How (un) likely is this ??

FWIW, the Disco3 & 4 are CANbus vehicles. But then, I suppose just about everything is these days.

(BTW, horrid term, given what the "N" in "CAN" stands for.)

Yes Tim, I agree, but GOOD BMW dealers are very hard to come by. I have had my cars go through seven BMW dealership workshops, and in every single one of them, the mechanics have shown that they do not take good care of customers' cars.

But this time, I am having to do it.

My Indie, that I normally use, was not exactly certain last time I went for a diagnosis, but the wheel sensor was his best guess, and turned out to be correct. Since then, I have had work done at his establishment (by one of the youngsters) that I am very un-impressed with.

Thanks

David

I'd not expect a DVM to power up a hall effect sensor.

[...]

Where in the country are you? Someone might have a recommendation.

Chris

I keep on saying that but getting ignored. ;-)

Hi Chris,

I'm on the Sussex coast, I know of a few Indies, most I have spoken with or visited I wouldn't bother with again.

But thanks

David

OK, so how about a battery plus resistor and a moving coil meter ? I could have done that. Still could I suppose.

But anyhow, the car is booked in for a scan (or is that: I am booked in for a SCAM ??).

I am wondering what the 'repair kit' contents are, and what could fail.

When the car is turned on, the warning bong happens about three seconds of the ignition being turned on, well before any movement of the wheels. I would consider this an electrical failure being ascertained during power-on-self-test of the module and circuits.

I am one whom lets the car self test before turning the engine over, rather than key in and turn all the way to engine start. This gives time for various measurements like ambient temp, barometric pressure, air temp, coolant temp etc to be calculated by the ECUs before starting.

David

En el artículo , Huge escribió:

Why do you say that? It's a bus-based CSMA/CD serial network, not dissimilar in concept to thin-wire Ethernet, except it uses twisted pair differential signalling rather than a coax cable.

You were not ignored, you were thanked for your input.

David

[...]

Ah, OK. I just happened to know of one in Berkshire that my son has used.

Chris

Car without abs and without wheel sensors also have no problems with the speedo - the senor will be from the gearbox.

If testing in situ (and powered) you would have to turn the wheel to get both operational states.

If it's an active component and running from less than a nominal 12V then over voltage could kill more than one device at a time (or within a short period)

Most hall effect sensors are quite tolerant of voltage and work from say

5-25 volts or so. But may need a pull up or down resistor on the output.

Best way would be to tap into the output from the sensor while it's still plugged in. You should be able to see it switching with a DVM if you rotate the wheel slowly.

Unless you can find a data sheet for it which tells you what does what.

I was mixed up between VR and H/E.

But I found out that there may be nothing wrong with the sensors after all. It would be interesting to know more about how this two terminal sensor works. There seems to be one, or more PN junctions.

Again, thank you for your help and suggestions.

David

These were a 2000 Disco 2 and, although I vaguely recall it pyhsically had about 5 or 6 pins in the connector, it's a 3 wire system. From the RAVE (Rover Dealer Manual Thingy) pin 5 is power (no spec on voltage but it comes from the SLABS[1] module rather than an abitrary fuse so could be 5v), pin 1 is ground[2] and pin 4 is the signal line.

Some other info from playing with other bits of the self levelling system: The vehicle height can be controlled by the Body Control Module feeding the SLABS module a 25Hz square wave with a different mark/space ratio depending on whether it wants it to go up or down. A 50/50 cycle means "stay there", with 25%/75% splits for up and down. I used this to build in a module to drop and re-raise the suspension for trailer (un)hitching. I mention this as I'd vaguely expect to find a similar signal from the level sensors.

[1] "Self Levelling Anti Lock Brakes" [2] Or "Earth Output" as they put it. Garrrgghhhh.

After interrogating the gearbox module, there are a host of parameters available to monitor, including "mean wheel speed". So you are probably correct.

Ahh-ha, when the fuel filter was changed, the starter motor was run for a long time to deliver sufficient quantity of fuel to the HP pump from the tank. This resulted in a fault code for low voltage at terminal 30. I thought at the time that there should be a better way than using the starter motor for this priming.

Thanks

David

The BMW dealer scanned the car, their best guess was a wheel sensor failure as the fault was "an implausible signal". Not from the newer sensor, but from another wheel sensor.

But, they could not 100% sure that a new sensor would fix the problem, it may be the result of 'muck' around the ABS sensor ring interfering with the sensor, or a failure of the ring itself. This would require the replacement of the wheel bearing assembly.

So I obtained a replacement from GSF, and it turned out to be made by the same manufacturer (ATE) as the original part.

I replaced the sensor, and turned on the ignition, Bong and the lights were still on. Hmmm I rotated the wheel with the ignition on, lights still on. Hmmmm I rolled the car forwards and backwards across the drive, lights still on. Bugger.

I decided to use that car to pick up SWMBO later on. So 50 yards down the road, all the warning lights went off. Hooray.

So after three more trips, there are no fault codes present. Fingers crossed.

My next step would have been to use compressed air into the sensor hole to blow out any 'muck' before trying a replacement wheel bearing assembly.

Best wishes and thanks to all

David

there is, you either jury rig the relay or use a relay with a switch on the top that is designed for the purpose. or as I have sometimes done use a long bit of wire straight to the pump (mondeo diesel springs to mind)

(snip)

I can see that working on some cars, but on this car, the fuel pump in the tank is speed regulated by a module via signals from the CAN-BUS, from demand calculated by the engine management. The pump power supply cables come from a control unit behind the rear seat. I wouldn't want to strap the full battery supply across this set up..

My other car (petrol) primes the fuel supply when the car is unlocked, I cannot hear the diesel car doing that, but then my hearing is not that good...

Thanks

David

talk about complication for the sake of it!!