Fault code help needed!

[television]

Got voltages from back two wheels near enough identicle, only rear right hand wheel sets the lights on. Code fault being right rear. When running the car with left rear wheel up off ground when you blip accel traction control kicks in properly. There is a brake pad wear indicator cable but not connected to pads, my last merc was like this n caused no probs but just checking, getting desperate!!
Stating 'reduced pressure' in code wouldn't mean I needed to bleed the pump or something? Calliper fault?

Callipers cannot put the warning on and the pump is not active till the pedal is pushed

 

[Mickey76]

I'm stumped!

 

[television]

I cannot explain it any better if the ABS lamp is not on when you start the car, then this shows that the electrical circuits are complete, no broken wires, and no sensors open circuit.

There is a comparator Xtal clock in the ABS pump, this is so that the pump can read the information from the wheel sensors over a wide range.
So we have a comparator with 3 or 4 inputs depending on the car, while the car is not moving all inputs here are at the same level, you start to move the car and so the rpm of all the wheels goes into this comparator, when 1 of the inputs is missing it turns the system off putting the ABS lamp on to warn you of a fault. It will turn off if tyres are different sizes back/Front, but not at low miles per hour.

A sensor may not be able to read or count.

is the car early 1998 or late for I can check to see if a blink code reader will tell you whats wrong

 

[television]

I have sent a PM to wireman to join the thread if he will, he will have his ideas for checking out your fault, and maybe that will go down better

 

[Mickey76]

Thanks
Is this a merc thing or just how normal ABS works?!
Car registered 1/5/98 but with engine components as far back as mid 97 (dates stamped on)
The rear left tyre was a different size when car had codes read, I have rectified this since(MOT failure) lower profile, now all tyres are same size, because the lights come on when car moves now this shouldn't be causing the problem???
Will check n clean front sensors. Could comparator be faulty?
Thanks again
Dave

 

[television]

Thanks
Is this a merc thing or just how normal ABS works?!
Car registered 1/5/98 but with engine components as far back as mid 97 (dates stamped on)
The rear left tyre was a different size when car had codes read, I have rectified this since(MOT failure) lower profile, now all tyres are same size, because the lights come on when car moves now this shouldn't be causing the problem???
Will check n clean front sensors. Could comparator be faulty?
Thanks again
Dave

Never known one to be faulty on a MB,,,,, you had a healthy reading from the rear, and you need the same from the front.

 

[television]

Thanks
Is this a merc thing or just how normal ABS works?!
Car registered 1/5/98 but with engine components as far back as mid 97 (dates stamped on)
The rear left tyre was a different size when car had codes read, I have rectified this since(MOT failure) lower profile, now all tyres are same size, because the lights come on when car moves now this shouldn't be causing the problem???
Will check n clean front sensors. Could comparator be faulty?
Thanks again
Dave

Never known one to be faulty on a MB,,,,, you had a healthy reading from the rear, and you need the same from the front.

 

[television]

On page 59 you have the full list of fault codes, but the blink code reader will not work on your car

http://www.mbslk.de/files/artikel/r170_fehlercodes.pdf

 

[Mickey76]

ASR sort /open circuit.... Googled this....
Mine doesn't have the sensotronic brake control
Mercedes-Bulgaria site had a lot of info, pointing at wiring between A7/3 hydraulic unit and n47 control module (ASR SPS) gives instructions on how to test. Some where on another forum via google a merc ml was cured of similar prob with some rewiring
I've been looking for an ABS code not ASR, thanks for that link will keep reading and googling

 

[Mickey76]

What do you make of site contents??? Worth perusing?

 

[Mickey76]

http://mercedes-bulgaria.com/Downlo...of 09-95, Model 170, Model 208, Model 210.pdf

 

[television]

These are the same as in the link that I gave you

 

[Mickey76]

yes but i was meaning about the fault/remedy being wiring or pump.
done their test getting --- on multimeter between pin 23 and 30, ground to rr solenoid. cant be ground as other faults would arise. pin 30 ecu to pin 8 on pump (rr solenoid) getting reading in ohms of .1/ .2 resistance, am i right that wiring is ok, leaving pump left by elimination.... according to this website of course?

 

[Mickey76]

Replaced the full section of that wire, pump to ecu.... No different, worth a shot just in case.... But while engine was running I disconnected this wire, no wheel movement from startup and it instantly set off the stream of lights.
Television you are spot on that it can't be wiring or actual sensor failure as this sets lights from startup, but also can't be a communication problem at wheels as I wouldn't be able to set lights off at standstill???

Right, so can I wire this on to maybe left rear solenoid valve on pump to check pump or would the crafty little ECU know??!!

 

[television]

Well I think it is still a poor or corrupted signal from a wheel sensor from the original description, turn key all dash lamp warnings on, start up and they all go out. move the car and the ABS lamp comes on has to be a poor or no signal from a wheel sensor. It is a pressure switch that controls the ABS lamp, any fault disables it and the lamp comes on. It has to be that way for safety reasons. it could be possible that the clock in the pump is faulty, but very rare it it was

 

[Mickey76]

Re wired bypass pump wire rr solenoid and wired it into left rear..... Guess....car behaved just the same!! Going out now to test front wheels again, jack up and spin ohm test msensors.
What should I do to eliminate things right down??
Fault code doesn't match symptoms......
Thanks again television, you will be right, just down to pinning route cause

 

[Mickey76]

A friends dad who is a mechanic said to test the system bridge the connections of the plug that the sensor plugs into on each wheel in turn and drive it after each. Did on right rear and no change, turned car off now each time I start it the lights are on immediately, what have I done? Is fuse definitely no.11?

 

[television]

I have never heard of doing such a thing,that could prove nothing, if the sensor is not open circuit possible damaged the ABS pump unit

 

[Mickey76]

Maybe should have thought first!
And that's from a mechanic!!!!

 

[television]

There was nothing wrong with the standing circuit, just one not reading correctly or it may have been the pump.

You do need someone better with STAR or things will become worse