Car has been running fine for ~1year with minimal calibration or wiring chances.
So I'm driving along all happy one day and then the engine cuts out...

Got the car back home and plugged in the laptop for diagnostics, turns out I have a sync issue. I am running the original 1.6litre CAS only into a MSPNP2 ecu.

I suspected there could be oil in the CAS so inspected it and cleaned it out with some brake cleaner - nothing looked visually wrong with it anyway.

I did a bit of reading on what the CAS signal should look like and got my oscilloscope out and back pined the whole CAS connector, cranked it over (coils were unplugged), see the image below:

The signals I get from my oscilloscope when I back pin the CAS. Problems: Crank is at 12V - should be at 5v CAM is at 5V but has no drop 12v has weird occasional mini drops which are audible.

I thought the 12v could be coming from some fretted wires on the loom, I had no continuity between the (white) crank wire and 12v source. So then de-pinned the connector at the ECU and measured 12volts coming out of pin 2E on the ECU.

So I have isolated the problem back to the ECU. and found another post about the same issue: https://forum.miata.net/vb/showthread.php?t=652271
I've tried reverting to an earlier Cal then going back and it didn't work for me.
Anyone know what has actually gone wrong inside the ECU - anyone know how I can fix this - any mega-squirt specialists in the UK?


The signal on the right shows what the CAS output signal should look like. the ECU pinout with CAS inputs is cicled on the left.

I disconnected the crank pin (2E) from the ecu and put a wire in there so I could measure the voltage straight out the ecu without the loom, it measured 12v...

 

The pullup voltage is irrelevant. Looks like your CAS is dead.

 

Why do you say the pull up voltage is irrelevant?
I thought it had to be 5v on the crank and cam pins that go to the CAS - then the teeth passing the sensor in the CAS pull it down to 0v?

Also I have got the CAS out of the car now and I am going to see if I can bench test it with the scope once I have a 12 and 5 volt source setup.