I would like to cross reference the 12 pin to the 16 pin. This way, I can still attach a 12 pin cable, and the data be read. The reason? CA Emissions... they may have a cow if the wrong cable is used.

 

Don't let it be a factor. Cali doesn't touch the connector for a smog test. Only obd2 to check readiness status.

 

94s are partially OBD-II compliant. They have some of the OBD-II codes.

The rear O2 is not a dummy. [rant]This is one of the dumber myths perpetuated on this board. Like GM would spend the money to put an unused O2 on 45000 cars. [/rant]

Highly unlikely an emissions tech is going to notice the MAF and realize it's changed.

Gas mileage is 16/25 for a 92 6sp and 17/25 for a 95 6sp. You're gonna have to drive a lot of miles for that hypothetical 1mpg city to repay the time and money the conversion will cost.

One reference you might want to get is "Corvette Fuel Injection" by Probst. It shows the differences between the years and has the schematics for both.

If you need any info off a 94 down the line, let me know.

 

Steve, you can say that without telling us what it does on a 94?

 

As far as I can tell it doesn't do anything. You can monitor its status with a TECH2 but if you disconnect it no codes will ever set. Mine has been disconnected since I installed the EM headers. So far no issues with it being gone. It was a pre-OBD2 device from what I understand but why it put in I have no idea.

 

It does exactly the same thing it does on any other OBDII car, monitors the cats.

There are about 20 more O2 sensor codes in the 94 vs the 93, along with a bunch of other OBDII codes, maybe 100. I don't have the manual here so those are rough estimates.

The OBDII codes do not set an SES light, and they require a different procedure to read on the TECH than the OBDI codes. Not setting an SES light is not remotely the same as "doesn't do anything."


This information is available in the shop manual, in the book I mentioned above, and on the web.

 

I have Charlie's book. So I will review that.

 

Steve, I am not sure where your information is coming from. But I have all the MALF bits mapped in my PCM tuning software via a code disassembly. And I can tell you that in a 94/95 PCM there are only 6 O2 sensor DTCs. They are, DTC13 Open B1 sensor, DTC44 Bank 1 sensor lean, DTC45 Bank 1 sensor rich, DTC 63, 64 and 65 for Bank 2 sensor. There are no DTCs that has been found in the disassembly to map the failure of the rear 02. Now it may sit there and monitor the CAT, but there isn't a DTC for it, and with it gone, none will set. And with it disconnect there has been no known ill effects. If there is a MALF bit being set whether its lights the SES light or not, the TECH2 scan tool will record it.

I agree in OBD2 strategies there are many more DTCs associated with O2 sensors. In the OBD2 cars, there are several parameters that are monitored by the PCM that are not done in any pre-OBD2 strategy with the 94/95 B, F and Y LTx cars inclusive.

Sensor switching, heater circuits, sensor activity, low and high sensor output voltages just to name the main ones. Believe me I have gone through this mess of O2 sensor DTC's as I have been fighting a sensor related problem in a 01 C5 for the last couple of days. This is after having to get this car after some so called tuner got a hold of it. I finally think that the problem is solved

 

You might want to reread my prior posts then.

O2S DTCs from the 94 Shop Manual:

13
44
45
63
64
65
P0131
P0132
P0133
P0134
P0135
P0151
P0152
P0153
P0154
P0155
P0158
P0160
P0161
P1133
P1153
P1158

I was way off on the overall OBD2 count. There are only about 10 non-oxygen sensor OBD2 DTCs listed.

Not setting an SES is not the same as doing nothing. (I swear I heard that somewhere before.)

 

This DTC that there isn't one of and doesn't get set is DTC P0420.

 

The P999 codes were OBDII codes? Why are they on 1994? That's still OBDI?

I need a 1994 service manual... and read that book.

I will say one thing about Charlie's book, it has some errors. Charlie died during final editing, and I don't know how effective they were at fact checking.

 

My understanding is the third O2 sensor is to just let the computer know after in closed loop that that the cats are ready and up to tempeture.
I have only changed 2 out of the 3 on mine with no affects.
When I use the datamaster program no info on the 3 O2.

 

Hey bogus, have you seen this?

http://www.painlessperformance.com/w...erfectharn.htm

Painless has a new PERFECT ecu. I was looking into your idea of bolting on a '96 ECU and updating the harness along the way. Not sure if it's sequential injection, but I have an email into tech right now. The tuning software isn't finished but the tech I've been emailing says its coming. A later harness is about $500 FYI.

 

It is a GM MEFI4 or possibly a MEFI3 controller which is the same as a GM Ramjet engine controller. These are used on their GM power plants as well as their industrial engine lines. There is no known aftermarket tuning software available. GMPT WILL NOT sell or release their proprietary software for these controllers unless you sign an agreement and buy at least 100 controllers. Beleive me I tried getting it. But I finally got a copy along with a CD full of information, I won't say where I got it but I can say that a group of GMPT engineers made this software, and it was made for their calibration engineers. It is very cryptic, hard to use and is not for the average Joe. For example to if you change injector size, you need to change the complete fuel map for all RPM ranges. Where now we just change one or just a few constants depending on what PCM or ECM you are tuning. It is no where near what Tuner Cat offers or what is available to the general public from other tuner programming vendors.

I doubt that Painless will ever offer a tuning package for this. Unless they develope a completely new package for tuning these controllers. They had to sign a confidentiality agreement with GMPT to NEVER sell, give away or otherwise compromise this software. Another group was looking into doing this but its been months and so far NOTHING. I got email from the guy and he finally told me that if I wanted the MEFI software now I would have to purchase 50 controllers! Even if Painless was to offer something I think it would be very limited to what you can edit. I expect that they will limit you to making minor adjustments on timing, idle and some fuel parameters. If they do it at all. I spoke with their engineers at SEMA this year and they told me it was a to be a stand alone system alone without any software for addition 3rd party tuning.

While the MEFI has a lot of power to do a lot of engine parameters. It is still archaic in the way it handles certain things. For example, it can control CNP (coil near plug) ignition so that means it can control 8 separate coils on an LS1. But it only has 2 injector drivers so that means it can only handle bank to bank EFI Now it does have a a few discrete IO points so you can control fans, and other relay devices. I can also do drive by wire throttle control with the addition of a GM TAC module. It can also look at two O2 sensors but it does not have wide band capabilities. The best part is that all of this power comes in a very small package, which is ideal for the hot rod show car types.

 

Thanks for crushing all my dreams! Sounds like bogus was on to something with using a later LTx GM ECM then.

So this may be moronic but what about adapting an LS1 ECM to an LT1? I assume you would have to swap sensors, is the throttle by wire adaptable? I hear they can cope better with mods etc.

 

Well not quite.....but you can take a late model 1996 thru 1999 350 Vortec truck engine and use a 2000 LS1 PCM. This means that you can stroke a late model truck block, use a super ram and using the correct cam and crank sensor direct from any GM parts house you can have sequential EFI and use a LS1 PCM from a 2000 series GM Truck.