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MX5 NC wheel speed sensor not reading


Gavin Magee

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Having some trouble getting any signal at all from this sensor (in normal use). This car is an MX5 NC. It has a Honda K20 engine with G4X DC5 plugin. 

I have wired the front right abs sensor (2 wire sensor) directy to DI2 input (via OEM ECU header). This is an isolated sensor... as in, it is not connected to any ABS system etc... just the Link ECU only.

I can connect and disconnect the sensor itself while watching the F12 window and I can see some random frequency data showing as I do this, so I know the wiring is at least making a connection. I have tried reversing the polarity of the sensor by switching the sig/gnd wires. Yet when the sensor is connected and fitted I get zero signal from it when spinning the wheel or driving the car.

I should add that this is a brand new sensor and hub assembly from Mazda and I have even went as far as trying a replacement sensor from another known working vehicle. Still no signal.

Tried changing all input settings I could see in the software (internal pullup, trig edge and so on).

I assigned GP speed 1 with DI2 as the input. Then set driving wheel speed source to GP speed 1 (driven wheel speed source OFF)

image.thumb.png.1a9dd426367a478d07eb55d0d1a28d0c.png

 

I would be reasonably confident there is something I have overlooked. Calibration attached below. If someone could take a quick look it would be appreciated.

William MX5 K20.pclx

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Is it a standard 2 wire reluctor sensor? how fast have you tried driving with it?

The abs sensors I am used to are 2 wire reluctor and need the pullup off and a wheel speed of about 20-25kph before the ECU picks it up. There are more modern sensors which require more complicated hardware to read.

Not the most familiar with the NC but does it have a CAN bus system on which you could just read the wheel speeds being transmitted from the ABS unit?

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11 hours ago, Vaughan said:

Is it a standard 2 wire reluctor sensor? how fast have you tried driving with it?

The abs sensors I am used to are 2 wire reluctor and need the pullup off and a wheel speed of about 20-25kph before the ECU picks it up. There are more modern sensors which require more complicated hardware to read.

Not the most familiar with the NC but does it have a CAN bus system on which you could just read the wheel speeds being transmitted from the ABS unit?

It's a 2 wire sensor, which I had assumed is a normal reluctor sensor, but maybe it is a different type?

I drove the car to at least 50-60mph and still zero signal.

This was a bare shell rebuild and so only the required components were refitted, hence the single abs sensor and no more CANbus or ABS unit etc.

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Most ABS sensors from the era of this car would be a magneto resistive type.  They can be quite tricky to make them output suitable voltages as they actually work by switching between 2 different current levels rather than high/low voltage levels.  You need to experiment with a range of supply voltages and pull-up/pull-down resistor values.  You need to achieve something more than about 2V when high and less than about 1V low.  Have a read of this doc for a bit of guidance: https://www.motec.com.au/filedownload.php/CTN0007 Magneto Resistive Sensors.pdf?docid=3634

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