Welcome to knock module hell
 

I'm having issues getting my knock module on my MS3X working. It constantly reads 2.4% whether the sensor is plugged in or not.

My setup:

• MS3X w/ knock module (recently upgraded from a v3 MS2) built using trubokitty.com.
• 90 Miata with JDM 05 VVT engine (turbo'ed of course)

What I have done:

• Replaced the knock sensor
• Checked for continuity from knock sensor plug to K1 on internal knock module (using SPR3)
• Checked continuity of other pin of knock sensor plug grounded on ecu plug ground.
• Resoldered the connections from the knock module to MS3 daughtercard
• Checked continuity from PM2 to knock module
• Replaced c6 and c7 on the knock sensor module (I was seeing 2.5v on the south side of the caps, but not on the sensor side.) I thought that was the issue. :/
• Beat my head against the wall.
• Said F^%&k it and started tuning the car without the extra safety.

I have been able to get the knock module to respond by playing a 6.940khz frequency in to it K1 from my laptop headphone jack.

Questions I am still struggling with:

• Is there supposed to be a bias voltage on K1 and K2?
• What am I missing?

Thanks in advance for visiting hell.