Security system disabled start

My yukon denali won't start from time to time. Normally if no start, I'll wait 10 mins or so and try again till it does. The security light inside will blink constantly and now will not turn over for a few days now. I am 99% sure it has to do with the security system (vats) and only have 1 key. When it does start, it starts like new. This time I'm out of luck and time. I'm a disabled combat veteran and dont have the funds to bring it in anywhere. I'm looking to fix this asap because this is my only vehicle. Any help would be appreciated especially a detailed way to pass loc
Experienced mechanics share their insights in answering this question :
If the starting problem was there all the time, then it would most likely be the body control module. But since this is an intermittent problem, then you may have connections issues to the body control module or ignition vats module. I would recommend disconnecting the battery and disconnecting at the modules and adding dielectric lube to the pins. After, reinstall the connections and reconnect the battery. If this cures the problem, then you had a connection that was causing too much resistance and a voltage drop in the system. If the problem continues, then the body control module may be causing the problem. The connection issues are more common. If you are looking to have this checked, a technician from YourMechanic can come to your car’s location to diagnose your car’s starting issue and perform any needed repairs.

How to Identify and Fix Common car Problems ?

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There are some cars that will recognize the key from you simply turning it back and forth in the door`s cylinder. It is best to try both methods: holding the key in the door, as well as turning the key both ways to disable the anti-theft system.
If your security light is on and you can`t turn the car on: Start by trying another key if you have one. In most cases, the security light means that the car no longer recognizes the key you`re using, so you may be able to reset the system by using a different key. to your dealership to program a new key for your car.
If your ECU controls the anti-theft system, disconnecting the battery may lock you out of your car. Like desktop computers and most other electronics, disconnecting the battery cable for a short period will not fully reset your ECU due to the residual power remaining in the circuits.
However, there are a few things you may do if you`re wondering how to stop the anti-theft mechanism without a key. One common method is to press and hold the “unlock” button on the car door for around 10 seconds; this should turn off the security system.
You can reset your alarm system by powering it down and then powering it back on. This is what is known as a power reset. To power down the system, the backup battery must be disconnected, and the transformer must be unplugged. Then reconnect the battery and transformer to power it back on.
Placing the key inside the keyhole

You can bypass the immobilizer by placing the key in the keyhole hence deactivating the car`s immobilizer to remote start.

Put the key in the ignition and rotate forward two clicks to the “On” position that makes the dashboard light up, but don`t try starting the car. Leave the key there for 15 minutes; it doesn`t always take that long, but it can. After that time, check to see if the anti-theft light has gone out, if one was lit up.
Advanced Theft Deterrent, if equipped, is designed to help deter the theft of your vehicle, gas and wheels. It also helps protect against break-ins through broken windows that would otherwise not be detected.
Dial 1-800-537-5140 to connect with GM`s toll-free radio hotline. Once you`re connected, you`ll be asked to provide your vehicle`s radio identification number, along with a special dealer access code. You`ll then be rewarded with a 4-digit retrieval code, which will allow you to unlock your radio.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

Fuel pump engages. Batery good, alternator good volts, jump start helps when wont start. Temp does not matter. Intermittent?
ANSWER : Hello. Thank you for writing in. There are several reasons your vehicle may only start when jump starting. The first and most common is a build up of resistance that is causing you to need a boost of voltage to get the engine started. This may be due to poor battery cables, a bad ground connection, a poor starter solenoid, and a couple of other issues. The first thing you want to do is perform a visual inspection of the starting system. Make sure there is no corrosion build up in the battery cables. You can also check the resistance across these wires and make sure you have a solid connection between components. You then want to make sure the starter solenoid is doing its job. It is responsible for taking the small amount of electricity sent by the ignition and turning it into a huge electrical charge that is strong enough to push over the engine with the help of some gear ratios in its favor. Do some more testing, and stick to the basics before assuming its something seriously complicated.

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Security system disabled start
ANSWER : If the starting problem was there all the time, then it would most likely be the body control module. But since this is an intermittent problem, then you may have connections issues to the body control module or ignition vats module. I would recommend disconnecting the battery and disconnecting at the modules and adding dielectric lube to the pins. After, reinstall the connections and reconnect the battery. If this cures the problem, then you had a connection that was causing too much resistance and a voltage drop in the system. If the problem continues, then the body control module may be causing the problem. The connection issues are more common. If you are looking to have this checked, a technician from YourMechanic can come to your car’s location to diagnose your car’s starting issue and perform any needed repairs.

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Vehicle won’t start, once it’s jump started it only stays running until you turn it off, then it work start again without jumping.
ANSWER : Hi there. There could be two problems here. It is possible that your battery is bad and will not take a charge from your alternator while driving. In that case every time you shut your car off you will not have enough juice to start it again. Inspect your battery – it should have at least 12.5 to 13 volts to start your car, if it doesn’t you will need to replace the battery. The second problem could be that your alternator is bad and not charging your battery, in this case you will need to replace your alternator. Both the battery and the alternator can be tested in your car. If you would like to have the car checked for you, a certified professional from YourMechanic can come to your car’s location to diagnose the starting problem and proceed with repairs.

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Cranks over start than dies
ANSWER : Hi There,
The idle air control valve is a small valve on the engine’s intake system that reads the air intake as it comes into the motor. This is controlled by the car’s ECM which uses this information to make adjustments to the air/fuel ratio depending on various inputs such as outside air temperature, intake air temperature, load and various other things. As you accelerate, your car’s engine is receiving a much higher dose of fuel than when at idle and conversely, when you let off the gas pedal, there is a sudden change in this fuel supply as a result of your foot letting off the pedal. When this happens, the job of the idle air control valve is to bring this deceleration down to a slow and smooth idle rather than suddenly cutting off the fuel supply causing the motor to die. When the idle air control valve is not working properly, this cause a disruption in this process resulting in the engine not being able to idle properly. I would recommend having a professional come to your location to diagnose and inspect your vehicle.

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Disable or bypass factory security system
ANSWER : To temporarily override the system, see these instructions. A permanent bypass requires re-engineering the system because engine immobilizers these days rely on multiple electronic modules and chips, the very removal or modification of any one of which, or reconfiguration, will itself activate the immobilizer. These immobilizer systems are complex and nearly foolproof to all but highly trained electrical engineers and even they will have trouble due to the need for specialized components, programming and so forth. That’s why these systems have been so effective of late in preventing car thefts. Immobilizers are essentially undefeatable unless you want to spend many, many hours poring over circuit schematics to design a unique bypass strategy. The bottom line is, in your circumstances it will be vastly easier, more efficient, and less costly to simply fix the immobilizer system that you already have in place. Indeed, the Factory Service Manual has a diagnostic protocol to accomplish just that. To that end, if you request a system electrical diagnostic a certified Mechanic, dispatched by YourMechanic right to your location, will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.

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What do I do when the car won’t crank and shows ‘check starting system’? But after a couple of trials it starts without any issues
ANSWER : Hello. The first thing to understand is that the check starting system light illuminates for several reasons. The starting light will give you a diagnostic troubleshooting code when the vehicle is scanned with the light on. Due to the fact the car eventually started without any issues, its likely the actual starter and battery (main components) are working just fine. Your issue is probably a bad connection or a fuse. One of the fuses is located under the drivers fuse box under the dash. Check the diagram on the panel for the exact fuse number. Also make sure the connections are all secure. There are some electrical tests that you can perform, but you need to replicated the no start situation before we can do that. If you seek professional help, it will be the exact same situation, and this can lead to hours of diagnostic work and hefty bill. Unfortunately this means the you will want to wait until the vehicle wont start, and then test for available voltage at the starter.

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How do I deactivate an anti-theft system?
ANSWER : This model uses the GM Pass Key security system, which includes an "electronic" key with a raised contact and a lock tumbler with a sensor that detects the electronic key. Either the key or the sensor in the tumbler has failed. Either failure will cause the "no start" condition you notice.

If you have multiple keys and neither key works, it is the sensor in the tumbler that has failed. If only one key fails, then that specific key should be replaced. I would recommend having an inspection into why the car will not turn over completed by a mobile, professional mechanic, such as one from YourMechanic, to diagnose this problem and get an accurate assessment of the needed repairs.

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My Blazer will crank over but not start by itself. It needs starting fluid to start.
ANSWER : Hi there. If you have not replaced your EGR valve, mass air flow sensor or the TPS on your Blazer, you might want to start with these repairs. It is also possible that the throttle body itself is damaged, especially if you’re able to start it on fluid. If you want to avoid chasing parts and repairs, the best solution may be to have a professional mobile mechanic come to your location and complete a car is hard to start inspection.

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