REVELTRONICS

I have a 1991 Dodge that uses 12V and 5V sensors. The 5V sensors include MAP (3 wires), while the O2 sensor is fed by 12V. The car is turbocharged, so the MAP will see positive pressure. I also want to read data from the vehicle speed and coolant sensors (2 wires each). All of these sensors share a common sensor ground that is not connected to the chassis ground. I'm also adding a wideband O2 controller that will simulate a narrowband sensor.

I've read the documents for the UT Comp Pro, and have questions about grounds:

My car's ECU puts out a 5V reference signal to the MAP sensor, and it is grounded to the sensor ground circuit and has a third wire for signal data to the ECU. That sensor ground circuit is not connected to chassis ground. The coolant sensor has 2 wires, one is the same circuit as the MAP sensor ground and the other goes to the ECU. Same with the speed sensor, 2 wires- a sensor ground and a wire that goes to the ECU and speedometer.

When I wire up the UT Comp Pro, I want to use data from all of these sensors to avoid adding more sensors. While I do see several 5V output pins, I do not see a unique sensor ground circuit on the UT Comp Pro. While I can tap in to the signal data lines, will the UT Comp Pro be able to read the data? Would I connect the car's sensor ground circuit to one of the 18B20 grounds or to the buzzer ground?

To get proper readings you should connect UTCOMP ground (black wires) to the ECU ground (in 99% cases it is vehicle ground). Then, you should connect sensor signal wires to AdcX inputs in UTCOMP.

If your UTCOMP ground is vehicle ground, than you do not have to connect DS18B20 ground from utcomp - you can make shorter connection from near vehicle ground.