Why My Car Starts On Its Own Without Key?

It can confuse the hell out of a car owner if the car starts on its own without key. The issue can be many. The wires for the battery terminal on the ignition switch could be swapped with the starting terminal on the ignition switch and can cause your starter to engage. Or it could be due to water entry in the car’s electrical system. The problem needs a proper diagnose.

In this article, we will learn about the common causes and their solutions. Here are the top 5 reasons that cause the problem. 

Why Does My Car Starts On Its Own Without Key? 

As the starting system is an electrical component, the reasons can be many. With the advent of a complex push-to-start system, the problem can be a module too. Let us understand them in the following points-

1. A Shorted Starter Motor Wiring

The most likely thing causing the car to start on its own is a short to power on the wire coming from the ignition switch, or going to the starter. This basically means that the starter motor relay is getting power and sending it to the starter. Or it could be that the starter is getting power from a short past the relay. Lastly, this could be a shorted or a bad relay as well.

How To Deal With Bad Starter Motor Electricals?

An easy way to figure out the problem is to check power at terminal 3 of the starter relay and at terminal 5 of the relay. If you have no power at terminal 3 then you have a short between the relay and starter on that wire. Replace the shorted wire or if there is a spliced wire, then get it repaired properly. You may also need to replace the starter relay too if it is welded shut. 

2. A Wonky Push Start Module

This feature uses a radio signal from a key fob to activate only when your key fob is on or within a few feet of you. The signal from your key fob will allow you to turn on your car with a push-button start. If the module dealing with the whole system has gone bad, then it can initiate an uncommanded engine start. It can be dangerous as your car can be easily stolen in this kind of situation.

Repair Options For Push Start Module

The start module is a major component of your car’s onboard computer, which regulates many systems and subsystems to start the car. The problem can be as simple as a bad solder joint or the whole unit could have been damaged due to water ingress or short circuit. If the repair is not possible, then you have to buy a new one. 

3. Sticky Car Remote Key

If you have a key fob or remote control with buttons that are functioning on their own, or they require you to press hard to get them to work, then it could be sticky buttons or damaged buttons on your remote key. The dirt or goo that has collected on the car remote key will cause an uncommanded start. This can also lead to a potential theft problem.

How to Fix A Bad Car Remote Key?

If you are using the repair kit, simply peel off one of the included aluminum foil dots and stick it on the bad or sticky button’s black contact point. Press it tightly against the contact point for 10-15 seconds to help adhesion. Clean the area with rubbing alcohol before installing. Use scissors, carefully cut out a piece of aluminum foil with double-sided tape attached that roughly matches the size and shape of the contact point.

4. Water Present In Car’s Fuse Box

Fuses are used to even out and reduce the electrical current that flows through wires to prevent damaging electronics from too much electricity. A rectangular fuse is composed of two push in-connectors linked by a fuse wire in a protective covering, typically made of plastic. If the water has entered the fuse box. Mostly the car starts on its own without key due to the havoc created by the water in the fuse box.

How To Deal With Electrical Issues?

Fuse boxes are made to protect electrical circuits in the car from exposure to the elements preventing damage and short circuits. If the water has entered the fuse box, you have to remove the whole unit and get it blown dry. See for the source of leaks and seal it shut to prevent the problem in the future. 

5. Cheap Car Accessories

There are sons of car accessories that are available in the market, which aids in remort start of the car. Most of the owners of the older generation vehicles opt for these accessories in order to match with the modern world. What they do not realize is that the use of cheaper car accessories can become a nightmare for them very quickly. Bad car accessories installed to remort start the car can cause it to start on its own.

Fix To Deal With Bad Car Accessories

The common solution will be to uninstall and throw the accessory into the garbage bin. There is no solution or fix for a cheap car component. You should avoid installing such stuff at all costs. In some cases, however, it can be due to faulty wiring. In that case, figure out the wiring by a good car electrician.

How Serious Is The Auto Start Issue Of The Car?

If your car starts on its own without key, then this can be a serious issue for your car. Your car can become a potential theft target for carjackers. Also, a car in a manual transmission can start to roll forward and can cause an accident. Lastly, the electricals can start a fire too. 

How Much Will It Cost To Fix Car Starter Issue?

For a typical car electrical issues, it can cost you around 200$. The labor can be expensive as it involves many man-hours to diagnose in some cases. If the push start module has gone bad, then be ready to shell a hefty price. The process can go upwards of 500$.


The issue of car starts on its own without key can be a serious one as it can be a theft potential and it can also cause damage to life and property, so it is better to get the issue resolved as soon as possible. If you still have any questions, ask them in the comments. 

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