I'm guessing that when one takes off the sensors to clean them, it would be a good idea to check the resistance with a multimeter. I couldn't find my digital one when I took off the RF sensor but my 30-something year old Radio Shack meter said 6 something, I don't know enough about electrical terms to know what, but if all turned out to be the same, it would probably indicate that it was not the sensors.
Unfortunately, I'm still trying to get over installing a new timing belt on a Porsche 944 and my fingers don't feel like hoisting a wrench yet.

 

Great thread Sam. Very, very helpful.

 

Thanks for your great pictures...........We just had similar messages on my wifes XK8 AFTER changing a left rear tyre (phillips screw in tread!). Put a spare tyre on with more tread (mounted by Discount Tire!! FREE) drove the car nuts; My wife could feel the ATC system ; I drove it and car went into 'safe mode',turned it off, it reset, so drove it home and took my other spare to Discount and put on right rear. Now both rears have similar tread depths.After deleting messages and codes, recharging battery, it's fine except P1006 code.

Cheers, TTFN,Adrian 2000XK8 Conv, 2007 XK Coupe

 

Just cleaned the rear sensors; very easy. Tried firstly with wheels on, using my ramps; not enough room for my hand to separate the connector, so took off the wheels.
Senors were very cruddy................ but the toothbrush did the trick!

Thanks again for the idea........

Adrian

 

Hi Just to say I am a new member and have looked at a lot of your videos I really enjoy your style and have learned a lot.I had the wheel arch covers off today to clean behind and have alook around.I followed your instructions re jacking and axle stands all went well!
One of your videos shows the front brake calipers,mine are the same.Do you fancy making a video to show how to do a pad change I am sure a lot of members would find that useful.

 

I'd like to do that, but my brake pads are still fine. Not quite sure when I'll need to replace them. It's super simple, though, and almost all calipers are pretty much the same. Just do a search on youtube and you'll find lots of videos that give you a general idea how to change them. One thing you'll need is a really big torx bit. I'm not sure what size, but auto parts stores sell a set of 5 specifically made for removing the brake calipers. It's only $10 or so.

 

It's a 7mm hex and I bought the socket tool for 3.50 at O'reilly's.

 

Thank you both for your reply have noted the hex size.I have looked on youtube re the brakes but haven't seen any that look like ours IE with the springs.Has our caliper got a name!My front pads are also ok but just wanted to Know.

Thanks again
Alan

 

Almost all disc brake calipers have springs like that. It's to keep the pad from vibrating. It's easy to remove and reinstall, just use a screwdriver to pop it out and some pliers to put it back in.

 

Thanks Sam for your reply,reading loads of old threads enjoying all the tips.
Alan

 

Reverend Sam thanks for the great pics &video the wife has been complaining about the trac light coming on for months I didn't see it until this afternoon. She had a problem this morning where it acted like it was trying to brake but she was trying to go. Shut the car off restarted everything seemed fine after that. So cleaning the sensors will be the first thing I do. If I still have a problem I'll come back to the forum and see what I can find on the ABS repair I've seen mentioned . Thanks again for the great info

 

Thanks for the info Rev as I have this problem on my 2001 XK8. The dealer looked at it and reseated the rear sensor connector but that did not fix the problem. It is very intermittent right now. I will try cleaning the sensor as you illustrated when the weather here in CT warms up.

wcnesta

 

Did you notice it's finally getting cold around here ... as spring approaches ?!

Just curious ... did the dealer look at a rear sensor because the car threw a code indicating trouble at that spot? Reason I ask, the rear sensor wiring has to flex a little for suspension travel, but the front wiring moves a whole lot more. Wiring / connector problems up front are maybe 10x more common. You could reseat the front ones without even jacking the car ... maybe worth a try.

 

Hi Dennis

The dealer said the code indicated the driver side rear sensor. I get the error lite about three times over about 3000 miles of driving.

wcnesta

 

Hi Rev

I followed your video on how to change the lights in the dash that showed how to get the knee bolster cover off. Mine was loose at the top left corner. I removed the cover, as you showed in your video, to see why and found that the metal insert that the plastic finger slides into was missing. The other side was OK. Any idea on where I could find a replacement? I would also like to get more info on the hydraulic pressure reducer that you designed. Thanks again for all the videos you made they are a great help.

wcnesta

 

Could you be more specific, do you want the resister or the valve system?

 

Hello all,

Let me start by thanking all of the contributors to this site. It made me willing to buy an XK8 and not worry about it sending me to the poor house.

I am an electrical engineer and work with things on a daily basis that operate on the same principal so I thought I would add my 2 cents to the discussion.

A lot of discussion has been made about cleaning the sensors and intermittent wiring. I would like to add that the ABS sensors are a form of "Hall Sensor" or "proximity detector" and the exciter ring when rotating changes the capacitance and magnetic field that is sensed by the sensor.

Each time the exciter ring teeth pass by the sensor a pulse is detected by the control module. It stands to reason that if there is any ferrous material on the sensor it will not accurately or reliably count the teeth on the exciter ring and the end result will be that the sensor module (unit that counts the pulses) will falsely think that one or more wheels is traveling at a great enough variation of speed as compared to the other wheels that there is enough of a difference in traction to trip the ABS or traction control warning indicator. If that occurs the default programmed into the control module is to disable the ABS and or traction control function and revert to the good old days of wheel lock up and the impending vehicle spin that would surely follow during a panic stop.

If the sensor is dirty and that dirt contains any Iron which is used in making steel (Rotors and semi metallic brake pads)(a ferrous metal- susceptible to magnetism) it will change the efficiency of the sensor and thereby change the reading it gets from time to time. If the sensor module detects that any of the four wheels are rotating at a substantially different rate it will trigger the ABS light because the sensor module believes that one wheel or more has locked or is not getting adequate traction and the others are still moving or that a sensor has gone bad.

If sensor efficiency has changed due to it being cluttered with a ferrous material it might not count every rotation of the wheel. in essence it misses counting all of the teeth on the exciter ring and thinks that one wheel or more is rotating at a different enough speed to trip the ABS lamp.

The sensor circuit is most likely current dependent and not voltage dependent which explains why cleaning connectors and removing any dirt that inhibits a good connection solves the problem. (Current is dropped at a bad or loose connection which in effect allows less current/pulses to be sensed by the control module) Less current sensed by the control module simulates a different wheel speed by artificially altering the number of rotations counted as the exciter ring passes the sensor.

Imagine an old childs toy that used magnets and what would happen to the toy if you covered one of the magnets with iron dust. (Like lead pencil shavings) Remember the hairy look it got? Same principle here. It is changing the direction of the "E" and "H" fields of the detected pulse thereby reducing the efficiency and induction of the hall/proximity sensor and the subsequent result is lost counts/pulses detected by the control module.

Cleaning the sensor makes perfect sense to eliminate this intermittent nuisance problem and if that doesn't work cleaning all of the connection points or removing them and hard wiring them using solder and shrink wrap would be my next step. By removing all of the connection points required to efficiently assemble the vehicle when new you eliminate the potential for unwanted drop's in the current required to develop a strong enough pulse to be read by the sensor control module.

Clear as Mud right?

I hope this adds a little more understanding for some of the people on this site of how the system is designed and intended to function. I am a firm believer that if we know ho something is intended to work it makes it easier to diagnose when things don't work as they should.

BTW I will be cleaning my sensor this weekend when I do a complete brake job.

Thanks again for the great insights that the contributors offer to the readers of this forum.

Barry

 

Barryl,

Some good insights in what you posted.

Generally, when guys discuss here cleaning sensors, I think they're referring to the (non-ferrous) metallic casing of the sensors.

But as you noted electrical connectors can need cleaning too, and this sometimes gets done, even if by accident, in the process of unseating and re-seating the connectors ... which guys sometimes do to remove the sensors for cleaning. In other words, we might think cleaning a sensor body fixed a particular problem, but it might have actually been reseating the connector that did it. I bet this happens sometimes.

All in all the system is just plain cranky. But as often as not it's dirty sensor casings or intermittent connectors or broken wires at/near the sensors.

The latter two of these usually show up on a front wheel, where the sensor wiring has to flex with steering inputs and with suspension travel.

I don't know if these problems went away with the 2007+ XKs. But they sure should have.

 

Hi Gus

I want the resistor assy.

 

Hey I just cleaned my front sensors ...does that ground wire go first or on top of sensor...