DSC Pressure Sensor Replacement

[DetroitMatt]

I've got the dreaded trifecta of brake warning lights: ABS, DSC, and Brake on my 2003 X5 4.4i. It still happens intermittently, but after doing all the research on here, I'm pretty sure it's the ABS module, but I took it in to get it scanned anyway. The BMW specialist / INDY said that it came up:

Bad brake light switch,
and Bad DSC Pressure sensor.

Even though I still think it's the ABS module, I decided to work backwards from cheap to expensive just to be safe. I replaced the brake light switch ($40) and nothing changed. I also bought a DSC pressure sensor for $130 and plan on replacing that tomorrow. I figure if that doesn't fix it, then I'll know 100% that it's the ABS module and I can send it in for rebuild or replace it and reprogram it.

My question is: Is replacing the DSC ABS pressure sensor as easy as just swapping out the old with the new one, then just plug it back in?

I've heard conflicting reports on other sites. Some say just swap it out. Others say you need one of the BMW diagnostic computers to put the ABS pump in bleed mode, and bleed the entire braking system afterwards. The one actual report from someone who did it on his 5-series said it wasn't under pressure and he just changed it out. His lights went out and all was well.

Has anyone replaced this before? Do I need to bleed the system? Or can I just unscrew the old one out, and screw in the new one, plug it back in and be on my way?

PS: The part number is: 34 51 1 165 467 if anyone's wondering.

Thanks in advance if anyone has any experience in this to share!

[Weasel]

If you get an air pocket in there you may need the diagnostic computer to bleed it, but I haven't needed to do that to change the sensor yet. The sensor is pretty easy to change, it is right there on the DSC hydraulic unit. Remove the old one (not much fluid comes out at all), screw the new one all the way then back it off a partial turn, then have someone lightly press the brakes for you to press the air out right at the sensor till brake fluid seeps out of threads, at this point tighten it then they can let off the brakes.

And yes, I've seen the pressure sensor cause the issues you describe. If the DSC module sees brake system pressure without seeing brake pedal sensor input it knows something is wrong. The pressure sensor was likely the only cause, the brake pedal switch just had a plausibility fault due to the other failed sensor.

[DetroitMatt]

Thanks for the info! I figured it wouldn't be too much of an issue as long as it's swapped out quickly. The air that would get in would be negligible. I'll do exactly what you said tonight and we'll see what happens. Would be nice if it was the pressure sensor. Would love to avoid the hassle of dealing with the ABS module.