01 740iL - ABS/BRAKE/TRACTION CONTROL light on

2001 BMW 740iL

i have the ABS/BRAKE/TRACTION CONTROL light on

scanner said "PRESSURE SENSOR, LINE" FAULT CODE 51

changed the sensor and reset the code and nothing changed

what could it be? ABS MODULE? i dont want to start throwing money at this car as this is my 2nd car but i would want everything to work. so i need your help guys.

With all 3 lights on, it very well could be the ABS module.

But, it could also be a wheel speed sensor. I'd double check the wiring on each wheel speed sensor, as they have been known to get old & brittle & crack, causing problems.

I don't recall for sure, but it's either the 2 front or the 2 read wheel speed sensors that cause the lights to come on.

How to check wheel speed sensors/diagnose the culprit: http://www.bimmerfest.com/forums/sho...1&postcount=48


For your information read bluebee's post http://www.bimmerfest.com/forums/sho...d.php?t=527750 . That apply's to E38.

Originally Posted by Seven11

scanner said "PRESSURE SENSOR, LINE" FAULT CODE 51
changed the sensor and reset the code and nothing changed

This is, unfortunately, all too typical. In fact, when I scanned, I also had the same fault code. Yet, it was a red herring.

More details here:
- ABS BRAKE DSC trifecta brake pressure sensor diagnostic test DIY (1)

Originally Posted by joyism5

How to check wheel speed sensors/diagnose the culprit

Yup! Joyism5 is on the money. That one ABS trifecta thread has had over 200,000 visitors in just a couple of years ... so all the crazy misconceptions have been weeded out looooong ago ... and better yet ... all the good ideas from hundreds upon hundreds of users are in that one thread.

For example: It's almost NEVER the brake pressure sensor. In fact, I don't think we've seen more than one or two cases when it was the brake pressure sensor, if that. So, you're welcome to replace it ... but reading the thread is muuuch cheaper!

Yes, I admit. It's a long read - but - in the end, you'll diagnose and solve your ABS trifecta problem in less time than it took you to read the thread in the first place!

changing that sensor is useless and waste if $$. Your probblen is your ABS DSC control module. Either replace the module with new or have yours refurbished. I got mine refurbished @ www.modulemasters.com..$300 and item came back with new and improved ...it was Plug n PLAY...Highly recommended

This sure does stink, got the same error on my Mazda the other day. All three lights came on at once also.

Originally Posted by JoeC9

All three lights came on at once also.

The referenced thread has probably a couple hundred people posting what happened to them - and how they fixed it (including me).

It turns out that the trifecta is the trifecta, no matter whether it's intermittent or if the lights come on at once, or if they only come on Fridays when you've had too much garlic on your pizza.

The root cause is almost always either a single wheel speed sensor went bad or the 7th silvered wire lifted off its gold bondpad inside the ABS control module.

All four sensors are usually easy to test in about five or ten minutes without even jacking the car up ... so read the thread for how because it will take me longer to type this up than for folks to test the four sensors with the quick tests.

About 10% of the time, people have problems with the quick test - but 99% of those are user error or a bad DMM so, for the most part, this test will be conclusive in just a few minutes.

If a single sensor tests bad, you replace it. If more then one test bad, then strongly suspect your technique and DMM - because more than a few people have bought 4 new sensors for the E39 only to still have the trifecta (Bosch 5.7 ABS).

Most people whose sensors test good (I was one of them) simply send their ABS control module out for repair by the big three and that's it. The problem is solved. About 25% of those people have to buy a reman or new ABS control module (rough percentages) which never ever costs more than a few hundred dollars (the thread has all the details). Mine was fixed for about a hundred bucks (IIRC) but I took the risk of going to the low-ball rebuilders who actually have a bad reputation (years later, mine is still working - but maybe I was lucky).

We didn't have this information when my ABS control module went bad, but the thread shows exactly which wire and how to test it so you 'can' open up your ABS control module to take a look.

If the 7th silvered wire is loose, then you've found your culprit. Most still send it out at this point, which the rebuilders will take even though it was opened, as it's very difficult to reattach without good equipment and experience.

In summary, the trifecta (and the bifecta, it appears) are almost always due to a single bad wheel speed sensor or to the 7th silvered wire.

Both have simple tests which cost nothing more than a DMM, paper clip for the sensors and an exacto knife & a toothpick for the ABS control module.

Note: You 'can' get fancy with the diagnostics ... but the thread has tons of information on why that often is the road to folly - so I'll let you read it on your own.

Shoot I have this light illuminated as well! My cc doesn't work and neither does my speedo and odometer.... are the problems I've stated related to this trifecta????
So I should start at testing each of the four wheel sensors???
OMG going on overload here! Lol!
Please advise,

(Darn it! My opinion is there's never enough garlic!)

Hi, new to the forums. Just bought a used 01 E38 with 110K. This exact same issue just came up with my car also, and its very annoying. I want to ask anyone here that experienced the same issue, did they feel a decrese in power from the engine? I did and also the steering felt like I had no power steering. After shutting down the car for a minute and restarting it, all the warning lights would go off and engine seemes back to normal.

I did mees around with the right rear speed/abs sensor and the light went off untill I started driving again, hopefully thats my only problem right now. But I noticed on the left rear there was a blue & black sensor. Whats the black one for? Thanks for any help. I love the car but this makes me hate it right now.

Originally Posted by 97E38girl

are the problems I've stated related to this trifecta?

From the referenced thread, these are my DMM readings which also reveal, on the E39 anyway, which wheel sensor innervates what:
- How to diagnose the BMW ABS BRAKE DSC/ASC trifecta (1)

Originally Posted by 97E38girl

So I should start at testing each of the four wheel sensors??

If you have the trifecta, the first thing to test is each of the wheel speed sensors. On the E39, it takes about 15 minutes and the only tool you need is a DMM and a paper clip.

Originally Posted by 97E38girl

there's never enough garlic!)

I agree! Here's how I ward off the dreaded airbag light!

Originally Posted by Almar48a

on the left rear there was a blue & black sensor. Whats the black one for?

On the E39, the blue and black connectors are for the wheel speed sensors of which there are four and brake wear sensor, of which there are only two.

Here's a pic re-used from the canonical trifecta thread:


Here is a canonical set of links from the E39 bestlinks (almost all, if not all of which applies to the E38):
- How to diagnose the BMW amber ABS BRAKE DSC/ASC trifecta or bifecta (1) & what are all known options when your ABS control module is bad (1) & Quick99Si's explanation of why the 10-minute wheel speed sensor diode-action quick test doesn't always work, especially on brand new non-OEM wheel speed sensors (1) (2) & explanations by 540iman as to why the fancy diagnostic tools very often (extremely often, like almost all the time) fail to properly diagnose the trifecta or bifecta (1) (2) (3) (4) (5) (6) & where to get the fancy schmancy diagnostic tools for free once you're aware of these limitations (1) & an ABS BRAKE DSC trifecta brake pressure sensor diagnostic DIY (1)

hi i have had a diagnostic test done on my e38 728i , as my abs lights come on when i accelorate to 3omph under that no lights on,
the test results say error 92 which means precharger pump is faulty got a used 1 with warranty and its being fitted on monday ,