When V1 first came out, there were still a few of these I didn’t quite understand (especially in periphery 0). This area of the code probably took the longest to disassemble and Jeff deserves major credit for his help in tracking down which bits correspond to what CEL.

A few of you guys have issues following instructions so I’ve included notes of what ones to not touch. In this post I’ll go over each periphery in detail and hopefully that’ll clear up any confusion.

Basically, Periphery 0 is just a bit to toggle specific OBD2 functions and Periphery 2 thru 4 just toggle individual Check Engine Lights.

This is Periphery 0:


When you install a flash ECU into your car and/or you want to do a full vac reduction, there aren’t any bits that need to be disabled in this periphery.

The only thing you might want to play with are the Speed Limit Function (bit 6). This enables the safety feature. Handy for when you drop your car off at a shady mechanic and you’re afraid they’re gonna play with your car.

If you want your car to run only on 1 narrowband instead of 2, disable bit 2. This will then make the code function off the rear narrowband only.

If you want to disable closed loop entirely for any reason, switch bit 4 off and the ECU will be in open loop all the time.

Also note that I made mention to not play with bits 11 or 12. This is because they don’t enable/disable the code, they only switch the code to another type of function. Since Mitsu used this ROM in every one of their vehicles, they encoded the functions for all the cars and used these bits to trigger which condition they wanted the system to function under. If you play with these, you’ll find your car will run like ass.

Leaving these as they are and eliminating the solenoids will not hurt anything.

This is Periphery 1:


AKA the Chrome Mods periphery. I took it over as it was all just unused space in memory. I’ve also included a switch bit to disable all the mods at once for diagnostic purposes should you run into issues.

This is Periphery 2 thru 4:


These are all the CELs I could find in the code. Quite literally all you have to do is disable the bit containing the code you don’t wish to see illuminated on your dash.

So when you first install your Flash ECU, you’ll need to disable bits 15, 14, 13, 11, 10, 9, 3 and 1 to ensure no CELs if you’re a 1G car (or any car with a full vac reduction) without any of these systems. Even the 96/97 cars will need to disable bits 13-15 as you guys don’t have the same purge system as the 98/99 cars.

Say you wanted to eliminate the secondary O2 sensors without a CEL. Then all you gotta do is disable bit 3 and 11. See how that works?

Disabling these bits won’t disable their function, only the Check Engine Light!

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