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your car won't start after you swapped
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the PCM you're turning the key but all
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you get is that security light blinking
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at you yeah that's the General Motors
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anti- theft system doing its job it
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thinks you're trying to steal your own
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car frustrating I know but don't worry
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you don't need a tow or a trip to the
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dealer just yet you can reprogram that
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key yourself and get your Chevy or GM
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vehicle back on the road
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i'm Tom from Car Justify and I've helped
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tons of drivers with this exact issue if
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you've just installed a new or used
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powertrain control module that's what
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PCM stands for and now the car won't
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recognize your key it's because the
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vehicle security system needs to learn
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the new module i'll walk you through
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what to do step by step in plain English
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required all right so here's the deal
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most late9s to mid2000s GM vehicles use
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a system called pass lock or pasi when
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you replace the PCM the anti- theft
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system thinks it's been tampered with
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and basically shuts things down the fix
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is what's called a key relearn and the
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good news you don't need a scan tool or
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any special equipment just some
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patience here's the basic 30inut relearn
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process first insert your key and turn
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it to the on position not start just on
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that's when all the lights on the dash
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come on you're going to leave it like
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that for 10 minutes don't touch anything
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just wait after 10 minutes the security
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light should turn off once it does turn
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the key off for about 5 seconds then do
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it again back to on for another 10
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minutes you're going to repeat this
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three times for a total of 30 minutes on
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the last cycle after that third
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10-minute wait and the light goes out
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turn the key off one last time wait a
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few seconds then try starting the car if
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everything went right it should fire
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up now if that doesn't work don't panic
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sometimes the battery voltage is low and
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the anti- theft system won't relearn if
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the battery is weak so make sure your
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battery is fully charged or hook up a
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charger while you're doing the process
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also check your grounds and fuses i've
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seen a loose ground wire or a blown fuse
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for the body control module that's the
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BCM mess up the whole
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relearn if you're using a used PCM keep
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in mind that in some vehicles especially
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newer ones the VIN number in the PCM has
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to match the body control module in that
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case a relearn might not be enough you
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might need a locksmith or a shop with a
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Tech2 scanner to do a VIN reprogram but
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that's usually only for later models for
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most mid200s or older GM cars and trucks
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the 30inut method works like a
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charm quick recap if your Chevy or GM
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won't start after a PCM swap and the
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security lights on try the 30inut key
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relearn make sure your battery is solid
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check your grounds and don't rush the
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process if it still won't start after
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that then yeah it might be time to get a
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done hope that helped if it did give the
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video a like and hit subscribe so you
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don't miss the next one i'm Tom from Car
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Justify see you in the next fix
