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Determining which wire/connection from just one end

EFI Wiring Fundamentals

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Discussion and questions related to the course Motorsport Wiring Fundamentals

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I have Haltech Elite SPI3 configured for a speed sensor. I've changed transmission types and I'm trying to verify which plug/wire in the plug is SPI3 verses the ground. I curious if the ECU can place a signal on the wire that I can detect with a volt meter, or if I could do something like ground the wire or place a low voltage on the wire and do logging in the ECU to allow verification of which wire to SPI3. I ask as I don't want to contort my old body into the foot well to get the to ECU plug to verify the connection that way. In general is this, or anything similar, possible for this and other signal wire types? Thanks.

You can ground one of the wire at the sensor plug end and check for a ground on the continuity tester at the SPI3 input. If you have continuity, the wire you previously grounded is the one. Or you can do the opposite and unplug the ECU connector and ground the SPI3 pin. Then probe your speed sensor for ground.

I actualy don’t think polarity would matter on a 2 wire VR sensor used for speed output anyway.

Finally, I don’t think the ECU could output a signal from an input pin via the software, but I have only limited experience with Haltech!