aw2055989

So what's the real story with obtaining error codes on a 1994 Z28 LT1 OBDI system? It's been flashing here and there when i stomp on it, it hesitates and then when i let up it starts running fine. I was told i could jump PINS A&B with a paper clip so i tried that and my SES light does not come on. I was told I couldn't jump anything after 1993 and i needed a scanner so I got one. That hasn't worked either. I looked at the scan tool and it looks like just a fancy housing for what the paper clip does. I've seen a lot of threads in here about the subject but they seem to contradict each other, some say you can jump, some say you can't, some say you actually have to have an OBDII tool with a different cable. The book my scanner came with says if I scan and the SES light doesn't come on then i need to do a Diagnostic Circuit Check as outlined in the GM service manual. Does anyone know the actual correct way to read a code on this car? I'm guessing it's a lean code from the way it's acting, but i'd like to read the code nonetheless. Thanks for any help.

bobdec

aw, Earlier OBD1 ECM's ('93 and earlier chip ECM's) had an error display program internal to the ECM that activated when the ALDL pin was grounded with a paperclip. It displayed the error codes using a sequence of blinking the SES indicator. But the '94 and '95 PCM's are called 'flash' memory PCM's and they require a scan tool with firmware to establish communications with the PCM in order to read the error codes from the PCM memory. So the '94 and '95 F-Body cars are unique in that they need an intelligent scanner for OBD1. This confuses the heck out of most parts places that do free scans. You need to find a place that understands this for your '94 setup and has the correct scanner. Otherwise odds are 100% they will use the incorrect OBD1 scanner and then erroneously tell you the PCM wont communicate and you have a problem..

moparman

'93 was the last year the pins could be shorted to read the codes. '94 and up require a code reader or scan tool. Unfortunately, the cheap code readers, as you found out, do short the pins, therefore they won't work on the '94 and up. It's also getting hard to find an OBDI code reader or scan tool, as all vehicles, since '96, are OBDII. There are lots of scan tools that do both protocols. I have an Auto Xray that does both, and came with the necessary cables, including one for the "tricky" '95. If you buy a scan tool, be sure it has the proper cables. Check Amazon for scan tools.

aw2055989

ok, well i stopped by autozone (only place in area to do free scans) and they said they couldn't scan a 94 because the company took their cables. they said i had to have a scanner and sold me what amounts to a $30 paper clip holder. looks like i'll try to return it and go to shop that has the right equipment. thanks for the info.

Injuneer

That's the Actron CP9001... basically a 1-cent paperclip in a $30 box. It says on the outside of the box it will work with a 94, but that is not correct, as described in posts above. Even the 94 factory shop manual indicates some 94's can be read by shorting the ALDL pins, and that is also incorrect.

There is scanning software (DataMaster) available from TTS Powersystems. Free download, 20 free uses before it asks for you to buy a license. Not only tells you the codes, but allows you to data log the PCM while driving. Invaluable for helping to diagnose problems. Just need a data cable to connect a laptop to the ALDL connector.

TTS Power Systems

There is also "Freescan", which used to be free, but now has a small cost to help pay for upgrading it to more recent Windows versions.

And if you can find someone with an Actron CP 9145 OBD-1/OBD-2 scanner, it will work on the 94/95 if they have the optional OBD-1 cables/adapters. Many other newer OBD-1/OBD-2 scanners will not work on the 94/95 because they are looking for a 12V pin in the ALDL connector, and there is none.