Key Takeaways: Why Your Jeep Won't Start
- Check Engine Light: If your dashboard has a check engine light on, the remote start is automatically disabled by the computer.
- Low Fuel: If the fuel light is on, the Jeep wont start remotely to prevent running dry.
- Door/Hood Ajar: The most common mechanical issue is a faulty hood latch sensor or a door not fully closed.
- Battery Voltage: The 2021 Wrangler has a dual battery system. If the auxiliary battery is weak, remote start is often the first feature to get cut.
- Limit Reached: You can only remote start the vehicle twice in a row. After that, you must physically start it with the button inside.
The Quick Fix: What to Check First
Okay, let’s get right to it. If you're standing in your driveway freezing your butt off and your 2021 Jeep Wrangler is refusing to remote start, 90% of the time it is one of three things. Go check these right now:
- Look at the dash: Is there a Check Engine Light (CEL)? If yes, that's your problem. The system is designed to disable remote start so you don't damage the engine remotely.
- Check your gas gauge: Is the low fuel light on? The Jeep saves you from yourself by not letting you idle away your last gallon of gas.
- Check the doors and hood: Walk around the Jeep. Push on every door. Go to the front and make sure the hood is latched tight. The JL Wranglers (that's the body style for the 2021) are notorious for hood latch sensors getting a bit finicky.
If you checked those three and you're still stuck, don't worry. We're gonna dive deep into the other causes below. It's usually something simple.
Understanding the "Safety Logic"
Here is the thing about modern cars, especially the 2021 Wrangler. They are smart, sometimes too smart for their own good. According to the Jeep owner's manual, the remote start system isn't just a fancy convenience feature; it’s tied into the security and safety systems of the car.
The computer runs a rapid "pre-flight check" the second you double-tap that button on your fob. If any single parameter is off, it aborts the start to protect the vehicle or the people around it. It feels annoying, but it's actually trying to help.
The "Two Start" Rule
I’ve had friends panic thinking their starter motor died, when really they just hit the limit. Jeep has a hard-coded rule: You can only perform two consecutive remote starts.
Each remote start cycle runs the engine for 15 minutes. You can extend it once (for a total of 30 minutes). Once that timer runs out, or if you turn it off and on twice remotely, the system locks out. You actually have to unlock the door, get in, and push the physical "Start" button on the dash to reset the cycle. It prevents carbon monoxide buildup if someone accidentally starts the car in a garage.
The Battery Issue (The JL Curse)
If you own a 2021 Wrangler, you need to know about the battery situation. Unlike older cars, your Jeep probably has two batteries under the hood. There is the big main battery and a smaller, hidden "Auxiliary" battery used for the Auto Start/Stop system (ESS).
Here is where it gets tricky. These batteries run in parallel. If the small auxiliary battery starts to die or loses voltage, it drains the main battery. The Jeep's computer (the PCM) constantly monitors voltage.
Remote start requires a healthy spike of voltage to engage. If the computer senses the battery level is even marginally low, it disables "non-essential" high-draw functions. Guess what goes first? The remote start.
How to test this: Does your Auto Start/Stop feature (where the engine turns off at red lights) work? If the dashboard says "Start/Stop Unavailable: Battery Charging" and it stays that way for days, your battery is likely too weak to support remote start.
The Hood Latch Sensor: A Common Failure
On the 2021 models, this is a super common headache. There is a small electrical switch inside the hood latch assembly that tells the computer the hood is closed. If the car thinks the hood is open, it will absolutely not start remotely. This is to prevent the engine from starting while a mechanic has their hands inside the fan belt.
Because Jeeps are, well, Jeeps, we drive them through dirt, mud, and salt. That sensor gets dirty. Sometimes the connector just gets loose.
The Fix: Pop the hood and look at the latch mechanism. You might see a small wire harness connected to it. Make sure it's clicked in tight. You can also try cleaning the latch with some electrical contact cleaner. If you press lock on your fob and the horn doesn't beep, it often means the Jeep thinks a door or hood is open.
The Key Fob Itself
Sometimes the problem isn't the Jeep, it's the thing in your hand. The 2021 key fob is pretty robust, but the battery inside (usually a CR2450) lasts about 2-3 years depending on usage.
If you have to stand really close to the Jeep to make it unlock, or if you have to press the button super hard, swap the battery. Even if the battery has enough juice to unlock the doors, the remote start signal requires a sustained, strong transmission. A weak battery might send the first signal but fail on the confirmation signal.
Also, watch your fingers. You need to press the remote start button (the x2 circle) twice within five seconds. If you press it too slow, it ignores you. If you press it three times rapidly, it might send a "start" then immediate "cancel" signal.
Detailed Troubleshooting Checklist
If you've gone through the basics and still have nothing, let's look at the specific conditions required by the manufacturer. If any of these are true, the remote start aborts:
- Shift Lever: The vehicle must be in PARK. If the shifter sensor is slightly off and doesn't register Park, no start.
- Hazard Lights: Are your hazard flashers on? Remote start is disabled if hazards are flashing.
- Brake Pedal: Is something pressing the brake pedal? A heavy bag on the floorboard leaning against the pedal will prevent starting.
- Vehicle Speed: This sounds silly, but the computer must read 0 MPH. A faulty wheel speed sensor could theoretically confuse it.
- Panic Mode: If the alarm was recently triggered, you usually have to start the car manually to reset the security system.
The "Uconnect" Settings Glitch
The 2021 Wrangler uses the Uconnect system (usually the 7-inch or 8.4-inch screen). Sometimes, weirdly, the software just decides to turn the feature off. This can happen after an "over-the-air" software update or if the battery died recently.
You should check to make sure it's actually turned on:
- Go to your touchscreen.
- Tap Settings.
- Scroll to Doors & Locks.
- Look for Remote Start System.
- Make sure the box is checked or toggled to "ON".
While you are in there, check the "Remote Start Comfort Systems" settings too. This controls if your heated seats or steering wheel come on automatically. It won't fix the starting issue, but it's nice to have set up.
Check Engine Light (CEL) Codes
Let's circle back to the Check Engine Light because this is the #1 culprit. You might think, "My car runs fine, the light is just on because of an EVAP leak," but the remote start doesn't care.
Common codes that trip this up on the 2021 Wrangler:
- P0456 (Small EVAP Leak): Often just a loose gas cap. If your gas cap isn't clicked tight, this code throws, and remote start dies.
- P0128 (Thermostat): If the engine isn't warming up fast enough, the computer throws a code.
- Misfire codes: Even a minor misfire you can't feel will disable the system.
If you have a CEL, go to an auto parts store like AutoZone or O'Reillys. They will scan it for free. Once you clear the code (and fix the problem), remote start usually starts working again immediately.
Cold Weather Issues
Ironically, remote start fails most often when you need it most-in the freezing cold. This usually isn't because of the cold itself, but because cold weather drops battery voltage.
A battery that reads 12.6 volts in the summer might drop to 12.1 volts in sub-zero temps. That voltage drop is enough to trigger the "Battery Protection Mode" we talked about earlier. If it's super cold and it won't remote start, try putting a trickle charger on the battery overnight. I bet it works the next morning.
When to See the Dealer
I try to avoid the dealership as much as possible because of the cost, but sometimes you gotta go. If you have checked the hood latch, changed the fob battery, ensured there are no check engine lights, and verify the main battery is strong, you might have a software corruption or a hardware module failure.
The 2021 models are heavily reliant on the RF Hub (Radio Frequency Hub). This is the brain that receives the signal from your key. There have been instances where this module locks up. The dealer can "flash" (update) the software or replace the hub.
Also, verify if your Jeep is actually equipped with remote start. I know, this sounds dumb. But I've had people buy a used 2021 thinking it had remote start because the key fob had the button, only to find out the previous owner replaced the fob with a generic one, and the car never actually had the module installed.
How to Reset the System (The "Battery Nap")
Before you spend money, try a "hard reset." Computers get glitches. Your Jeep is basically a computer on wheels.
1. Open the hood.
2. Disconnect the Negative (-) black cable from the main battery.
3. If you can access it, disconnect the negative on the Aux battery (though usually disconnecting the main interrupts the loop on the JL).
4. Wait about 15 to 30 minutes.
5. Reconnect the cable and tighten it well.
6. Go inside the car, start it manually, turn the wheel lock-to-lock (all the way left, all the way right) to reset the steering angle sensor.
7. Turn it off, lock the door, and try the remote start.
This clears out temporary memory buffers and can fix weird glitches with the hood sensor logic or the Uconnect system.
Final Thoughts
It's frustrating when technology fails, especially on a 2021 vehicle that isn't even that old. But generally, the Wrangler safeguards are there to keep the engine from blowing up or the car from getting stolen.
Most of the time, it's that pesky Check Engine Light or a loose Gas Cap. Start there, save yourself the diagnostic fee, and you'll probably be back to a warm car in no time.
Frequently Asked Questions
Why does my Jeep honk but not start?
If the Jeep honks once but the engine doesn't crank, it received the signal but the computer rejected the request. This usually points to a safety fault: a door is ajar, the hood is open, the hazard lights are on, or the Check Engine Light is on.
Can I add remote start to my 2021 Wrangler if I don't have it?
Yes, you can. You can buy the genuine Mopar kit. It usually requires installing a new hood latch with the safety switch and getting the dealer to flash the sales code (XBM) to the vehicle's computer so the car knows it has the feature.
Does the remote start turn on the heated seats?
It should, but only if you have "Auto-On Comfort" enabled in the Uconnect settings. It also depends on the outside temperature. Usually, it needs to be below 40°F (4°C) for the heated seats and steering wheel to activate automatically.
Does the 4xe (Hybrid) work differently?
Yes, slightly. The Wrangler 4xe might not start the gas engine if the battery has enough charge to heat the cabin electrically. Or, it might start the gas engine specifically to condition the battery. It also requires the charging cable to be unplugged in some software versions, though newer updates allow climate pre-conditioning while plugged in.
How far away does the remote work?
The factory remote start on a 2021 Wrangler is good for about 300 feet (91 meters) in open space. Buildings, other cars, and radio interference can cut that distance down significantly. If you hold the remote to your chin (sounds crazy, but it uses your head as an antenna), you can sometimes extend the range.