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  1. #1

    Question OBD 1 code: 18, crank or cam sensor error, usual causes/fixes?

    Truck: 1990 GMC K1500 SLE 350 (5.7). Original engine replaced fall of 2002 with new 350 GM crate motor. During the past 6 months, the 18 code has appeared a couple of times, to be cleared by disconnecting the battery for a bit. Within the past week, the code has re-appeared 3 times, so I'm thinking it's time to get serious about the fix. The truck is stock, runs great, and breezes through the local smog check with what have been called exceptional values by the testers.

    The answers/opinions found on the internet have pretty much just been confusing, so I am hoping to find an answer here as I still do enjoy working on it myself.

    Many thanks for taking a look!


  2. #2


    Code 18 is darned peculiar, given that it doesn't have either a cam or crank sensor. I can't even find a listing for it in a Haynes book or online. Are you absolutely sure it's code 18?

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