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    jdelong's Avatar
    jdelong Posts: 7, Reputation: 1
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    #1

    Feb 27, 2009, 05:10 PM
    How do I check a pcm to see if it works?
    I have a s10 that doesn't have any power at the diagnostic conector in the cab. I don't know where to start to check the pcm if it works or not. My check engine light stays on and the pickup fluds itself. It has Tbi. I chicked the wires from the pcm to the diagnostic conector and nothing is frayed cracked pinched or broken. I don't want to buy a new pcm for it if it doesn't need one. Any answers will help. Thanks
    TxGreaseMonkey's Avatar
    TxGreaseMonkey Posts: 16,761, Reputation: 5597
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    #2

    Feb 27, 2009, 05:42 PM

    With ignition switch ON, check for 5 reference volts on key sensors; e.g. MAP Sensor or TPS. You may need to isolate the "key sensor" on your truck. If voltage is a fraction of a volt, the odds are that the PCM is shot. It's very likely your PCM is bad, since the CEL stays on.
    this8384's Avatar
    this8384 Posts: 4,564, Reputation: 485
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    #3

    Feb 28, 2009, 07:47 AM

    What year is your S-10? Some vehicles lose power to that connector if a fuse is blown.
    jdelong's Avatar
    jdelong Posts: 7, Reputation: 1
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    #4

    Mar 1, 2009, 12:32 PM

    IT is a 1994 s-10. Ive checked the fuse panel in the dash and all fuses are good. I don't know if there are any fuses under the hood to check. All I see are about 4 or 5 fusible links that are sealed. Not sure how to check those either. The pcm has Red, blue, and gray wiring harnesses.
    jdelong's Avatar
    jdelong Posts: 7, Reputation: 1
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    #5

    Mar 13, 2009, 09:42 AM
    Quote Originally Posted by this8384 View Post
    What year is your S-10? Some vehicles lose power to that connector if a fuse is blown.
    It is a 1994. It's the newer body style although it requires a lot of parts from a 1993 because it was manufactured in nov. of 1993.
    TxGreaseMonkey's Avatar
    TxGreaseMonkey Posts: 16,761, Reputation: 5597
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    #6

    Mar 13, 2009, 09:56 AM

    On most vehicles the PCM fuse is in the underhood fuse/relay box. Check all underhood and underdash fuses with a test light or multimeter--not visually:

    https://www.askmehelpdesk.com/cars-t...tml#post252145

    Also, locate and clean the main PCM ground. Some Chevy trucks have a fuse panel on the side of the dash, as you open the driver's door, plus under the hood.

    Another possibility is that the ignition switch is bad. Check the contacts for wear, pitting, or melting.
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