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

Discussion in 'Chevy C/K Truck Forum' started by steve47, Jul 17, 2013.

  1. steve47

    steve47 New Member

    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. Chris Miller

    Chris Miller Rockstar 100 Posts

    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?
  3. steve47

    steve47 New Member

    Still a mystery. I finally gave up in the quest for the answer ... even local mechs had no clue.

    Many thanks for your efforts & reply. I couldn't find the code in Haynes either.

    Here we are over a year later still the same code, yes 18, still clearing it by battery dis-connect, everything still running great. It ran for about 8 months without generating the code, and started again just intermittently, then more regularly, and back to only every so often.

    Finally found the 18 code listed on chevroletforum.com, "18 crank or cam sensor error".

    Wishin' I had my old '56 back!

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