I am a novice with regard to electrical circuitry, and am in search of a potential solution for something that spans across the automotive/electrical engineering universe. I am working on an engine with a supercharger, and would like to have an intake air temperature sensor before the supercharger and one after. I have a 12v switched DC output that can turn on and off as compression in the intake manifold (boost) is detected. When not in boost I would like the Engine computer (ECU) to see the pre-supercharger sensor input (sensor 1), while in boost I would like to to see the post-supercharger sensor input (sensor 2). The engine management system from the factory comes with only 1 intake temp sensor circuit.

Its normal configuration is as follows:

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The intake air temperature sensor circuit is 5V, the sensor itself is a thermistor that increases/decreases in resistance as the temperature it reads changes. I would like to add a second sensor to the circuit, and be able to choose which sensor circuit is active based on the presence of 12V DC going into a relay

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Is there a type of relay and circuit that I can build that would support such functionality? Thanks!

Datasheet for sensor:

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  • \$\begingroup\$ To answer this question properly, it's best to have more information about the sensor outputs. Are they analogue (any voltage between 0V and 12V) or digital (high +12 or low 0V)? If digital, is the output open-collector (or open-drain)? If you can't answer these, then we can help if you give us a link to the sensor datasheet. \$\endgroup\$ Apr 14, 2023 at 6:16
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    \$\begingroup\$ You don't need to switch the Ground signals via relay, just connect them all together. There may be a problem during the time the relay needs to switch. During this time, expect 3-15 ms, the ECU might detect a missing sensor. This may or may not produce an error event in the system. You can try that with any 12 V SPDT relay. If the switching time causes problems, you can use an analog switch IC where the switching time is micro seconds only. A sensor datasheet would help to select an IC. \$\endgroup\$
    – Jens
    Apr 14, 2023 at 14:10
  • \$\begingroup\$ Thank you Simon and Jens for your feedback! I've located a datasheet for the sensor and added it to my original post. \$\endgroup\$
    – DT_30
    Apr 14, 2023 at 14:52


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