

Just as an update, as I continued to tinker with things and check various suggestions, completely out of the blue on starting the car on Sunday, the engine management light switched itself off! I'm going to recheck the codes to see if all the codes are now cleared (although a bit of me says - Don't touch it!! Its fine!!)

It runs beautifully (as its always done) so I was inclined to think it was an electronic ghost. I had the headlights switched to auto, so they actually came on with the ignition even if I didn't start the car, and I also had a session of programming a new fob or two, which also requires a sequence of holding and flashing the main beam lights on. I suppose its possible that the combination of all this allowed the battery to drop to a lower than acceptable level which might have caused it.

I'm going to get a battery charger/conditioner so that I can leave it plugged in when the car is not going to be used for a bit. Hopefully, things will be stable for a bit now.

On the upside, I'm already far more knowledgeable about the beast already!

 

The codes stay stored for a long time but can be ignored if the MIL is off (unless you want to do troubleshooting).

 

the p1646 code returned so I'm back investigating. The relay as shown in your diagram doesn't exist on my car. There is the bank of three as shown in your diagram but not the 4 th one which is the relay I'm after? The front of the car is to the left of the picture