Key Takeaways: Why It's Not Starting
- Weak Battery: The #1 cause. Cold weather drops voltage, and remote starters have a safety cutoff if voltage is too low.
- Frozen Sensors: Hood latch switches and door sensors often freeze or get stuck, fooling the car into thinking something is open.
- Key Fob Battery: Cold temps zap the small battery in your remote, reducing its range significantly.
- Check Engine Light: If your car has thrown a code (even a minor one), most factory remote starts disable themselves for safety.
- Low Fuel: Many modern cars (like Fords and Toyotas) wont remote start if the fuel light is on.
The Short Answer
If your remote start isn't working now that the temperature has dropped, it is almost certainly your car battery or a frozen hood latch.
Here is the deal: Remote start systems are incredibly sensitive to voltage. When you try to crank a frozen engine, it takes a massive amount of power. If the system detects that the battery voltage is dipping too low (usually below 11.5 or 12 volts), it aborts the start immediately to save enough juice so you can eventually start it with the key. Even if your car starts fine manually, the remote start "brain" is much pickier.
Go out to the car, pop the hood, and make sure the hood switch isn't frozen stuck. If that looks okay, you need to test your battery.
Why Your Car Hates the Cold
I know how frustrating this is. You bought the remote start specifically for these freezing mornings, and now its the only thing broken. Irony at its finest, right? But before you go calling a mechanic or ripping out wires, lets just talk about why this happens. It helps to understand the "why" so you can fix it yourself.
Cold weather changes the chemistry in your car. According to battery manufacturers like Interstate Batteries, a car battery loses about 35% of its power at 32°F and up to 60% of its power at 0°F. Thats a huge drop. At the same time, your engine oil turns into molasses, making the engine harder to turn over. So you have less power available to do a much harder job.
The remote start system sees this struggle and shuts down to protect itself and the car.
Top 6 Reasons Your Remote Start Failed (And How to Fix Them)
1. The Battery Voltage Drop
This is the big one. I really cant stress this enough. Most people think, "Well, my car starts fine when I turn the key, so the battery is fine."
Not exactly.
When you use a physical key (or push-to-start button inside the car), you are bypassing some of the software safety checks that the remote starter uses. The remote starter is programmed to be cautious. It monitors the voltage while it tries to crank. If that voltage drops below a specific threshold (let's say 10 volts) for even a fraction of a second, the computer says "Abort!" and kills the engine.
The Fix: Go to an auto parts shop; most of them will test your battery for free. If it's more than 3 or 4 years old, just replace it. A fresh battery usually solves 90% of cold weather remote start issues.
2. The "Hood Ajar" Safety Switch
This is a safety feature that exists on every remote start system, whether it came from the factory or you bought a Viper or Compustar aftermarket one. The idea is simple: you don't want the engine to remotely start if a mechanic has their hands inside the engine bay. That would be a disaster.
So, there is a pin or a tilt switch under your hood. When the hood is closed, the pin is pressed down. When the hood opens, the pin pops up and disables the system.
In the winter, grease and dirt around that pin get thick and sticky. Sometimes water gets in there and freezes solid. So, even though your hood is closed, the pin is stuck in the "open" position (or the sensor inside the latch is frozen). The car thinks the hood is open, so it refuses to start.
The Fix: Locate the hood pin (usually near the headlights or built into the latch). Wiggle it. If its stuck, spray some silicone lubricant or WD-40 on it to displace the water and get it moving again. Clean off the gunk.
3. The Check Engine Light (CEL)
Did you notice a little orange engine light on your dashboard yesterday? Even if it was just for a second?
Modern cars are smart. If the computer detects a problem-anything from a loose gas cap to a misfiring cylinder-it triggers the "Check Engine" light. When this light is on, the car enters a sort of safety mode. Most manufacturers (GM, Ford, Toyota, etc.) program the car to disable remote start when the CEL is on. They do this because they don't want the engine running without a driver present to hear or smell if something is going wrong.
Cold weather often triggers false codes, like sensor errors or emissions issues, because parts shrink and seals get hard in the cold.
The Fix: You need to clear the code. Check your gas cap first (tighten it until it clicks). If the light stays on, get an OBD2 scanner (they are cheap on Amazon) to read and clear the code. Once the light is off, your remote start should work again.
4. The Key Fob Battery is Frozen
Sometimes the problem isn't the car, it's the thing in your hand. Batteries rely on chemical reactions to create electricity. Cold slows down these reactions. If your key fob battery was already weak, the walk from your house to the driveway in freezing temps might drop the voltage enough that it cant send a strong signal.
If you are trying to start the car from inside your house and it's not working, try holding the remote up to your chin (weird trick, but your skull acts as an antenna amplifier-seriously, look it up) or just get closer to the window.
The Fix: Replace the CR2032 (or whatever size) battery in your fob. It costs like five bucks.
5. Low Fuel and Oil Pressure
My friend has a Toyota RAV4 that drove him crazy last winter. Every time it got super cold, the remote start quit. Turns out, he was running his gas tank near empty.
Many cars have a "Low Fuel" logic built into the remote start. If the fuel light is on, the system disables remote start so you don't idle the car for 10 minutes and run it completely dry before you even get in. Since cold weather can sometimes make fuel gauge sensors fluctuate, this might be your issue.
Also, thick oil causes high oil pressure on startup. Some aftermarket systems monitor oil pressure. If it spikes too high (because the oil is like sludge), the system might cut the engine.
The Fix: Keep your tank at least half full in the winter. It helps with traction anyway!
6. "Tach Sensing" Issues (Aftermarket Systems)
If you have an aftermarket starter (like a Viper or Python), it uses a "Tachometer Signal" to know if the car has actually started. It listens to the engine revs.
In the cold, engines crank slower and idle differently. Sometimes, the remote starter doesn't "hear" the engine start because the RPMs are different than when you programmed it in the summer. It might try to crank, think it failed, and give up.
The Fix: You might need to re-learn the tachometer signal. Usually, this involves starting the car with the key, holding a button on the remote start antenna/brain until it flashes. Check your manual for "Tach Learning Procedure."
Valet Mode: The Silent Killer
I have to mention this because I've done it myself. Most remote start systems have a "Valet Mode." This is a mode you put the system in when you hand your keys to a parking valet or mechanic so they don't accidentally remote start the car while working on it.
When Valet Mode is on, the keyless entry (lock/unlock) still works, but the remote start is dead.
Sometimes, if your battery dies or if you fumble the buttons on your remote with gloves on, you can accidentally trigger Valet Mode. Usually, the parking lights will not flash when you lock the doors if this mode is active, or the LED light on the antenna (on your windshield) will stay solid blue or red instead of blinking.
To fix it: Look at your antenna. If the light is solid, you are in Valet Mode. The process to turn it off varies, but usually, it involves turning the ignition on and tapping the "valet button" (a little black button under your dash) or holding two buttons on your remote simultaneously. Google your specific remote model + "exit valet mode".
How to Troubleshoot (Step-by-Step)
Okay, lets break this down into a logical order so you don't waste time.
- The "Flash" Test: When you press the remote start button, does the car react at all? Do the parking lights flash?
- If NO reaction: Check your key fob battery. If that's good, check if you are in Valet Mode.
- If lights flash but no crank: It’s likely a safety sensor (Hood pin, Brake pedal switch, or Neutral safety switch).
- If it cranks but won't start: This is likely a Tach sensing issue or an immobilizer bypass issue (the car doesn't recognize the "digital" key).
- If it starts then immediately dies: This is usually the system not detecting the engine is running (Tach issue) or voltage drop.
- Check the Dashboard: Start the car manually. Is the Check Engine Light on? Is the "Hood Open" warning on the dash? Is the Low Fuel light on? Fix those first.
- Listen: Stand next to the car and hit the button. Do you hear clicking? Rapid clicking usually means the battery is too weak to turn the starter motor.
Preventing This Next Winter
Once you get it fixed, you don't want to deal with this again next year. Here is what I recommend to keep your remote start happy:
Get a Battery Maintainer (Trickle Charger). If you don't drive a lot, your battery never gets fully charged. A weak battery freezes faster (fun fact: a fully charged battery won't freeze until -76°F, but a dead battery can freeze at 32°F). Plug it in overnight when it's super cold.
Switch to Synthetic Oil. Synthetic oil flows much better in cold weather. This makes it easier for the engine to spin, which puts less strain on the battery, which keeps the voltage higher, which keeps the remote start happy. It’s a win-win.
Clean Your Latches. Every fall, wipe down your hood latch and door latches and spray them with white lithium grease. This keeps moisture out so they don't freeze.
Frequently Asked Questions
Does cold weather drain the remote start battery?
Technically, yes. Cold weather drains all batteries. The coin-cell battery in your fob will lose voltage in the cold, which reduces the range. Keep your keys inside a warm pocket rather than in an outside coat pocket if you're having trouble.
Can I reset my remote starter?
Yes, but it depends on the brand. For many factory systems, disconnecting the main car battery for 15 minutes acts as a hard reset (warning: you will lose your radio presets). For aftermarket systems like Viper, there is usually a toggle switch on the control module under the dashboard that you can flip off and on.
Why do my lights flash 7 times?
Remote start systems communicate via parking light flashes. If you try to start it and it fails, count the flashes.
Examples (vary by brand):
- 2 Flashes: Hood pin is open.
- 3 Flashes: Brake pedal is pressed.
- 7 Flashes: Manual transmission mode error or Timer mode.
Check your user manual for the "Diagnostic Codes" table.
Will remote start damage my engine in the cold?
Actually, it's safer than just hopping in and driving. Remote starting allows the oil to circulate and warm up slightly before you put a "load" on the engine by driving. However, don't let it idle for 30 minutes. 5 to 10 minutes is plenty to get the fluids moving.
Why does my car start then shut off after 5 seconds?
This is almost always a "Tach Lock" failure. The remote start thinks the engine didn't catch, so it cuts power to try again or gives up. It could also be the factory immobilizer (anti-theft) not accepting the signal from the remote start bypass module.
Hopefully, this helps you get warm! If you’ve checked the battery and the hood pin and it still wont work, it might be time to take it to a 12-volt specialist shop (like Best Buy or a local audio shop). But try the lube and the battery test first-it usually saves the day.