Hi,
Its weekend, time for a new MS issue.

I tried to calibrate my TPS, but it always reads 254.
I changed the wiring and the sensor itself.
Cables are OK and both sensors read the same values.

When I connect the sensor I just get 5V (reading 254) in the MS.
When I ground the MS input from the TPS sensor, I get 0V on the MS.
When I isolate the MS input the voltage builds up slowly, like a capacitor charging.

Any Ideas?
Stefan

 

What year MX-5 is this one? And how did you measure the sensor voltage?

 

I have the same problem, no solution yet. Just curious, you get normal coolant and air temp readings?

 

All other values are OK.

I think I solved it.

I will test it tomorrow and post.
I connected only 2 wires to the TPS sensor.
I did not connect ground.
BUT: in this configuration you get a 5v voltage drop on the power supply (MS), when changing the resistence.
You get different current, but voltage stays constant.

When connecting the ground to the TPS you get a voltage divider and the current stays the same. In this case the voltage changes at the MS.
I think this is the way it should be.

Did you connect these wires to the TPS?

Megsaquirt 5V output?
Megasquirt input (normally the middle pin)
Ground (to MS sensor ground) ?

 

A TPS isn't going to work without a ground. You'll only see 5 volts all the time with this - which appears to be precisely what you're having go wrong.