Very rough signal from the wideband controller - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 08-31-2012, 12:04 PM   #21
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Just to let you guys know something. I had my wideband previously wired to the ground wire on my MS1 adapter cable. It still had a fair bit of noise, although much better than before. However the MTX-L resetting and failing to sync with the probe became a lot more frequent!

I unwired everything, but since I'm dyno testing my car tomorrow, I figured I'd wire the MTX-L back again temporarily. I wired it back like it was (+12V on IGN from radio and output 1 to the MS input)...

However, because I didn't want to take the protection plate from the footwell, I wired the ground to one of the plate retaining nuts. I figured I'd test it afterwards, and what do you know, the signal oscilations reduced even further!

So if wiring to 2A didn't solve it for you, I'd at least suggest you try this. It's effortless!


Attached are screenshots from the small log I took. You can see it only oscilates between 13.2 and 13.6 roughly, while standing still. The gauge was steady on 13.2 though.

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Very rough signal from the wideband controller-afr_mt_latest.jpg  
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Old 08-31-2012, 12:34 PM   #22
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it needs to ground back to the engine, not the chasis.
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Old 08-31-2012, 03:07 PM   #23
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Widebands with a single ground wire should have it connected to the ECU's power ground pin, not to the engine block.

Widebands with a separate sensor ground wire should have the latter connected to the ECU sensor ground pin, then the power ground wire to the engine block.
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Old 08-31-2012, 03:10 PM   #24
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the ECU grounds back to the engine block does it not? sorry im not a noise cancellation black arts wizard expert like you
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Old 08-31-2012, 03:14 PM   #25
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Quote:
Originally Posted by Braineack View Post
the ECU grounds back to the engine block does it not? sorry im not a noise cancellation black arts wizard expert like you
The ECU has two different grounds, power and sensor end up at different spots. Dont quite remembe which goes where.
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Old 08-31-2012, 03:16 PM   #26
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the sensors pretty much ground back at the ecu, that's the point of a sensor ground, although the miata is not perfect, as they take a few detours and acutally connect to the fuel rail and chasis (under booster) along the way. All the Black/Green wires for sensors connect together and back to the ECU at pins 2C and 2D, but also ground at the fuel rail.

Pins 2A and 2B run from the ECU directly to the....fuel rail.


see page 2: http://www.miataforumz.com/1990-200-...ing/92diag.pdf
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Old 08-31-2012, 03:19 PM   #27
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Thats odd. I expect all the sensor ground wires to go directly back to the ECU and then the ECU has two grounds with the sensor ground and the power ground divorced from each other.
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Old 08-31-2012, 03:25 PM   #28
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That's what you'd expect...
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Old 08-31-2012, 08:21 PM   #29
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Quote:
Originally Posted by Braineack View Post
the ECU grounds back to the engine block does it not? sorry im not a noise cancellation black arts wizard expert like you
Yes but the voltage isn't the same at the end of the wire at the engine end as it is at the ecu end. Picking a ground point has to do with realizing that wires are not perfect conductors.
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Old 08-31-2012, 11:47 PM   #30
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gotcha.
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