Maybe someone here can offer some advice on this issue. 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, 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 proove 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....

 

Hi Rons85,
I am currently having the same code 33 after upgrading to a larger throttlebody. I am also driving a 85 vette.
Can you send me the updated definition file so I can fix this problem? email = r.w.tammes@chello.nl

Thanks,
Ronald

 

Don't bother - the code 33 switch now in the updated definition file doesn't really eliminate the code - it just stops some of the code actions, namely the SES and storing the code in memory. The code still happens and the car still drops into limp-in mode.

I found the solution though - edit the MAF "scalar" tables - the conversions from counts to Gm/Sec. Doing That finally stopped the code issues - I pulled that numbers down around 85-100 Gm/Sec and then multiplied the entire set of tables by .90 to flatten the whole curve. It Worked. Still drives fine with no seat-of-the-pants negative results. God only knows what the real result is of lying to it about the airflow, but until I put the thing on a dyno he'll have the knowledge to himself!

BTW - I tried editing the table for Max air flow at RPM - to no avail, the code diagnostic must look at the airflow before the table comes into play...

 

Can you send me the file anyway?
As you probably know the $1F eprom for the 85 corvette is only supported by TC and I don't like to buy the definition file for $20, just for this problem.
The car is costing me enough at me moment..
But if you dont send it, thanks anyway for the information.

Ronald

 

rons85,

I was reading this thread on my lunch break because I have an 85 and I am receiving error codes 32 & 43, as well and wanted to ask some questions from someone who sounds like they have a clue. (at least your statements make sense and they are coherent and don't sound like someone from a foreign country that can't even speak english )
Anyway, my situation is that I have a stock 85 with a block in it that has less than 30K but some of the sensors are old and the CAT has been removed(with plans to replace it) and I've removed the emissions tubing that are soldered into the exhaust manifolds.
This is a pretty sweet running ride(when it runs good) but for now, all I know how to do is pull the codes from the ALDL with a paper clip and change out any bad sensors.
My question to you is: What tools do I need, to allow me to perform scan & tune functions for myself on this vehicle?
I have a friend that does some ODBC II scanning but as I understand it, our 85 Vettes fall into the ODBC I category which limits us to other tools.
Your input is really appreciated.
I like doing things of my own and I've already performed a number of other things on this car but would like to get ramped-up on the scan&toon area to allow me to "run" like I want to.

again, thanks for any input anyone can offer,

85_TPI

 

My question is: What tools do I need, to allow me to perform scan & tune functions for myself on my 85 Vetter (L98 engine)?
I have a friend that does some ODB II scanning but as I understand it, our 85 Vettes fall into the ODB I category which limits us to other tools.

thanks in advance,

85_TPI