Key Takeaways: How to Fix It Fast
- The Sequence: Press LOCK, press LOCK again, then HOLD LOCK for 3 seconds until the lights flash. Timing is everything.
- The Subscription Trap: On the 2021 Tundra, your key fob remote start might be tied to the Remote Connect subscription. If your trial expired, the key fob feature might stop working (yes, really).
- Physical Safety Checks: The truck wont start if the hood is unlatched, doors are open, windows are down, or the "Check Engine" light is on.
- Battery Health: A weak battery (even slightly low voltage) will disable remote start to save power for the actual crank.
The "Lock-Lock-Hold" Method (Try This First)
Look, I know you just want to get the truck running. If your 2021 Tundra remote start isn't working, 90% of the time it is simply because the button timing is off. It's not intuitive.
Here is exactly how to do it:
- Press the LOCK button on your fob. (Wait about 1 second).
- Press the LOCK button again. (Wait about 1 second).
- Press and HOLD the LOCK button for 3 full seconds.
Do not let go until you see the hazard lights on the truck flash. Once they flash, let go immediately. The engine should crank up about 3 to 5 seconds later.
If you press them too fast, the truck ignores it. If you press them too slow, it resets the count. It takes a little practice to get the rhythm right, almost like a slow heartbeat. Try that a few times before you go tearing the truck apart or calling the dealer.
The "Subscription" Problem (The Elephant in the Room)
Okay, we need to talk about the most annoying part of modern Toyotas. This is where a lot of people get confused and honestly, its a bit controversial.
For the 2021 Tundra (and many models after 2018), Toyota tied the functionality of the Key Fob Remote Start to the Remote Connect digital subscription. I know, it sounds crazy. Why would a radio signal from your key need a subscription?
According to various reports from The Drive and massive threads on Tundra forums, the Audio Plus and Premium Audio packages come with a trial of Remote Connect (usually 1 year or 3 years depending on the trim). When that trial expires, you don't just lose the ability to start the truck from your phone app-you often lose the ability to start it from the key fob too.
How to check if this is your problem:
Open your Toyota app or check your account online. See if your "Remote Connect" services have expired recently. If your remote start stopped working on the exact day your truck turned a year old (or three years old), this is definitely your issue.
You have two choices here:
- Pay the fee: You can subscribe to the service (usually around $8/month or $80/year) to get the functionality back.
- Go Aftermarket: Buy a third-party remote start kit. I'll talk more about this later, but honestly, it's often cheaper in the long run than paying a subscription forever.
Troubleshooting: Physical Safety Sensors
If you have an active subscription (or you are sure your truck doesn't require it) and the "Lock-Lock-Hold" method still isn't working, the truck's computer (ECU) is likely preventing the start for safety reasons. The Tundra is smart; it won't start if it thinks it might be dangerous.
1. The Hood Latch Sensor
This is the most common hardware culprit. There is a small sensor in the hood latch mechanism that tells the truck if the hood is closed. If this sensor is dirty, broken, or unplugged, the truck thinks the hood is open.
If the truck thinks the hood is open, it disables remote start so that the engine doesn't turn on while a mechanic has their hands inside the engine bay. That would be bad news.
The Fix: Pop your hood and look at the latch mechanism near the radiator. Look for a small electrical connector. Make sure it is plugged in tight. Sometimes grime or grease gets in there. You can try cleaning it with a little electrical contact cleaner. Also, try slamming the hood shut firmly to ensure it's fully seated.
2. Door and Window Check
It sounds silly, but double-check your doors. If a door is slightly ajar, the remote start sequence will fail. The truck will usually beep at you differently if a door is open when you try to lock it.
Also, verify your windows. While some systems allow windows to be cracked, if the alarm system detects an intrusion or if the sunroof is open in a weird way, it might prevent the system from arming correctly, which stops the start.
3. The "Check Engine" Light
This is a big one. Does your dashboard have any warning lights on? If you have a Check Engine Light (CEL), the remote start feature is automatically disabled. This is to protect the engine.
Even a minor issue, like a loose gas cap that triggers an emissions code, will kill your remote start. If you see that yellow engine light, you need to get an OBDII scanner (you can borrow one from an auto parts store for free) and clear the code or fix the problem before remote start will work again.
Battery Voltage Issues
The Tundra has a big V8 (well, the 2021 still does!). It takes a lot of juice to crank that beast over. The truck's computer monitors your battery voltage constantly.
If the battery is starting to get old and the voltage drops even a little bit below the "healthy" threshold, the truck goes into a preservation mode. It will still let you start the truck with the key or push-button inside because you are physically there, but it will disable "luxury" high-drain features like remote start to ensure there is enough power left to start the engine manually.
I had a friend whose remote start stopped working in the winter. He swore the battery was fine because the truck started okay when he got in. We tested it, and it was sitting at 12.1 volts instead of 12.6. He swapped the battery, and boom-remote start worked again.
Quick Test: If your headlights seem a little dimmer than usual or the truck cranks a little slower on cold mornings, swap the battery.
Other Weird Reasons It Might Fail
If you've checked the subscription, the button timing, and the safety sensors, here are a few oddball things that could be happening.
Valet Mode
Some security systems have a "Valet Mode" that disables the alarm and remote start so a valet driver doesn't accidentally set it off. Check your manual to see if you accidentally toggled this. Usually, the security light on the dash behaves differently if you are in this mode.
Spare Key in the Truck
The 2021 Tundra is smart enough to know if a key fob is inside the cabin. If you dropped your spare key under the seat, or if your spouse left their purse with the second key in the truck, the remote start often won't work. The truck thinks, "Why remote start? The key is right here, just push the button."
Search the cab for a lost fob.
Low Fuel
According to the manufacturer guidelines, many remote start systems will not engage if the fuel light is on. This is to prevent the truck from idling until it runs dry, which can damage the fuel pump (fuel pumps are cooled by the gas they sit in). If you are running on fumes, fill up the tank and try again.
The Aftermarket Alternative
If you figure out that your issue is the expired subscription and you refuse to pay Toyota a monthly fee just to use the hardware you already bought (I don't blame you), look into aftermarket kits.
There are plug-and-play kits available from companies like 12Volt.Solutions or Start-X. I have installed a Start-X kit on a Tundra before. It took about 20 minutes.
Why do this?
- No Subscription: You pay once for the hardware, and it works forever.
- Better Range: The factory fob range on the Tundra is kinda terrible. Aftermarket kits often use their own remotes with much better range, or they let you use the factory fob with the standard 3-click method without the subscription block.
- Easy Install: Most of these Tundra kits are "T-Harness" style. You basically pull off the plastic cover on the steering column, unplug a connector, plug the kit in the middle, and zip tie it up. No cutting wires.
Summary Checklist
Before you give up, run through this mental checklist one last time:
- Timing: Are you doing Lock, Lock, Hoooold (3 secs)?
- Subscription: Is your Remote Connect trial active?
- Doors/Hood: Is everything shut tight?
- Engine Health: Is the Check Engine Light off?
- Battery: Is the truck battery fully charged?
- Fuel: Do you have more than 1/4 tank of gas?
Usually, it's one of these simple things. Good luck getting it fired up!
Frequently Asked Questions
Does the 2021 Tundra SR5 have remote start?
It depends on the audio package. If your SR5 has the "Audio Plus" or "Premium Audio" package, it likely has the hardware for it. If you have the base audio system, you probably do not have factory remote start installed.
How long does the Tundra run on remote start?
By default, the Toyota system runs for 10 minutes. After 10 minutes, the engine will shut off automatically to save gas. You can usually do the remote start sequence again to add another 10 minutes, but generally, the limit is 20 minutes total before you have to physically enter the vehicle.
Why does the engine shut off when I open the door?
This is a Toyota safety feature, and yes, it is super annoying. Toyota designed it so that as soon as you unlock or open the door, the engine cuts out. You have to get in and restart it. They claim this is for anti-theft security so someone can't jump in and drive away, even though you technically need the fob to put it in gear. It's just a quirk of the brand.
Can I add remote start to my 2021 Tundra if it didn't come with it?
Yes, absolutely. Since the 2021 is a "push-to-start" vehicle (mostly), adding an aftermarket kit is very easy. As mentioned above, look for "T-Harness" kits that are plug-and-play. They are much cheaper than having the dealer install a factory unit.
Does the key fob battery affect remote start?
Yes. If your key fob battery (CR2032 usually) is weak, it might have enough power to lock the doors but not enough signal strength to send the sustained signal needed for the "Hold" part of the remote start sequence. Try changing the fob battery; it costs like $5.