Intermittent fault lights - fault codes read

[robbo86]

I have recently acquired a 318i and tend to get fault lights on, which ussually go out after a few miles. That's if they decide to go on at all. The three that come on are the ABS, DSC and the brake linings. Now I know the brake linings are due and that one stays on regardless, but any particular reason for the others being on to begin with, then going out after a mile or so?

Would a fault code reader show what caused the light to go on after its gone out?

Thanks in advance for your help

[hennared323i]

How old is your car?

Early E46 have the round OBD port in the engine bay and a normal OBD2 in the drivers footwell above the left foot rest. The internal one will connect to the engine only and the one under the bonnet connects to everything else.

Later (2000/2001 onwards) have one OBD2 port which is under a flap near your right knee (when sitting in the car). There is no need to unscrew anything it literally just clips down.

I have just purchased an OBD2 reader to id why my eml light keeps coming on -

http://www.ebay.co.uk/itm/291487890802? ... rmvSB=true

If it works you are welcome to borrow it as I am not far from you.

[robbo86]

It's a 2000 w plate.

[P_VIDDY]

Code read would confirm but I suspect pressure sensor. Screws in to side of master cylinder. About £90 plus at from dealer

[P_VIDDY]

Reluctor rings are common but "usually" cause the light to flicker and hold back power as it thinks the car is wheel spinning due to the incorrect signal.

[robbo86]

So I had the fault lights read today by the father in law. This is what they threw up. Sorry for crap picture but I hope you can read them. He said he'd never seen those before so I'm opening it up to you folks?

[fixedwheelnut]

Willinz and P_Viddy are right, rusty pick up wheels or magnetic swarf stuck to the bearing seal pick up if it has that type are a common cause of intermittent faults with ABS lights coming on, usually once you are up to 30mph+.

The CAN fault is a communication fault between the DME and ABS, check the power supplies and earth's to both control units and the BUS lines between them.

[robbo86]

And forgive me for the stupid question. How exactly does one check those lines?

[fixedwheelnut]

You check bus lines with an Oscilloscope to see if a message is being sent, you can check them with a volt meter and ohm meter but that can involve a lot more work disconnecting all the control units on the circuit.

Velleman do a pocket scope for about £120 worth every penny if you do a lot of electrical diagnosis

Have you checked the sensor wheels to see if they are rusty yet or damaged?

[hennared323i]

You check bus lines with an Oscilloscope to see if a message is being sent, you can check them with a volt meter and ohm meter but that can involve a lot more work disconnecting all the control units on the circuit.

Velleman do a pocket scope for about £120 worth every penny if you do a lot of electrical diagnosis

Have you checked the sensor wheels to see if they are rusty yet or damaged?

Brilliant, just brilliant answer

Time to get that degree in electronics Robbo

[fixedwheelnut]

You check bus lines with an Oscilloscope to see if a message is being sent, you can check them with a volt meter and ohm meter but that can involve a lot more work disconnecting all the control units on the circuit.

Velleman do a pocket scope for about £120 worth every penny if you do a lot of electrical diagnosis

Have you checked the sensor wheels to see if they are rusty yet or damaged?

Brilliant, just brilliant answer

Time to get that degree in electronics Robbo

Ha, ha sorry some things you can't diagnose over the internet you need to get stuck in there and have a look, I only have two balls and neither are Crystal

Now have you had a look at those sensor wheels yet to see if they are rusty or damaged, that is the first step and a piece of piss to do

[robbo86]

Sorry mate. You lost me. The hell is a sensor wheel?

[fixedwheelnut]

OK E46 318i look at this page on Real OEM part 21 is the ABS sensor at the rear, if you look where that part fits in the hub,

http://www.realoem.com/bmw/enUS/showpar ... Id=33_0840


that is where on the drive shaft you should see a toothed wheel, something like this;


If it looks rusty and damaged like the right hand one it could be the problem, quite often as the rust they expand and hit the sensor so you see shiny high spots this damages the sensor as well.


The front sensor wheel is on the inner side of the wheelbearing.
http://www.realoem.com/bmw/enUS/showpar ... Id=31_0999


Poor condition one here

[fixedwheelnut]

Got any where checking the sensor wheels yet?

[robbo86]

Not as such no... been a bit of a busy bee lately