2007gmc sierra classic hd

[RandyD]

GMC pickup won't start! I just put another engine in it its been down for about a year and a half. When the key is off, there I be got 12v at starter . when I turn key on it doesn't . the instrument panel has the security light on along with everything else. The only way to get power to go off is disconnect the battery. Anyone have any clues?

[carriedi]

you should have 12 vo0lts on the big cable at the starter all the time. It should be the direct cable to the battery. The small wire to the starter (the starter solenoid wire from the key, the purple wire) should have 12 volts only in the start position on the ignition switch. That is the wire that sends the signal to the starter to spin the engine. If the big cable to the starter has 12 volts at the starter but loses it when you turn the key on, check you ground. Make sure the body and the block have ground wires that connect to the negative terminal on the battery.

if you just changed the engine make sure you don't have any wires crossed or any pinched wires.

The security light may be on because the passlock may have lost the code. try to start the engine once and if it doesn't start and the security light stays on leave the key in the on position for 10 minutes. You may need to leave the battery charger on so it doesn't kill the battery. That should reprogram the passlock. If the security light goes out after the 10 minutes is up it should have relearned the key and start up.