ok i got a 94 z28 a few days ago and it has a ses light on. it has the 12 pin diagnostic port and so i tried to flash the codes by connecting the "a" and "b" terminals together, but then when i turn the key the fans come on and everything but no flashin ses light, it just stays off, i know the bulb isnt out because it comes on when i turn the key with no jumper wire. is somthing wrong with my computer? the car also has a pretty bad fuel smell inside the car when i first get in, im not sure if they are related tho but what can that be?

 

That might have worked on your 93 but WILL NOT on 94+ cars which require a real scanner.

 

Actually...the 94 uses OBD I technology and although you can buy a "scan tool" at the store for $25...it does nothing more than connect the two terminals together. It will turn the fans on when the terminals are connected..that is normal. I don't know why you are not getting the SES light to flash a code since you have it illuminated when it is running....

 

it will cycle the LED on the tool, but not the SES light on the dash

 

Yes it is OBD1 BUT as I already covered you need a scanner, one that displays the codes itself because the flashing SES light will not happen. You are however correct that the $25 scanners are little more than the paperclip trick, it just doesn't work on this late version of OBD1.

 

...because 1994 LT1s don't flash codes. Yeah, it's OBD-I like the 1993, but it is a completely different computer. You need a real scanner.

 

Thanks for the good data. I also have a 94 and I have problems that I'm having trouble diagnosing. I've only driven the car (3) times since I bought it and it left me on the side of the road all (3) times. Can I use the harness/software/laptop combo to retrieve the codes on the 94? I never get a SES when mine decides to shutdown.

 

Yes, you can use diagnostic software and cable to monitor your computer.

 

yea thats what i alwayse thought with the 94s, but check out the haynes manual for our cars.... chapter 6, it says u can flash the check engine with a paper clip. imma burn that stupid book, i dont think ive ever fixed one thing using that book where it was truley helpfull

 

wait so the scanners out there just have a light that flashes instead of the ses light? mabe this is a dumb question, but can i just stick my test light in terminal a and b? or do i realy need to go to auto zone and buy a stupid scanner?

 

If you are going to mod the car honestly a laptop is a better option, if you don't have one a cheap OLD $100 200mhz laptop off Ebay is good enough then another $30-90 for a ALDL cable. Then there is one free program called Freescan that works and there is Datamaster which has a 20 recording sessions free then costs like $90, it can play data back just as if the car is driving or you can slow it down so you can see better. Once you try it you will want it. Once you have the laptop and cable you can get pcm tuning software for $90 or professional tuning through email starting about $50. I know all this sounds like a lot BUT it allows you to do so much and allows you to diagnose issues even before they set a SES if you know what the readings should be.

 

In your "old" 93, you could have shorted the A & B terminals to flash the codes on the SES light. You can not do that on your 94.

http://shbox.com/1/dlc2.jpg

The word "scanner" is generic. The Actron you can buy for $30 is nothing more than a switch that shorts out the ALDL pins. You can do the same thing on your 93 with a paperclip. The box for the Actron says it works on 94's. IT DOES NOT. Haynes indicates you can short the pins on the 94. HAYNES IS WRONG.

For 94/95, you need a true OBD-I "scanner".... one that connects to the ALDL port, and reads the data stream from the PCM. There are a few hardware items, like AutoXray, ScanMaster, up-level Actrons, etc. Then there are software systems - Diacom, TTS DataMaster, Freescan, and EFI Live V4. You need a specific cable and a laptop. You can download DataMaster and FreeScan software for free.

94 cable will use the conventional 12-pin OBD-I connector. 95 cable requires a 16-pin OBD-II connector, even though the 95 PCM is OBD-I.

For 96/97 you need OBD-II software or hardware.

 

haha yea i bought the actron one b4 i read that and just realized it dosnt work, imma return it, oviously your rite cuz its not working, the factory 1994 service manual says u can jump the wires too tho which is kinda stupid

 

Just curious, what page says that?

 

page 6E-6 of the second book on the lower left hand side of the page says

"Although it is recommended that a diagnostic scan tool be used to read diagnostic trouble code(s), it may be possible to flash trouble codes on certain vehicles equipped with a 12 pin DLC connector. The DLC connector terminal "B" (diagnostic terminal, if equipped) is the second terminal from the right of the DLC connector's top row. The terminal is grounded by connecting it to terminal "A" (internal ECM/PCM/VCM ground), the terminal to the right of terminal "B" on the top row of the DLC connector"

if you go on to read on the next page it says that the ses light will flash to display the codes. i find it very interesting that the gm geniouses could miss that. oh well looks like ill just have to wait till monday to put a scanner on the car at school.