Hi. I picked up a nice 99 XK8. It has some issues and I have a few questions.

​​​​​​I Have a message that the anti lock brakes are not working. The speedometer doesn't work and when the top down button is pushed the windows roll down and then nothing else happens. I have replaced the brake control module with no change. Are these issues related? Any idea where to start? Any help is appreciated.

Mike

 

Mike, on the top. Do you hear the pump running in the trunk on the right side looking in? Have you checked the fluid level in the pump. That's just a start. Check under the rear seat on both sides near the speakers for any fluid pools.
Pull the carpet back on the right side of the trunk and you will see the pump on top of the CD player, now look along the floor and to the right of the gas tank and you will see the lines for the top going through a hole. If the floor has bits of black plastic tube covering laying there, then the top hydraulic lines are gone and most likely the connections to the pump, top latch and rams are leaking. Look near the center light fixture for fluid in the light. Not good, if you see any evidence or stains on the dash area, then don't put fluid in the pump, if it's working, because it will make a mess all over your interior.
That might get you one problem started in the right direction.
Check out the search part of the Forum for information on replacement of the brake switch, or how to fix it.
Lots of problems can appear when the battery has low voltage. That's is a understatement for sure.

 

The anti-lock message plus the speedo not working are usually an indication that a rear wheel speed sensor is faulty and needs changing. They are cheap on eBay and usually easy to swap out. It will probably be the rear right-hand side but, if in doubt, replace both.

Richard

 

Thank you. I cleaned them and I purchased new ones but I haven't installed them yet. I'll do that tomorrow. Does the top need feedback from the speedo to operate?

 

Note in any way, unless you are up to speed and try to raise it.

 

But if it doesn't know my speed because of the speedometer not working then im guessing it could lock it out but I am surprised it rolls the windows down.

 

Today I replaced both rear speed sensors and there is no change. The ABS light, check engine light are on. It says stable track error on the dic. Speedometer does not work. I replaced the brake module. No change. Where should I look next. Are there any fuses involved? I have no fuse diagram. My code reader won't read the abs codes. Maybe I invest in that .

 

You're going to need a good scanner. ABS errors do not set the Check Engine light, so you have something else going on, too.

When you said you replaced the brake module, do you mean the ABS module, left front of engine bay? If so, replaced it with what? I think these need to be coded to the car (others can chime in here if I'm wrong). Repair of the existing module is preferable unless it was somehow damaged.

 

Hi thanks for the reply, yes the abs module. I purchased a rebuilt module. I haven't read anything that said it was specific to the car. It was the same part number. My code reader doesn't do well with this car. It gives me several unknown codes. I may need to take it to a high end shop for a scan. It's a super nice car. Well taken care of. 94000 miles. But I see they are very hard to sell so I'd like to keep the cost down.

 

Thank you for the information. There is no fluid visibly leaking. The pump does not run. Only the rear windows go down and then nothing else happens. What may be the issue with the brake switch?

 

I'm sorry to hear that the speed sensors were not the problem. The fuse allocations are in the Owners Handbook which you can download for free if you don't have it. The instrument panel fuses are in the dashboard fuse boxes so you could check the fuses on both sides. You could also remove the display just to check that it's not a poor connection. It could be the speedo itself I guess. Some research might reveal a way to test it.

As others have said, I suspect that an in-depth code reader will be needed to try and pin the issues down.

Richard

 

Hi Mike,

Your inoperative speedometer is almost certainly the result of an issue with a rear ABS wheel speed sensor circuit. A common problem is a broken wire in the wiring harness for the rear sensors, usually in the free-floating section of harness between the sensor and the point where the harness is secured to the vehicle. To find the break, you can use a multimeter to test the resistance through the rear sensors by measuring at the ABS control module large electrical connector. See the pinout diagram in the attached document from our member Gus, who hosts the very helpful website jagrepair.com.

Once you know which sensor harness is open (infinite resistance), you will need either a helper to watch the meter up at the ABS control module, or a test lead long enough to connect your meter between the rear sensor connector and the ABS module. I position my meter at the rear of the vehicle near the sensor, so I can watch it as I flex the wiring harness at about every inch point between the sensor connector and the point where the harness is secured to the body. You will usually be able to find a point where flexture causes the meter to momentarily read conductivity (you'll see a blip in resistance but not 0 ohms).

Another setup that works is to bend a paperclip into a U shape and use it to jump the two contacts in the ABS module connector for the sensor circuit you are testing. Then connect your meter probes to the wheel speed sensor connector while you flex the harness to find the break.

Once you find the break, you can strip the insulation from the harness and repair the break by soldering in a short section of new wire. I use Liquid Tape and electrician's tape to reinsulate the repaired spot.

Regarding your inoperative convertible top, I seem to recall that top operation is disabled at speeds over 30 mph, so it is quite possible that your top issue is related to your speedometer issue which is related to your ABS issue....

Cheers,

Don

 

That's a very good point that it could be the wiring rather than the wheel speed sensor itself. It's not an issue that I've ever been faced with but it's well worth checking.

Richard