The Chrysler 300M “Key Fob Not Detected” message is a common issue on later models. The good news is that Chrysler’s key fob technology is usually pretty reliable, and you can still start your car with a dead key fob (that section is right here if you’re stranded while reading this).
The number one fix for a key fob that is not detected is to replace the battery.
Key fobs are small, wireless remote controls. They are used to lock and unlock your 300M’s doors, activate its alarm system, and even start the engine.
The most common type of key fob is a transponder key; it contains an embedded microchip that sends a unique signal to the car’s computer when the key is inserted into the ignition. This signal unlocks your car, allowing it to start.
How to Start a Chrysler 300M With a Dead Key Fob Battery
The odds are that if you’re reading this article, your Chrysler 300M has a “Key Fob Not Detected” warning, and you’re trying to get it to start. You can still start your car’s engine, and you don’t have to replace the batteries in the key fob to do so.
Step 1: Gain Access to the Vehicle
The first step to starting your 300M is getting into it. The key fob has a physical key that you can use. Slide the button on the back of the fob to gain access to the key.
Next, walk over to the driver’s side door. You should see an old-fashioned keyway. Put the key in and turn it counterclockwise. The door should unlock. Now, if the alarm goes off, don’t worry; the next step should turn it off.
Step 2: Turn the Ignition On
You should still be able to get your 300M to start by placing the key fob as close to the button as you can while pushing it.
Use the keyfob itself to push the start button. Even with a dead battery, the antennae in the ignition module should still pick up the transponder. If you would like a demonstration, watch the video above.
Key Fob Not Detected: Common Causes
A dead battery is the most common reason the Chrysler 300M doesn’t detect a key fob. Water damage is the next most prevalent reason. If you have access to the other key fob, you can use it to verify that your car can detect it.
Dead Key Fob Battery
Start with the key fob battery. If your 300M’s key fob battery is dead, it won’t be able to transmit a signal and will not work to power the door locks, and will only start the vehicle at extremely close range.
Water can cause significant and potentially damaging corrosion on key fob batteries and wiring. The Chrysler 300M’s key fob is designed to take a little water without a problem. It’s when they get soaked that they can get damaged.
If the key fob has been exposed to water, the battery will likely need to be replaced. If the circuit board is damaged, the whole fob may need replacing. You can try putting it in a dry rice bag to pull the moisture back out.
If you have both of your 300M’s key fobs, see if the other will start the car. If it does, the unresponsive key fob either has water damage, a wiring issue, or a dead battery. Since a dead battery is the most likely cause and the easiest to address, start there.
Out of Range
Most modern key fobs have an operating range of 30 to 50 feet, depending on your 300M’s model year. They must be within a few feet of the ignition button to work. If the key fob is too far away from your car, it won’t be able to communicate with it.
If you got the “Key Fob Not Detected” after you start the Chrysler 300M, it’s likely that the key fob was within range, and you drove away from it. Do not shut off the ignition until you return to where the key fob was, or the start button will stop working.