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Sensor Grounds (5V and 12v Sensors, speed sensors, knock....ETC))

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Hey guys.

I have some questions for my ECU (NS15+). I read and I need to keep my 12v sensors (Flex Fuel,sr20 CAM sensor) off of the sensor ground on the ecu and to ground those sensors to the engine ground. I read to only keep 5v sensors on the sensor grounds. I was also told to keep my speed sensor (stock s14 2 wire speed sensor) and knock sensor to engine ground. but i was also told different that i can wire my 12v sensors to sensor ground on the ECU.

My questions are

Can i add my cam and flex fuel grounds to sensor ground even if they are 12v?

Can i use sensor grounds for my Speed sensor and knock sensor?

thank you in advance!

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You can connect both 5v and 12v sensors (and VR sensors etc that have varying voltage output) all to the same sensor ground. 

The reason to chose 1 type of ground over another is not input voltage, but more:

1) how stable does the signal need to be for the engine to run well (crank trigger = really important, any of the temp sensors = not a big issue if the signal bounces around a few percent). And as part of this, will a ground offset cause an incorrect reading that still looks legit. (eg voltage offset on any analog sensor)

2) How much load is expected to go through the ground circuit. eg do not use a sensor ground as the ground side for a vtec solenoid or anything like that.

As long as everything on the sensor grounds is low *current* then adding a flex fuel sensor to sensor ground wouldnt hurt, and generally anything that is an ECU *input* you would lean towards putting on the sensor ground circuits. But if you do see issues that seem like sensor noise once you add it, you can probably move the flex sensor to use a direct ground and not see too many issues. These dont report an analog output anyway so should work just fine with slightly noisy voltage/ground.

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