Trouble code (MIL) reset

You clear the codes with a code reader or scan tool. If the light came back on in two days with the same code the same problem came back.

THERE IS A CHIP IN THE KEY I BELIEVE. THERE IS A RELEARN PROCEDURE YOU CAN TRY IF WHEN YOU TRY AND START IT THE SECURITY LIGHT FLASHES. HOOK UP A BATTERY CHARGER. TURN THE KEY ON AND TRY AND START THE CAR AND RELEASE . DO NOT TURN KEY OFF LEAVE IT IN THE RUN POSITION. AFTER 10 MINS THE LIGHT WILL STOP FLASHING. TURN KEY OFF. TRY AND RESTART CAR AND AGAIN DO NOT TURN KEY OFF LEAVE IN THE RUN POSITION. LET SET 10 MINS AGAIN. LIGHT WILL STOP FLASHING AFTER THAT 10 MINS. DO IT AGAIN FOR THE 3RD TIME. SHUT KEY OFF LET SET 5 SECONDS AND START THE VEHICLE. HOPE THIS HELPS

put the fuse back in and try this,, when the alarm goes off, try holding down the Lock and unlock buttons at the same time, that should reset your alarm

The warning light comes on for a variety of reasons, anything from an ignition problem to vacuum leak. You can take it to your local dealership or auto parts store and they can usually hook up a reader to the computer in your car and read the trouble code which well tell you exactly why the light came on.
If you would like to read the code yourself here is what you do: To check the fault code yourself from the comfort of your own garage, put the ECM in "Diagnostic Test Mode II" by doing the following:

1) Sit your **** in the driver's seat.
2) Turn the ignition key to the ON position and wait three seconds. (Do not start the car.)
3) Fully depress and release the accelerator pedal five times in less than five seconds. (If you've got bad ankles, give up now and drive the car to the dealer.)
4) Wait exactly seven seconds. Fully depress the accelerator pedal and hold it down for about ten seconds until the MIL light begins flashing.
5) Release the accelerator pedal and start counting flashes to obtain the four-digit trouble code. Long flashes (0.6 seconds) indicate the first digit of the code; count the blinks one through nine and write down the first digit. (Ten blinks indicates a zero.) The next three digits follow in turn in the same fashion except with faster blinks (0.3 second) and a 1.0-second pause between digits.

The ECM code repeats intself until you turn the ignition key to the OFF position, at which point the ECM resets itself to standard get-in-and-drive-the-car mode. You can look up the trouble codes in the ESM/FSM; there's a bunch of them. In the ESM, refer to page EC-639. Additionally, if you get four blinks of ten (0000), the ECM is indicating no malfunction.

You can clear the code (and the annoying MIL) by holding down the accelerator pedal for more than 10 seconds while in Diagnostic Test Mode II. When you release the pedal, the ECM erases the trouble code(s).

Leave the key in the run position until the security light stops blinking. This should take 10 minutes. Then turn the key off, wait 5 seconds and try to start it. The security light should be blinking again. Leave the key on again for 10 minutes. Repeat this 3 times. After the third time on the the next start it should start and run fine. This will reprogram your theft system.

You need to reset the Passlock security system to your Tahoe.

1. Attempt to start the car, let it stall, but DO NOT turn the key off! Leave it in RUN.
2. Wait 10 minutes or until the Theft System light glows steady instead of blinking.
3. Do not turn the key off, but start it immediately.
4. This should reset your Passlock system.

Good luck and thank you for using Fixya.

If that does not work then your may have to do the 30 min relearn. You do basically the 10 min thing with the security light trick instructions above. Here goes this only works if your secuity light is on.

Put key in ignition don't start the car but you want to turn the key all the way on and release it back to the on position wait 10 mins or till the security light stops flashing repeat this the exact same way two more times( dont take key out) ending in about 30 mins total time. this should reset the code to the computer and you should have no more problems with it.

im just gonna take a stab in the dark here i understand that your security light is on try unlocking your door with your key sometimes you just need to reset the security. otherwise ive seen a security module go bad that may be preventing you from starting it.

You could try resetting the computer. The car maybe in lockout mode. Try turning your car over….leave the ignition on. Wait exactly 10 min. Then try turning over again….again leave the key on. Wait exactly 10 min and do it a third time….this time the car should start…maybe run a lil rough while it relearns the processes of your vehicle again. It is important to wait the exact 10 min each time. You will probably need a battery charger or a set of jumper cables because if your car goes low during this process it will not work. Good luck and I hope this works.

It sounds like you need to replace your computor. You could try resetting the computer first. The car maybe in lockout mode. Try turning your car over….leave the ignition on. Wait exactly 10 min. Then try turning over again….again leave the key on. Wait exactly 10 min and do it a third time….this time the car should start…maybe run a lil rough while it relearns the processes of your vehicle again. It is important to wait the exact 10 min each time. You will probably need a battery charger or a set of jumper cables because if your car goes low during this process it will not work. Good luck and I hope this works.

not that i am aware of but a theft system reset works quite well. i actually just had to do this today at work. turn your key to the on position and leave it there for 10 min. no less then 10 min. after that turn key off for 5 sec and turn back to on position. wait for light to go out and start complete reset is done