01-26-2012, 06:57 AM
Join Date: Apr 2010
Total Cats: 0
Heres a copy from the mspnp manual:
Wiring up a potentiometer type TPS
The stock switch-type throttle position sensor does not provide very much useful information to MegaSquirt, so it is not connected. If you want to modify the MSPNP to use a potentiometer type TPS, here’s what you need.
First, remove the TPS stabilizer resistors, R6 and R7. These are the "through-hole" resistors on the daughter board, not the surface mount R6 and R7 resistors on the V3.57 daughter board. Then you will need to connect the TPS signal and reference wires to the Miata harness. There are four holes that access pins on the Miata connector on the underside of the MSPNP board. Solder a jumper from the 5V VREF hole to 1N, and another jumper from the TPS hole to the 2L hole. This will bring the MegaSquirt’s connections out to the Miata wiring harness.
At the throttle position switch plug, you will have three wires. If you have modified the MSPNP as described, the red will supply a 5 volt reference voltage, the green and white wire will take the signal back to the MegaSquirt, and the black and green wire will provide a ground.
If you’re not sure which connection on your TPS goes to which wire, check it with an ohmmeter. Observe the resistance as the throttle opens and closes. Each pair of pins will behave differently:
The resistance between the 5 volt and ground pins will remain constant.
The resistance between the ground and signal pins will be low with the throttle closed and high with the throttle wide open.
The resistance between the 5 volt and signal pins will be high with the throttle closed and low with the throttle wide open.
Using these rules, you can establish which pin on the TPS goes to which wire.
That should sort you out.