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Discussion Starter #1 (Edited)
2003 E46 330i Saloon: So this weekend the DSC light (Orange Triangle) has been coming on and wheels juddering when I've been going slowly, about 20 mph, turning sharp right. I didn't notice the light at first as the steering wheel was turned 90 degrees and obscuring it but then I noticed it flashes and when I turn the wheels back straight ahead the juddering stops and the light goes out. It occasionally happens on acceleration / deceleration in a straight line but is harder to replicate. I can replicate it every time when turning right.

No brake light comes on, just the orange DSC Triangle .

So my first thoughts are an iffy traction control wheel sensor. I had a look at each wheel yesterday just to check for frayed cables etc but all looked OK.

I thought of measuring the resistance of each sensor but the 2 terminals are quite deep within the plug connector so hard to get a probe on.

My OBD2 Android App doesn't give any error codes and a call to the BMW dealer reveals he wants £175 + VAT to diagnose it.

Any thoughts which sensor it could be based on it only ever happens when turning Right and never when turning left ?

Oh and it won't come on until the engine has warmed up so I assume the sensors aren't monitored until the ECU goes into Open Loop.

thanks

PS A bit of googling suggests its the sensor on the opposite side to which you turn, so in my case that would be one of the left wheels. Apparently an INPA diagnostic software can display the wheel speed data only trouble is I don't have a laptop.

Can anyone recommend an Android OBD2 app that displays wheel speed data on an e46 ?
 

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2004 330Ci 85k miles
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INPA is the best software for diagnosing this. It can show DSC live data such as wheel speed sensors, and lets you see and clear DSC trouble codes. You need a K+DCAN cable (with built-in switch) and a Windows laptop.
Hit the BMW Standard Tools link in my sig for how to set it up.
 

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Lol 20 mph sharp turns isnt exactly that slow. Are you sure your not just literally losing traction? How’s your tire condition? It sounds like your describing the dsc working normally. One of your tires could be dangerously low and messing with it
 

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Discussion Starter #4
INPA is the best software for diagnosing this. It can show DSC live data such as wheel speed sensors, and lets you see and clear DSC trouble codes. You need a K+DCAN cable (with built-in switch) and a Windows laptop.
Hit the BMW Standard Tools link in my sig for how to set it up.
thankyou, I'll load up INPA and find out which wheel is playing up
 

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Discussion Starter #6 (Edited)
I want to make sure the cable I get is correct, this is the description on the eBay listing:

D-CAN for
1: E60, E61 od 03/2007
2: E83 od 09/2006
3: E81, E87 od 03/2007
4: E90, E91, E92, E93 od 03/2007
5: E70 (new model X5)
6: R56 (new model MINI)
PT-CAN, K-CAN - fully switchable speed of magisterial CAN - you can diagnose driver without any car

Protocol for BMW OBD interface for Older Cars
From 1995 to 1998 (don't need K-line).
From 1998 to 03/2013 (all models)


Although it doesn't mention E46 does it look like the right one ?
thanks

Screenshot - 16_09_2020 , 09_43_26.png
 

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I'm thinking towards steering angle sensor, but this is a wild guess. Live data/fault memory is step one.
 

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Lol 20 mph sharp turns isnt exactly that slow. Are you sure your not just literally losing traction? How’s your tire condition? It sounds like your describing the dsc working normally. One of your tires could be dangerously low and messing with it

This.

You are describing the DSC being activated. The light flashes to tell you that the system is doing its job, it's on steady to tell you that it's not going to work when you think that it should. The car thinks it is drifting (sliding) and the DSC is turning on to control the slide. The car uses the wheel speed sensors and steering angle sensor to calculate lateral loads, and when the loads exceed some parameter, the DSC applies the brakes and cuts the throttle.

If you have a low tire somewhere, the car will detect the speed difference of the tires as part of the calculation on lateral load. The same is true if you have mismatched tires, and if the tires are mismatched and one is low, then all sorts of chaos will happen.
 

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BEFORE you go off on system diagnostics, you are describing issues that might arise from tires that are low on air, and if you have staggered tires, the front and rear tires are not compatible/complementary. If you have non-staggered tires, but have a 225/45x17 on the front and a 235/50x17 on the rear (for example) then this will also give you troubles with the DSC.
 

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Discussion Starter #11 (Edited)
Hi thanks for the confirmation of the cable.

re: how the DSC works / tyres. The fault only occurs when turning right. Turning left at same speed nothing happens. The tyres are all of the correct size and pressure. There are no issues with tyre degradation that I can see, the car only passed its MOT inspection 3 weeks ago which includes a tyre check although of course that wouldn't confirm a collapsed or weak tyre wall unless it was visually obvious

I have owned the car for 15 years and drive it every day. This is the first time the problem has occurred since I've owned it and it only started happening about 10 days ago going round a roundabout - hence the right turns we have over here

My thoughts are: due to the cars age, 17 years, I'm going with a reluctor ring that has expanded slightly due to surface rust and damaged the end of a wheel sensor. The question is which one .. hence the INPA & cable as my simple OBD2 sensor and Android app can't check those sensors.

Once I have narrowed it down to a particular corner I'll know if it is a sensor or indeed a dodgy tyre. Or I could swap the rear tyres L-R and see if the problem moves to when turning left and if not do the same on the front tyres ....
 

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Discussion Starter #12 (Edited)
I'm thinking towards steering angle sensor, but this is a wild guess. Live data/fault memory is step one.
out of interest where is the steering angle sensor ?

edit: it's ok component locations explained in the excellent DSC article, thanks for the link
 

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Hi JGrant,

I put together a guide that may be of use once you have got INPA set up. Whilst specifically directed at trifecta lights, it contains some other useful information regarding ASC and DSC functions that may be of assistance with diagnosing and understanding the fault.

 

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Discussion Starter #15
Hi JGrant,

I put together a guide that may be of use once you have got INPA set up. Whilst specifically directed at trifecta lights, it contains some other useful information regarding ASC and DSC functions that may be of assistance with diagnosing and understanding the fault.

Hi, I just had a very quick read, it looks like an excellent guide. I'm sure it will be very useful to me
many thanks for the link
 
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