Old FM Miata link scope request
 

Hi guys,
it's really hard to find the old FM link intake air temp sensor in the UK and I've got a broken one here. Won't allow boost due to temp reading 100°. I know the sensor is pwm so I've knocked up an Arduino to take a thermistor, then a pwm output wired in to the ecu.

What I need to know if anyone has a working one and a scope is exactly what signal the sensor gives.

I've tried all kinds of frequencies at a steady pulse and can get a good reading for about 10-30 seconds. After that its like it spots there's a fault and won't recover without power cycling the ecu.

So it's now become beyond me to create a square wave at a trial and error attempt but with no access to a working sensor I can't figure out the pattern... So I'm beat :(

But this is where you might be able to help. If someone can scope a working sensor at a stable temp. Look for frequency, duty cycle... Check sensor resistance too and then look for any abnormalities in the scope pattern over a minute long period. Is there maybe a programmed change of pulse every 30 seconds to tell the ECU all is good? Anything that looks odd.

Then try changing the temperature and note what changes in the pwm signal.

I've started a GitHub repo.. very early stage where I'll share what I create and if we get it working then even better still :)

Hopefull that we can together make a useful service item for some of the older setups.