R129 ? x 2

[davidsl500]

The ASR issue could be a faulty - or just dirty wheel speed sensor. The ASR works by detecting the speed of each wheel - looking for one slipping so that it can correct a potential skid.

There's a pic on this thread. Just one bolt to remove it. They get covered in iron filings which affects the sensor. Worth a look I think. If the ASR had come on at idle then it could be an ASR precharging pump issue from what I have read. I take it the ABS light does not come on as well?

On the fuel pump relay, it may be that the N16 MAS on your car has the fuel pump relay integrated within. Many issues with relays and controllers on these older cars are simply dry joints. If you know anyone into electronics you could get them to give it the once over. Also Ebay.de can be a good source for second hand units as the cars were more plentiful over there of course..

 

[rayhennig]

I feel sure that a 1990 car will not have limp mode, my 1991 300-24 doesn't and it's similar technology.

The MAS box contains the fuel pump relay and, generally, they're pretty reliable. But, as said, if you can find another at a good price, it's worth changing. Just try searching for the same part number on eBay.de, .fr, .co.uk, everywhere, in fact!

Have you cleared the error codes and tried again?

Regarding the ASR issue, I understood that the light comes on when you rev up but when stationary. Would that not eliminate speed sensors?

Good hunting.

RayH

 

[roblloyd]

Thanks for the relays.
Car will start ok as long as you do not put your foot down, no lights on the dash at this point. Only if you rev the car the ASR light comes on and the pedal is heavy.No ABS light just the ASR.
Karl from ebay r129 shop said there could be something at the back wheels telling the ASR to come on. Did not know what he was going on about until i just read Davids post.
Are the wheel speed sensors on both front and back wheels? David add a thread of a wheel speed sensor but it was on another make but it give me a idea what it looks like. Just looked again and David said there on each wheel.
Do not want to change the MAS untili know its that. The prices seem to go from $80 to £100's of pounds. Its all about what part number it is. 89 to 92 r129 prices for parts have gone up.
The car does NOT have limp mode, 1993 is when that came out on the r129, so i was told.
Cleared all the error codes time and time again.
Just had a look at the speed sensors online and i will take each 1 off over the weekend and clean them.
Thanks
Rob

 

[LostKiwi]

Mines a 1993 car and it doesn't have limp mode as such. What it does is change the feel of the accelerator pedal so the first 1/2 of the travel does nothing, then the pedal gets stiff and all the action happens in the last half. Makes it very difficult to drive but does still give full power!

 

[roblloyd]

Thats what happening to mine, just as you say lostkiwi.
Blink code reader?
Dude on benzworld told me to use the blink code with the engine running BUT the info with the code reader says to turn the key to position 2 so all the engine lights on the dash come up BUT do not run the engine. He said you must run the engine so you don't get error codes.
Can you use it with the engine running?
Thanks
Rob

 

[roblloyd]

Potentiometor , Anyone know what this is on the r129? Someone on benz world said there ASR went years ago and he said it was that word above that had gone.
Rob

 

[Richard Moakes]

1991 cars do have ASR limp mode, but it’s very analogue in operation.

The throttle is actuated by the cruise control motor in response to the position of the throttle potentiometer which is connected to the throttle cable. This is all linked together using rods and spring loaded bars and linkages.

If the ASR detects a fault, all you have is limp home mode, which is where the throttle cable is opening and closing the throttle flap mechanically without assistance from the cruise control actuator.

I have some diagnostic info, will dig it out.


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[LostKiwi]

Potentiometor , Anyone know what this is on the r129? Someone on benz world said there ASR went years ago and he said it was that word above that had gone.
Rob

A potentiometer is a variable resistor like the old rotary volume controls on transistor radios. As they change resistance by rotating a shaft they can be used as a position sensor to tell the ECU how far open (for example) the throttle is. You also find them in dashboard dimmers amongst other things.

 

[Richard Moakes]

The arrow points to the actuator

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[LostKiwi]

The arrow points to the actuator

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Man that's a hard to see arrow!

For anyone else it's blue and top right corner

 

[Richard Moakes]

The following series of videos explains it very nicely

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[Richard Moakes]

Man that's a hard to see arrow!

For anyone else it's blue and top right corner

Rear arrow is potentiometer and front arrow is actuator


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[Richard Moakes]

ASR 1 diagnostic info here https://1drv.ms/b/s!AhgVSHGRT5CRriNJ4yMr4SDhH-Ns

No blink codes


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[roblloyd]

Thanks Richard.
14 / 2 Blinks = fuel pump relay (circuit 87) not working.
14 /3 blinks = Tn/Td signal(rpm)interrupted.
14 / 4 blinks =out for oxygen sensor heater control defective.
14 / 6 blinks = output for kinkdown switch control defective.
These are the blink codes i got richard.
Will read your link you put up.
Thanks
Rob

 

[Richard Moakes]

Unfortunately the ASR on our cars doesn’t have blink codes. Those codes are for other modules.


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[roblloyd]

See i'm learning all the time.
Is it ok to use blink code with engine running? Just do not want any more cock-ups.
Rob

 

[Richard Moakes]

No problem with engine running or ignition on.

I would be cautious about clearing codes with engine running, but that’s all.


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[Richard Moakes]

Thanks Richard.
14 / 2 Blinks = fuel pump relay (circuit 87) not working.
14 /3 blinks = Tn/Td signal(rpm)interrupted.
14 / 4 blinks =out for oxygen sensor heater control defective.
14 / 6 blinks = output for kinkdown switch control defective.
These are the blink codes i got richard.
Will read your link you put up.
Thanks
Rob

Pin 14 is for ECSM, which on 129.066 is the MAS relay



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[roblloyd]

Not been able to work on the car some family problems have got in the way.But i spoke to some one who put my front brake pads on about a year ago and he said that there was a wire (its the ASR ) that had a split in it about a inch. He could see other wires inside and he just put black tape on it. He didn't get paid for doing this and forgot to tell me. So hopefully thats got worse and causing the problem. If not i will change the Mas module.
Looking at the ASR on forums there could be 10 other reasons why this has come on.
Hopefully get on it in the morning.
Rob

 

[roblloyd]

Can anyone tell me how i can test the Mas Module?
The wheel sensors do not seem to be the problem.
If anyone ever wants to get the mas module off you need to turn the knob on the top all the way around to 0 and the module just pops out. Found that out with a bit of luck.
The module looks ok and just need to test it.There are 22 pins numbered 1 to 22.
Thanks
Rob