I have read many posts here that discuss tapping the OEM TPS output (green/blk wire on a NB2) signal for Aim and other data acquisition systems (w and w/o 1000ohm resistors). I have been constructing a DIY data acquisition system. All works (RPM, brake and oil pressure, temp, etc.). The last circuit I'm working on is the TPS.
I tapped the line and measured it with voltmeter to confirm range of output (about .6 to 3.7V). Next, I used an OBDII reader to see range from PCM. First surprise - it reads 11% idle to 76% full. Holy s!!! I must be down on power!! Swap out a spare and it's the same - tested by both hand at TPS and pedal. Sigh of relief upon determining it's normal and I keep going.
I attached the TPS signal to my system (see below for description of system). My system apparently changes the load and signal the PCM sees and the TPS range from the OBDII is now 5% to 58%.
Question: Does this impact on PCM TPS readings happen when connecting to Aim, Traqmate, etc.? I also read online that the PCM reads the differential of idle to full open, not absolute, so 5% to 58% could work as well as 11% to 76% if this is true. Any info on this? I would have driven the car to directly test this idea but live in a very well patrolled town.
I used a STM32 "blue pill" microcontroller. It is interconnected with a 9 axis accelerometer/gyro/magnetometer chip. The STM32 interfaces with a bluetooth transmitter chip to send data to a phone or tablet for logging. GPS can come from the phone, an external bluetooth GPS or a dedicated GPS connected to the system. I have brake and oil pressure signals from dedicated sensors. I tapped the instrument cluster temp gauge wire for temp signal (this sensor/signal is independent of temp sensor for PCM and doesn't impact PCM). RPM signal is also from cluster. This is about $20 of chips from Amazon. The whole thing will cost about the same as an Aim brake pressure sensor when done.
This has been a good project while I'm being socially distant.