Check the battery in your key fob first
A dead or dying battery in your remote start key fob is the most common reason the system stops working. The fob sends a radio signal to your car's receiver, and a weak battery weakens that signal until the car no longer picks it up. You'll often notice the fob's other buttons (lock, unlock, trunk) work fine while remote start fails, because remote start requires a stronger signal than those functions.
Open the fob by prying gently at the seam with a coin or flat tool. Most fobs use a CR2032 or CR2025 battery — check the number stamped on the old battery and buy the exact same type at any drugstore or supermarket. Replace it, snap the fob back together, and test remote start from your driveway. If it works, you're done. If not, move to the next step.
Key Takeaways
- A dead key fob battery is the first thing to check, and you can replace it yourself in under a minute for about two dollars.
- Remote start may be disabled by a low fuel level, an open door or hood, or a manual transmission — check your owner's manual for your car's specific lockouts.
- If your fob battery is good and the car still won't start remotely, the receiver module in your car may have failed and will need a mechanic's diagnosis.
- Some cars require you to turn the key to the "On" position and back to "Off" three times in a row to arm remote start before the fob will work.
- A dead car battery will prevent remote start from working, even if the fob is fine — the car needs enough power to receive the signal and crank the engine.
Verify the car's battery has enough charge
Remote start requires your car's battery to have enough voltage to receive the signal from your fob and turn the starter motor. If the battery is very low or dead, the car won't respond to the remote command even though the fob is working fine. You may notice the dashboard lights are dim or the interior lights don't come on when you open the door.
Try unlocking the car with the fob's lock button. If that works, the battery has enough charge. If the doors won't unlock remotely either, the battery is too low. Charge or replace the car battery before troubleshooting further — a jump start from another vehicle will give you enough power to test remote start again.
Check for safety lockouts that prevent remote starting
Most cars disable remote start if certain conditions aren't met. These lockouts exist to prevent the engine from starting when it's unsafe. The most common ones are an open door, open hood, low fuel level, or a manual transmission in gear. Some cars also won't remote start if the engine is already running or if the interior temperature is too high or too low.
Close all doors and the hood, then check your fuel gauge — if it's below a quarter tank, fill up and try again. If you have a manual transmission, make sure the car is in neutral and the parking brake is set. Check your owner's manual for the complete list of lockouts for your specific model, because they vary widely between manufacturers. Once you've cleared all the conditions, test the fob again from outside the car.
Re-arm the remote start system if it's been disabled
Some car models require you to manually arm remote start before the fob will work. This is a security feature that prevents someone from starting your car remotely without your knowledge. The process usually involves turning the key in the ignition to a specific position multiple times in quick succession.
The most common method is to turn the key to "On," then back to "Off," then to "On" again, then back to "Off" — all within about 10 seconds. Some cars use a different sequence or require you to press a button on the fob while the key is in a certain position. Check your owner's manual for the exact steps for your vehicle. Once you've completed the sequence, the system should be armed and the fob should work. You may see a light flash on the dashboard to confirm the system is active.
Look for a blown fuse or tripped circuit breaker
The remote start receiver module in your car is protected by a fuse. If that fuse blows, the receiver stops working and your fob won't communicate with the car. A blown fuse usually happens after an electrical surge, a short circuit, or a failed component in the system.
Locate your car's fuse box — the owner's manual shows you where it is and which fuse controls remote start. Pull out the fuse and look at it against the light. If the wire inside is broken or blackened, the fuse is blown. Buy an identical replacement fuse at an auto parts store and install it. If the new fuse blows when ready, there's a short circuit in the system and you'll need a mechanic to diagnose it. If the new fuse holds and remote start works, the problem is solved.
Test the fob's range and signal strength
Remote start fobs work within a certain distance from your car — usually 50 to 100 feet depending on the model and any obstacles between you and the vehicle. If you're too far away, the signal won't reach the receiver. Try standing closer to the car, ideally within 30 feet with a clear line of sight, and press the remote start button.
If it works from close range but not from farther away, the fob's transmitter is weakening and may need replacement. If it doesn't work at any distance, the problem is the fob battery, the receiver module, or a safety lockout — go back and check those first. Metal buildings, dense trees, and other cars can block the signal, so test from an open area if possible.
When to take the car to a mechanic
If you've replaced the fob battery, verified the car battery is charged, cleared all safety lockouts, re-armed the system, checked the fuse, and tested the range, and remote start still doesn't work, the receiver module in your car has likely failed. This is an electronic component that receives the signal from your fob and tells the engine to start. Replacing it requires a mechanic with diagnostic equipment.
Before you go to the shop, write down exactly what you've already checked — this saves the mechanic time and may lower the diagnostic fee. Bring your key fob and owner's manual. The mechanic will use a scan tool to see if the receiver is communicating with the rest of the car's computer system. If it's not, they'll replace the module. If it is, they'll look for other causes like a failed starter relay or a broken wire in the system.
Frequently Asked Questions
Can I use a spare key fob to test if the problem is the fob or the car?
Yes, and this is a smart first test. If you have a spare fob, try remote start with it from the same distance and location. If the spare works, your original fob's battery or transmitter is the problem. If the spare doesn't work either, the problem is in the car's receiver or a safety lockout.
What if remote start worked before but stopped suddenly?
A sudden stop usually means the fob battery died, a fuse blew, or the receiver module failed. It's less likely to be a safety lockout unless something changed about how you're using the car — like a door that won't close all the way or a fuel level that's now too low. Start with the fob battery and work through the checklist in order.
Does cold weather affect remote start?
Yes. Very cold temperatures can weaken a fob battery's output and make the signal harder for the receiver to pick up. They can also prevent the engine from starting even if the signal gets through. If remote start fails only in winter, try a fresh fob battery first. If that doesn't help, the car may have a cold-weather lockout — check your manual.
Will remote start drain my car battery if I use it every day?
Remote starting the engine for a few minutes most days will use some battery power, but not enough to drain it if the alternator is working normally. The alternator recharges the battery while the engine runs. If you're remote starting the car and then not driving it, the battery may not fully recharge, so use it sparingly if the car sits unused for days.
Can I reprogram my key fob myself if the receiver isn't recognizing it?
Some cars allow you to reprogram a fob by turning the key in the ignition a certain number of times or pressing buttons in a specific sequence. The steps are in your owner's manual. However, if reprogramming doesn't work, the receiver module itself may have failed and will need a mechanic. Reprogramming is free to try and takes a few minutes.