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Brake Pad Wear Light - stuck on

Vclass

New Member
Joined
Feb 28, 2006
Messages
7
Location
Reading Area
Car
Vito Sport 204
The light is on, I have had both wheels off but both sets of pads are recent and look in good condition. I tried plugging in a new sensor both front and rear and the light stays on. My OBD2 reader says "Component Brake Wear Sensor Has Short Circuit To Positive Or Line Break" so I guess I have a wiring fault. Pity the car is not telling me Front or Rear!
There is no obvious sign of damage to the wiring near the sensors. Any suggestions how I could investigate further?
 
I'm guessing that your Vito has just the basic wear sensors. They are just a loop of wire embedded in a piece of plastic. One end of wire goes to to ground, the other to a pin on the module. Inside the module that pin will be.pulled up to a power supply (probably 5, though could be vbatt) via a resistor. Assuming the sensor and wiring are intact, that pin will sit at 0v, current takes the path of least resistance. That resistance of the wire is way less than the pull up resistance . All good.
If the sensor gets worn down the wire Is broken, the pin then is no longer shorted to ground, it is pulled up to the supply voltage. As far as the module is concerned the sensor is open circuit because it has been worn down,. In reality a break anywhere would cause the same behaviour.

If the module cannot distinguish which is faulty I suspect there is only one circuit, ie the two sensors are wired in series.

Given the info above, with a multimeter you should be able to test at points along the circuit to identify if the fault is between that test point and the module or that test point and ground.
 

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