I've got a '96 GMC with ABS out to lunch. Turns out, the AutoXray scanner I was using doesn't speak 'B' codes. I started shopping for one that does which I can also use for my Corvette, and the plot thickens...

Depending on the source, the story I get is OBD-II started with GM in 1995, and legislatively forced into adoption by other manufacturers in 1996. I've read that Corvettes do OBD-II starting in 1994, except the LT5. :crazy:

Start with the different code libraries, add different connectors and data transmission mediums and this whole thing becomes a freakin' mess. The best information I can gather tells me that the scanner I want is the Vetronix Tech-1A, supposedly available at NAPA or MAC Tools, but it doesn't show up on either website.

Can anybody tell me

A) If the 1994 LT1 has OBD-II

B) What the best OBD-II scanner is for the buck that does other than 'P' codes (Tech-1A rumored at $1500 but I can't find the fargin' thing) or does OBD-I too if my Corvette needs it.

C) Is there an online resource that lays all this crap out? I live with this kind of nonsense from 9 to 5, ain't got time to reverse-engineer another 'standard'.

Any input is greatly appreciated. :yesnod:


[Modified by rocketfinger, 5:40 AM 2/16/2002]


[Modified by rocketfinger, 5:48 AM 2/16/2002]

 

Let's get a few things out of the way first. GM went to OBDII across the board in '96(because of the law), the did have an S-10 Blaser that had it come out in '95. The Corvette started in '96, now the Corvette did go to the 16 pin OBDII ALDL connector in '94 but it was not a true OBDII system it was a OBDI with a partial OBDII system add also, it was a test bed for GM. Every time a Corvette can into some shopes(don't know if all shops were required to do this) for service for what ever the car was to be hooked up to a Cams mechine so GM can pull data from the ECM so as to see how the system was working. Now if a OBDII code were to set it would not turn a service engine light on or cause any change in the running or operation of the car, only if a OBDI code would set would the SES light come on. I do think only a Tech 1 or 1A with a GM mass cartrage in it would be able to go in and read OBDII codes in a 94 or 95.
Now as for scan tools that would be of help for you I would guess a used Tech1 with all the cartrages would be the best(seeing how only GM dealers were able to get a MASS cartrage) but you would also need all the different connectors, but if you did you would be able to work on all GM cars and all the systems and by-dirictional ! Now anothere one to look at is a used Snap-on scanner that should do engine, trans and brakes. Another choies would be MPIS scanner which with the latest GM cartrage would give you engine, trans, brakes and body. OTC also makes a scanner but I don not know all that it does. Anyone of theise scanners new go from between $1,000.00 and $2,000.00, but that is what you would need if you want to do engine pluse other systems. Just about all less expensive scanners will only do just brakes or just engine, don't know of any inexpensive scanner that does all except a used one.

David Fulcher

 

Yup .. listen to David, he knows his ECM/PCM stuff. '94 and '95's are OBD-I .. They have EEPROM's (flashable roms - two of them). You can use OBD-I tools with them using the correct 16pin ALDL connector.


[Modified by Glock'94, 12:59 AM 2/16/2002]

 

Thanks for the 411, David

I guess I'm off to find a scanner. I can definitely see a value in being able to read OBD-II codes off my 94, even if they're not acted upon directly by the PCM. Tech-1A seems to be the logical choice.

I have read a little about bi-directional functionality on some scanners, what I think I'm hearing is that you can adjust engine parameters in sort of a 'diagnostic' mode, but they revert to their original values once the scan tool is taken off-line.

Not to open another can of worms, but a scanner that would allow me to write new parameters to the EEPROM would be handy, starting with the cooling fan 'on' temp...all kinds of bad ideas are starting to form... :reddevil