Success, both oil temp and pressure are working as expected now.
TLDR: Move the oil sensor ground to sensor ground instead of normal ground
I talked to Gerald and he agreed with my grounding idea, so I made a list of grounds at the junction box, as shown left to right:
1. VTC solenoid / oil sensor
2. Crank position sensor / VTEC solenoid
3. Both cam position sensors
4. Ground ring, back of head
5. Coil 2
6. Coil 4
7. Coil 3
8. Coil 1
9. Ground ring, front of head
10. AC1 pin 44
11. AC1 pin 40
12. AC1 pin 37
I decided the cleanest way would be to add a new sensor ground junction box, so I bought:
1x
https://www.corsa-technic.com/item.php?item_id=1697
1x
https://www.corsa-technic.com/item.php?item_id=1698
10x
https://www.corsa-technic.com/item.php?item_id=1104
10x (bought spares / expansion later)
https://www.corsa-technic.com/item.php?item_id=698
1x
https://www.corsa-technic.com/item.php?item_id=381
1x
https://www.corsa-technic.com/item.php?item_id=291
Depinned ground junction box pin 1, cut off the second wire, pinned the VTC solenoid into the existing junction box, pinned the oil sensor into the new junction box (sensor junction box)
Depinned AC1 pin 34, cut one of the wires, pinned it into the new sensor junction box, soldered/heatshrank a new wire from the wire I cut on AC1 to the sensor junction box.
Nice thing is the junction boxes clip together to keep everything tidy. I think a cleaner way would be to crimp a new pin for AC1 instead of splicing, but whatever. I also intend to move the cam sensors and crank sensor to my sensor junction box since Haltech expects them to be sensor grounded.
This is an improperly working sensor graph (green line, bottom graph)
This is what a working sensor graph looks like (green line, bottom graph)
