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So your check engine light’s on and you have no freakin’ idea what’s wrong.  Is something actually wrong with the engine, or is it just a failed sensor?  If you’re driving an older vehicle — something that’s computerized and built before around 1995 — it’s probably OBD-I, which means two things: 1) You can’t use any of the fancy OBD-II code readers (with LCDs and built-in manuals) to tell what’s up, and 2) you aren’t going to have to spend $200+ on one of the aforementioned readers.

In fact, you can pick up a little “scanner” for arounde $25 that’ll do the job just fine, assuming that you’re patient enough to sit and count LED flashes.

By inserting the OBD-I “scanner” into the plug under the dash, you place the vehicle in “diagnostics mode.”  When you then turn the key to the “on” position, the LED on the front of the device flashes out — in the case of GM vehicles — a series of two-digit codes.  By referencing those codes in the accompanying manual, you can can figure out what the engine’s bitching about.

The code scanner pictured above is manufactured by Actron for use with GM vehicles, and it’s available for sale (under their name as well as a number of others like “Sunpro”) for around $25 online and at most auto parts stores.  OBD-I implementation varies by manufacturer, but similar solutions are available for most other early computerized vehicles.

GM Code Scanner (Model CP9001) [Actron]
Street Pricing [Froogle]


4 Responses to Finds: GM OBD-I Code Scanner

  1. Toolaremia says:

    Save yourself $25 and use a paperclip to short out the appropriate terminals on the ALDL (Assembly Line Diagnostic Link). That’s all this does, but with a switch.

  2. Myself says:

    The pre-OBD interface on my ’86 Renault did the same thing, except the contacts were under the hood. Remove the dust cap, short these two terminals, put the key in run without starting the engine, then count the flashes on a lightbulb connected between these other two terminals. Took me about 2 minutes to scavenge enough alligator clip leads and an appropriate lightbulb.

    OBD-1 is even easier, since it uses the check-engine light. Short the terminals and count the flashes. I’m not sure why the “scanner” even has a built-in LED, except perhaps as a backup in case your check-engine light is burned out. Hit troublecodes.net to figure out what 12-12-12-61 means, and you’re done!

  3. Fletcher says:

    Another vote for the paper clip for OBD-1. I keep a paper clip and a code sheet in my glove box. Cost: Zip.

  4. Old Donn says:

    Got 2 of these, (Ford & GM), back in the days of OBD-1, saved me a load of $$$. Paper clips? Yeah they work, so does rubbing 2 sticks together to start a fire.

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