Strange BMW fault

[James01 21]

Hi guys,

after some help have a fault with a 2010 320i which randomly comes up with a fault on the I drive for “high brake load” and “red engine malfunction warning”.

i have had it plugged in and all that comes up is a NOX sensor fault. Could a NOX sensor cause this? I have read a couple of post online about brake vacuum pump but there are no fault codes relating to the brake warning message at all.

Any help is appreciated before I start throwing parts at it. 

[Nick M.K. 574]

This sounds more like a DSC / ABS control unit fault, especially if you don't have fault codes stored in it. It's an expensive unit but various companies repair it, BMW also sell a repair kit for it.

The NOx sensor fault in the engine ECU is a coincidence, I always get them on that engine. 

[James01 21]

Hi Nick, thanks yes I didn’t think it was NOX related, as you say it always seems to pop up with that code no matter what the issue. 

Would you not think if it were an abs / dsc unit fault it would come up with a traction fault also? Also strange it sets off an EML fault also. 

Edited January 7, 2019 by James01

[Stalker 180]

There is a brake pressure sensor on the brake servo.... they are quite common for failing and causing the start stop to not work.

[Dave2302 387]

What are you using to read it ?

Chances are there are other Codes in the Engine ECU, like a CAN Comm fault transmitted from ABS DSC ECU, but you can't see it 

Agree with Nick, there are known faults and fixes with that ECU

[James01 21]

I’m not sure I got the workshop we use to read the codes, I believe they have some form of snap on. 

they said there was nothing related to abs but just a code for NOX sensor. 

Just strange to have a brake and EML light come on together. 

Edited January 7, 2019 by James01

[Stalker 180]

Whats the last 7 of the vin and ill see if it has a pressure sensor on the brake servo?

 

Ignore the NOX sensor codes for now.

[James01 21]

Hi stalker I have just cleared the codes and test drove the car again.

The fault did not reappear and the start stop is working so maybe not the sensor as you say.

It has happened twice now at random times both on road test with punters! I can’t get it to come back on when I drive it so I’m stumped. 

[Stalker 180]

You really need to be reading the dsc unit on a reliable diagnostic tool. There will defo be a code in it, if its the internal pressure sensor its a post away and repair job. (Or BMW sell a modified block unit - not sure how much they are nowadays).

[Dave2302 387]

Simply clearing codes does not fix the Problem, it may make it go away if an intermittent fault but you just know it will surface again when you least need it too.

I agree with Stalker, firstly it needs reading on BMW INPA / ISTA and second, let him run the Vin for you to see if it is that internal pressure sensor, 'cos more often than not it is  

Oh, other ECU's putting up a light at the same time as a fault in another system is commonplace these days, each ECU talks to each other "CAN Com" so you get codes appear everywhere.

[James01 21]

Thanks for your help I’ll speak to the workshop again and see if they have the required diagnostic to speak to the abs unit. 

[Stalker 180]

39 minutes ago, Dave2302 said:

Oh, other ECU's putting up a light at the same time as a fault in another system is commonplace these days, each ECU talks to each other "CAN Com" so you get codes appear everywhere.

We had a 2014 Mercedes ML250 CDI come back before christmas, with every light on the dash... every light! Airbag, EML ABS Runflat the whole lot.... for one broken wire to the NSR abs sensor!

[Dave2302 387]

Yep, I do a lot of them, also there is no longer a "Metal Trigger", it is now a magnetic Strip bonded to a metal piece that is pressed onto the CV Joints, of course when the water and salt gets to it it corrodes and falls apart 

[Raj M 0]

Hi, If it is NOx then it is emission related, so the EMS would put on DTC code at every drive cycle regardless of how many times you clear the fault code.

Power train related fault codes are expressed in P code format (Engine related). Faults associated with the ABS are expressed in C code (chassis related) I.e P0xxx for EMS and C0xxx for chassis

The issue you are facing, could be down to low voltage (faulty wiring), damaged NOx sensor, or dirty sensor pickup.

Please remember: If you see a MIL (Malfunction indicator Lamp) that stays lit up permanently on dash then its obvious the fault is emission related.

In most of the cases, it’s a simple fix since most of the people doesn’t understand the rationale about fault codes then eventually end up swapping parts when they don’t need to.

 

Edited January 8, 2019 by Raj M

[have a word with the wife 299]

a is for apple 

[Stalker 180]

5 hours ago, Raj M said:

Please remember: If you see a MIL (Malfunction indicator Lamp) that stays lit up permanently on dash then its obvious the fault is emission related.

Not always, my post above has just mentioned a Mercedes with no emissions fault but an EML light on with a manufacturers specific DTC in the engine Ecu for a lost signal from the ABS/ESP module. 

Several VAG cars put an engine management light on for ABS faults too. 

[CCC 31]

On 1/7/2019 at 1:16 PM, Dave2302 said:

Yep, I do a lot of them, also there is no longer a "Metal Trigger", it is now a magnetic Strip bonded to a metal piece that is pressed onto the CV Joints, of course when the water and salt gets to it it corrodes and falls apart 

Had an ABS light consistently trigger on an R53 MINI at about 100 yds of driving off after starting up. Always cleared within a few seconds and never occurred again in a journey. Code reader flagged as misfire on Cylinder 1 and another engine specific code. Google seemed to suggest it was likely to be a sticking bypass valve so we took a risk and changed that. Problem was still there so our local garage connected up to a more specific bit of kit which detected a difference in wheel speed on one of the fronts from the rest. Swapped over the CV joints and the problem swapped sides so problem not engine related at all despite codes, but a faulty metal strip.

Everyday seems to be a school day at the moment.

[Raj M 0]

Got you, Sorry I misunderstood the post.

 

Edited January 9, 2019 by Raj M

[Nick M.K. 574]

12 hours ago, Stalker said:

Several VAG cars put an engine management light on for ABS faults too. 

A bit ironic considering what actually triggered the VAG DIESEL emissions scandal in 2015. All they did was connect the steering angle sensor (from the ABS ECU) to the engine ECU so when there was no steering wheel input for a while (car on a test ramp for example) the engine would run leaner with fewer emissions. 

[Dave2302 387]

/\ /\ /\ LIKE

Not a lot of folks know that Nick, nice one

VW are a pain anyway regarding lights, they will often not put EML light on, but will flash Glowplug Light

I reckon it was that numpty "Pierre" who programmed Volvos, VAG and Citroens ............