diagnostic codes

[Cool_The_Slain]

Is it possible to read codes off of a 94 without taking it to the dealer? I went to autozone to have them read it, but they said that only the dealer could read 94 and 95 GM cars because it was some weird hybrid of diagnostic systems and you need some kind of special machine to link up.

[quantum110]

Yeah they need a scanner that can scan ODB-II cars...You shouldn't have to go to the dealer, in fact last time I was in an Autozone they had a display to sell personal ODB-II scanners.

[bwawuz02]

if you go to autozone they should be able to read it. i think the OBD-II scanners will work with the OBD-1.5 system, but don't quote me.

[Zonewizard]

reading trouble codes

Greetings...I am from Mobile, AL and my coworkers call me "the Wizard" because I tend to have a photographic memory and don't forget too much about car problems. I work at Autozone here, and I am in charge of the inventory for eight stores in our area and another in MS.

I can assure you that Autozone DOES in fact have the equipment to determine your 1994 engine codes. The OBD II codescanner retails for about $150 if you really want to buy one, or the store should have one available to test your system for you for free. However, if this is not the correct piece of equipment, fear not! There are a few questions regarding your ALDL (assembly line diagnostic link) to determine if the OBD II is appropriate. First, locate the ALDL under the dash (usually right where your left knee would impact if you were in a wreck) and determine if it is a rectangle or a trapezoid. If it is a trapezoid, then the OBD II is the appropriate tool for the job. If it is rectangular, then look at all the corner sections and see where the two slots are side-by-side that contain a metal link. Once you see them, follow this procedure.

1. get a paperclip or piece of jumper wire.
2. take your keys and put them on the seat so they are not by the ignition switch (just for precautionary reasons).
3. insert the paperclip/jumper wire into the two slots to connect them.
4. insert your key into ignition switch.
5. turn ignition switch until only the warning lights on the dash light up and look at your service engine soon/check engine light which should begin flashing after three seconds. DO NOT START THE ENGINE!!!
6. count the number of flashes to determine the engine code. The first code will ALWAYS be a Code 12 (demonstrated by a flash, a one second pause and then two more flashes), and each code is repeated three times before advancing to the next code.
7. just watch the light as the codes display the first time to be sure that you understand what the number of the codes are. The codes will continue to loop back around to 12 and repeat. After the codes begin to repeat, write them down.
8. once you have written the codes down, turn off the ignition switch and put your keys in your pocket.
9. remove the paperclip/jumper wire from the ALDL.
10. call Autozone to get the code meanings and use these as a starting point for solving the problem.
11. disconnecting the negative battery cable for 30 seconds is used to clear the codes, but should only be done after checking/replacing the parts affiliated with the trouble codes.

I hope this information helped. If there are any other questions regarding this, feel free to let me know.

"The Wizard"

[Cliff8928]

The OBD "1.5" system in alot of the 94 and 95s usually can usually not be scanned by the CP1935 Actron OBDII scanner that AutoZone has... although, if the store happens to have the CP9145 scanner (the one that does all the OBD I and OBD II systems) it should work, But I haven't seen a store that has actually used one of those for in-store use....

Cliff Scott <-also works for AutoZone
89 BerettaGT
89 Volvo740

[Cool_The_Slain]

Damn, having a 94 sucks... nothing works for it, can't get a chip, can't easily read codes... Anyway, is there a cheaper scanner that will work with it than the CP9145? I don't really feel like spending $250 - $300 ($278 @ advance, couldn't pull up the autozone page) on a scanner that I probably won't use that much.

[Cliff8928]

get in good with a service tech at the dealer?!

Cliff Scott
89 BerettaGT
89 Volvo740

[Cool_The_Slain]

Ok, I'm still confused, this is what my connector looks like

According to my book this is an ALDL connector, which is the type that you can short out to read the codes. However, as you can see it only has 3 of the pins in it as opposed to the diagram in my book which has 8. It seems that I only have the ground pin, the serial data pin, and a pin that is not labeled in my book. I don't have the diagnostic terminal that you are supposed to ground. As for reading it with and OBD II scanner, from what I understand, that would use a 16 pin DLC connector, which I do not have. Do some OBD II cables fit an ALDL connector? As for what zonewizard said, it sounded like you could just short any 2 pins that were right next to each other, so in my case, the two on the far right. Is this correct or would that fry something?

[Cliff8928]

This is the basic OBD II connector..



This is the GM ALDL Connector (OBD I)



Cliff Scott
89 BerettaGT
89 Volvo740

[Cool_The_Slain]

So basically I need an OBD II reader with an OBD I Connector?