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Author Topic: Reading Honda MAP sensor without adverse affects?  (Read 776 times)
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Seattle, WA
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Hey everyone, I come from the field of automotive electrical installation and mechanical repair, i am using arduino as my segway into microelectronics and coding!

so, i've already written a few successful sketches, done a little interfacing, but i have a problem.

i have a 1992 Honda Prelude and i wanted to use the arduino to create a little diagnostic information display. i have tapped into the signal wire coming from the manifold absolute pressure sensor (MAP sensor for short) to the ECU and connected it to analog pin 0 (5v input w/ common ground and laptop power supply for arduino) the MAP sensor runs on a 5v supply from the ECU and outputs a varying voltage between ~ 0.3V - 3.0V based on intake manifold vacuum pressure and is used to calculate engine load among other important data points.

The problem is, the engine seems to run/idle rougher and be less responsive when the wire is plugged into the arduino and even worse if the arduino is connected to the MAP wire but the arduino is disconnected from power.

i can only assume this happens because the arduino is throwing the signal off a bit.

So, the question is, WHY exactly does this happen? and WHAT can i do to remedy the problem while still receiving data from the sensor? (what and why are important since im in it for the learning!) make a transistor circuit to boost the signal from the MAP so the arduino and ECU can still use the MAP wire without any signal degradation? i know i could just use a secondary MAP sensor but i would rather learn how to do it right than slap a band-aid on the issue smiley

Any information shared is greatly appreciated! I truly value your expertise and willingness to help others learn!

Manchester (England England)
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Never ever connect a signal to an arduino or any other chip without it being powered, you could fry it.

How is this wired? The analogue input has a very high input impedance so it should not affect the signal. Measure the signal with a scope before and then after it is connected to a powered arduino.

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Any update on this? I'm about to tap into the Throttle Position Sensor (TPS) and Manifold Absolute Pressure sensor (MAP) on my motorbike. I want to be able to do this without messing up the signal and upsetting the original ECU.

Typically the sensors are supplied with 5v from the ECU and outputs 0-5v back to the ECU.

Any ideas?


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