BMW E46 325ci 2002 - ABS Fault

[FilipeCMartins]

Hey everyone,

I’ve had an issue with my ABS light, brake light and what I think is the traction control light all coming on yellow and the breaks sometimes shudder when I use them.

Initially my brake pad wear warning light came on, and then a week or so later these three lights started coming on. I’ve know changed my brake pads but they other three lights are still on!

I’ve checked the resistance readings on all four wheel speed sensors, and they all read around 3.3kohms. I’ve also checked fuses related to the ABS system and they are all fine.

Sometimes the lights all go off and everything seems fine, but then they all come on again randomly.

What else can I check related to this?

[RUSSELLM]

What fault codes are you getting ?

[E30M3SE]

RUSSELLM said:

What fault codes are you getting ?

This.

There are two pressure sensors screwed into the brake master cylinder, they are a possible cause of your issues but you need to do a code read first. If it is the pressure sensors they are around £130+vat each from BMW dealers and a fairly easy fit.

[FilipeCMartins]

So the only scanner that I have to plug in is an OBDII reader, and these are the faults I get with that:

P0056 HO2S Bank 2 Sensor 2 Hester Circuit

P0171 System too Lean (Bank 1)

P0174 System too Lean (Bank 2)

Not sure if any of these are relevant. Are there more codes that I need another reader to get access to?

[FilipeCMartins]

E30M3SE said:

RUSSELLM said:

What fault codes are you getting ?

This.

There are two pressure sensors screwed into the brake master cylinder, they are a possible cause of your issues but you need to do a code read first. If it is the pressure sensors they are around £130+vat each from BMW dealers and a fairly easy fit.

I’ve seen this fault online but it doesn’t usually seem to bring up the ABS light aswell?

[g3org3y]

FilipeCMartins said:

So the only scanner that I have to plug in is an OBDII reader, and these are the faults I get with that:

P0056 HO2S Bank 2 Sensor 2 Hester Circuit

P0171 System too Lean (Bank 1)

P0174 System too Lean (Bank 2)

Not sure if any of these are relevant. Are there more codes that I need another reader to get access to?

None of those are relevant to the braking system.

Is your code reader a generic one or BMW specific?

[helix402]

I think the op has scanned obd codes only with a generic tool. This won’t check the ABS/DSC system for codes.

[RUSSELLM]

I concur

[anonymous-user]

you sure its the brakes juddering and not misfiring when off throttle?
I had those 3 lights come on and after much faffing with other stuff it turned out to be a dodgy maf.

Definitely scan the abs module first though to be sure

[Maxus]

This sounds very much like a wheel speed sensor to me. They work in 2 parts - the sensor itself and the reluctor ring on the hub.
When mine failed I got the same warning lights as you and grinding brakes sensation when stopping. I have the BMW diagnostic software which allows me to get a live reading of wheel speeds when moving. Quite clear that one wheel was all over the place. It was the sensor that had failed.
I had the same failure on a MINI. Changed the sensor with no luck. Needed a hub change which fixed it.

[smn159]

I had something similar on a Volvo V70 when the driveshaft bolt under the wheel centre cap came loose and allowed the reluctor ring to move slightly.

I found it only after I'd fitted a new sensor and bashed on a new sensor ring and it still gave the same errors

[g3org3y]

Maxus said:

This sounds very much like a wheel speed sensor to me. They work in 2 parts - the sensor itself and the reluctor ring on the hub.
When mine failed I got the same warning lights as you and grinding brakes sensation when stopping. I have the BMW diagnostic software which allows me to get a live reading of wheel speeds when moving. Quite clear that one wheel was all over the place. It was the sensor that had failed.
I had the same failure on a MINI. Changed the sensor with no luck. Needed a hub change which fixed it.

My wheel speed sensor failure resulted in this on the dash:



(And wheel speed sensor issue on the code reader).