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CAN Bus Termination: AEM to MS3

 
Old 09-20-2018, 12:29 PM
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Default CAN Bus Termination: AEM to MS3

Gentlemen,
Should I use 120Ohm resistor in parallel with AEM 30-0300 X-Series AFR Gauge connected to MS3Pro PNP to terminate CAN bus?
Please advise

Update:
I have received an answer from Matt Cramer, DIY support:
"The MS3Pro has a 120 ohm resistor at its end. It looks like you'll need to put one on the AEM unit as well.
Matt Cramer.DIYAutoTune Support".

Last edited by irodd; 09-22-2018 at 05:19 PM.
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Old 09-21-2018, 10:49 AM
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Matt Cramer please help

from AEM
30-0300 manual:

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Old 09-21-2018, 11:38 AM
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You don't need the resistor.
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Old 09-21-2018, 11:45 AM
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I read that as needing the 120 Ohm terminating resistor since there is not one internally. Not quite apples to apples, but I am installing an AIM MXS Strada to my MSPNPPro, and I needed to enable the internal 120 Ohm resistor in the software for the MXS.
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Old 09-21-2018, 12:41 PM
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Originally Posted by SpartanSV View Post
You don't need the resistor.
Thank you Spartan!
Do you know the reason why the resistor is not needed?
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Old 09-21-2018, 12:47 PM
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Originally Posted by irodd View Post
Thank you Spartan!
Do you know the reason why the resistor is not needed?
Nope. All I know is that I didn't use one when connecting that exact wideband to my MS3x which is essentially a MS3pro. There's been some discussion lately about running that wideband on the MS3pro and none of those guys mentioned a resistor either.
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Old 09-21-2018, 12:55 PM
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You should add the resistor. It might work without the resistor, but there should be a resistor. You can even buy nice connectorized 120 Ohm termination resistors so you don’t have to mess with soldering stuff into your harness.

DTM termination resistor for $5
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Old 09-21-2018, 01:02 PM
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I have it connected without termination resistor too, and it is still working.
but I believe the termination in CAN Bus networks is for signal quality (and some other reasons).
From my SAAB Can bus expirience - there were lot of bricked ECUs during reflashing via can bus without termination resistor.
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Old 09-21-2018, 03:29 PM
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That's exactly what its for, signal quality. It keeps the end of the CAN run from becoming an antenna, and makes the input impedances play nicely with whatever buffer or I/O chip is in the CAN equipment.
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Old 09-21-2018, 04:10 PM
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I have received an answer from Matt Cramer, DIY support:
"The MS3Pro has a 120 ohm resistor at its end. It looks like you'll need to put one on the AEM unit as well.
Matt Cramer.DIYAutoTune Support".

Last edited by irodd; 09-22-2018 at 05:19 PM.
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