OBD II Mil/Test Switches

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Rich A
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OBD II Mil/Test Switches

Post by Rich A » Fri May 26, 2017 6:52 pm

Where can I find info on the OBD II Mil/Test Switches, What does the numbers mean?
The factory readings are 247 Mil and 183 test, but they now both read 18.

Rich A
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Re: OBD II Mil/Test Switches

Post by Rich A » Tue Jul 11, 2017 1:54 pm

http://www.snipertuningforums.com/viewt ... 56c4a0f534
almost the same question but my question is more specific.

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Sniper Chris
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Re: OBD II Mil/Test Switches

Post by Sniper Chris » Thu Jul 13, 2017 10:21 am

This is a difficult subject so I'll do my best explaining with cliff notes.
There are "basically" 8 OBDII tests. Catalyst monitor, comprehensive component monitor, purge monitor, secondary air monitor, fuel monitor, ego monitor, egr monitor and misfire monitor. Each monitor is assigned a bit within a byte. By looking at these various bits you can tell what tests are enabled and what tests have completed.

For the OBDII tests each is assigned a bit. The following is what is associated with what.
Bit 0 catalyst monitor
Bit 1 comprehensive component monitor
Bit 2 purge monitor
Bit 3 secondary air monitor
Bit 4 fuel monitor
Bit 5 ego monitor
Bit 6 egr monitor
Bit 7 misfire monitor

The attached image shows you the engineering unit. This is what makes up the 247, 183 & 18 numbers that you mentioned. So, as you can see in the image, when these 8 OBDII tests are added up you get the value of 255. When a test is "turned off" then that value needs to be subtracted from the total. For example, if you were to turn off the egr then the OBDII Test Switch value would need to be changed to 191 (255-64=191). Keep in mind you more than likely will not see a stock vehicle with the value 255 because more than likely the manufacturer will already have something turned off (for example 05+ Mustang does not have egr). But what ever your stock value shows, you will need to subtract the engineering unit value from it.

That's it in a nut shell. I hope it was clear.
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OBDII engineering unit.jpg
OBDII engineering unit fron Sniper, Inc.
OBDII engineering unit.jpg (175.58 KiB) Viewed 860 times
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Rich A
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Re: OBD II Mil/Test Switches

Post by Rich A » Sun Jul 16, 2017 5:55 pm

That's it. Thanks!
Is there a way to add this to the OBD II Mil/Test Switches notes on the Commando software?

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Sniper Chris
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Re: OBD II Mil/Test Switches

Post by Sniper Chris » Mon Jul 17, 2017 10:46 am

Unfortunately we're not able to add that to the note section.
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