Trying to find out why the brakes are sometimes fine and sometimes dragging (all 4 wheels) I thought I would be clever and measure the output of the brake pressure sensor with a voltmeter. Searching this forum I see an old post saying it is on the ABS hydraulic unit. The wiring diagram says I need to look for a 3 pin connector with black, green/black, and white/green wires. I found the connector but I don't find a sensor attached, instead the connector sits in a little plastic cup with the right features to hold the connector, but it just has a snap fit to the sheet metal ABS bracket. No wires, no sensor. The picture below is "plugged in" and unplugged. There is nothing that looks like a brake pressure sensor I can see anywhere else.

I see the sensor listed as Jag part C2S16180 and searching a couple of online parts places including a Jag dealer they confirm it fits my 2005 model year. Did this part get discontinued before 2005?

Any other way I can measure the brake system pressure? I hate to start buying replacement parts without understanding why the brakes aren't releasing.

 

https://www.parts.com/index.cfm?fuse...RESSURE-SWITCH

 

I can find plenty of them for sale I just can't figure out why the car doesn't have one. That little plastic piece the connector fits into is clearly engineered with all the features to hold the connector. Why would they design, build, and install a plastic part that does nothing but hold a connector that isn't used?

 

dh53: Just curious..... what is the Bosch part number stamped in the top of the hydraulic ABS module? The format will be similar to 0 265 225 XXX, where XXX are 3 digits.

From the pictures, it appears your ABS hydraulic module does not have a pressure transducer, which surprises me. The standard ABS wiring harness in our X-Types has a connector for the pressure transducer, so it looks like the dummy connector on your X-Type is safe place for the unused connector in your ABS harness. Just a guess.

Attached are pictures of the pressure transducer on my ABS hydraulic module, a Bosch part number 0 265 225 067.

 

Bosch p/n 0 265 222 021. There is another p/n 5X43-2M110-BA which I guess is the Audi p/n. No sensor and after carefully looking it over with a flashlight and a mirror I don't think there is a port to put a pressure sensor in. Looking at the electrical shop manual more closely I have a completely unsubstantiated theory that the pressure sensor is only used on cars with Dynamic Stability Control because the sensor does not show up in the ABS section, only the DSC section. I don't know what DSC is and have no idea how to check whether my car has it.

 

Dynamic Stability Control. My 2006 does not have and I looked this morning for the sensor. If you have it on your car, right next to the red PATS light is a button to engage/disengage it. Without you have coin slots.