I did some testing with the multimeter today on the signal wire and the power supply wire.

As before I have +5V and a ground. However, as soon as that connector touches the sensor I instantly loose the +5V on the power feed and it doesn't come back until I cycle the key off-on. I repeated this several times with the same result.

I also checked the signal wire while I was connecting the connector and I would get a brief voltage spike on the signal wire up to +0.2-0.3V when the connector touched the sensor and then it would go back to ~0. Obviously this is outside of the normal +0.5V-1.5V but I'm not sure I understand why the power feed line drops to 0 as soon as the connector makes contact with the the sensor. If I start the car with the sensor already connected I can't measure any voltage on the power feed wire.

I also tried the same thing by jumping the connector power feed to the sensor with the ground pin on the sensor grounded and my multimeter on the signal pin. I ended up with the same result where I lost the +5V power feed as soon as it touched the pressure sensor.

Does this make any sense? To me, this makes me thing something is up with the pressure sensor...

To further complicate things after autocross today the ACD system was working for around an hour (~10 key cycles), which is only the second time it's worked since I've owned it (~1000 miles) and by far the longest that it has worked. However after parking for a few minutes and entering a store the system was dead.

Any thoughts?

 

I went ahead and replaced the pressure sensor with a used replacement and this instantly turned off two lights.

They have been off for a few days now and let's hope they stay off.