Maybe someone here can offer some advice on this issue. This is not specifically an F-body problem, the car is actually an '85 vette... I dove into editing the eprom file a bit ago trying to eliminate the code 33 MAF error that I started getting after going to a larger throttle body (this is an '85 with a mild cam, OEM TPI, mildly ported heads, no cat, larger MAF, etc..).

The original mask or definition file I had ($1F - using TunerCat ) did not include the switch settings for any of the diagnostic codes. After mentiong to TC what I was trying to do he sent me an Updated file that now Does include switch settings (on / off) for the code 33 MAF, and also the code 43 ESC, code 32 EGR and code 24 VSS.

It appears that the MAF code 33 switch does, indeed, prevent that code from happening - at least I have not been able to make it appear since setting that switch to off, in Several versions of files I have tried so far.

I have doubts about the ESC code 43 switch, however. While experimenting with spark advance I have had the car drop out of normal (closed loop) operation and into Limp-in mode - under fairly heavy load, repeatedly - without turning on the SES or saving a code (nothing on the scan tool after the event). It Acts as if it would be a knock issue - as if it had seen a code 43, but not stored it. I cannot make the thing repeat the fault while monitoring the knock counts with the scan tool....nor does the scan tool (Snap-on MT-2500) display any knock counts under conditions that would cause the event if the scan tool was not connected (in diagnostic mode).

Is it possible that the switched bit is not actually preventing the code from triggering, but is only preventing the "display" of the code event? I'll be playing with identical versions of a program where only the code 43 switch is on or off to try and prove to myself that the triggering event causing the thing to drop into Limp-in is, in fact, the ESC detonation signal. If it is Not that signal (not a code 43) then I'll have to try and figure out what else is going on....

 

The diag. masks prevent the code/error from being set and will also prevent some things associated with the code from being run. For example, no PE SA when code 43 is disabled.