FIXED: remote start not working and check engine light on

The Short Answer: Why Your Remote Start Is Dead

Here is the direct answer you are looking for: Your remote start isn't broken. The car's computer disabled it on purpose.

When your Check Engine Light (CEL) comes on, the vehicle enters a sort of "defensive mode." Manufacturers like Ford, Chevy, Toyota, and Honda program the car to shut off non-essential features when they detect an engine problem. Since remote start runs the engine without a driver sitting in the seat to watch the gauges (like oil pressure or temperature), the computer plays it safe and refuses to start the car remotely.

To get your remote start back, you have to fix whatever is causing the check engine light to turn on. Simple as that.

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The "Why": Thinking Like a Car Computer

It helps to understand why this happens so you aren't so frustrated at your car. Imagine if you woke up with a terrible fever and a stomach ache. You probably wouldn't want to go run a marathon, right? That is basically what your car is doing.

When you use remote start, usually on a freezing cold morning or a scorching hot afternoon, the car is idling high to warm up or cool down. If there is a problem with the engine-say, a misfire or low oil pressure-and you are inside the house drinking coffee, you wouldn't know the engine is destroying itself.

By disabling the remote start, the manufacturer forces you to get in the car and start it with the key or button. This ensures you are actually looking at the dashboard. If the engine starts smoking or the oil light flashes, you are there to shut it off immediately. It’s actually a pretty smart feature, even though it feels like a punishment when its 20 degrees outside.

Step 1: The "Gas Cap" Trick (Do This First!)

Before you go spending money at a mechanic, check the easiest thing first. I can't tell you how many times I've seen this happen.

If you recently got gas and didn't click the cap tight enough, the car's computer thinks there is a leak in the fuel system (it's called an EVAP leak). This triggers the Check Engine Light.

Here is what to do:

• Go to your car and unscrew the gas cap.
• Put it back on and tighten it until it clicks at least three times.
• Drive the car normally.

Note that the light won't turn off immediately. It usually takes a few "drive cycles" (driving for 15-20 minutes, parking, and cooling down) for the computer to realize the leak is gone. Give it a day or two. If the light goes off, your remote start should start working again automatically.

Step 2: Read the Code

If tightening the gas cap didn't work, you need to know exactly why the light is on. You don't need to be a mechanic to do this.

You have two options here, and both are pretty easy.

Option A: The Auto Parts Store

Most major auto parts stores (AutoZone, Advance Auto, O'Reillys, etc.) will read your check engine light for free. You just walk in and ask to borrow their OBDII scanner. They plug it into a port under your dashboard, and it spits out a code (like P0420 or P0300).

Write that code down. That is your golden ticket to fixing the remote start.

Option B: Buy a Cheap Scanner

Honestly, you should probably just own one of these. You can buy a basic Bluetooth OBDII scanner online for like $20. It connects to your phone and tells you exactly what's wrong. It saves alot of time and guessing.

Common Causes for the Light (and No Remote Start)

Once you have the code, you can figure out what part is acting up. According to repair data from shops across the country, here are the usual suspects that kill your remote start:

1. Oxygen (O2) Sensor

This is a sensor in your exhaust that measures how much unburned oxygen is coming out of the engine. If it goes bad, the car burns too much gas. It's a very common reason for the light to pop on.
The Fix: Usually replacing the sensor. It’s often a DIY job if you're handy with a wrench.

2. Mass Airflow Sensor (MAF)

This measures the air coming into the engine so the computer knows how much fuel to inject. If this gets dirty or breaks, the car runs rough.
The Fix: Sometimes just cleaning it with a special spray ($10) fixes it. Otherwise, it needs to be replaced.

3. Catalytic Converter

This is the expensive one. If your O2 sensor or spark plugs have been bad for a long time, they can ruin the catalytic converter. This part cleans up your exhaust fumes.
The Fix: This usually requires a mechanic and can be pricey.

4. Spark Plugs and Wires

If your spark plugs are old, the engine might "misfire." This feels like a stutter when you accelerate. A misfire is dangerous for the engine, so the computer will definitely disable remote start for this.
The Fix: A tune-up. New plugs and wires usually solve it.

Can I Bypass the Check Engine Light?

I get asked this alot. "Can I just trick the car so I can use my remote start?"

The short answer is no.

The remote start system checks the status of the "MIL" (Malfunction Indicator Light) before it engages. If that status is "ON," the command is ignored. You cannot bypass this without fixing the issue or clearing the code.

Now, technically, you can clear the code with a scanner just to get the light off temporarily. If you clear the code, your remote start will work... for about 10 minutes. As soon as the car runs a self-check and sees the problem is still there, the light comes back on and the remote start gets disabled again. It’s a temporary band-aid, not a fix.

How to Clear the Light (To Test It)

If you've fixed the problem (like tightened the gas cap or replaced a sensor) but the light is still on, you might need to force the system to reset.

The Scanner Method (Preferred)

Use that OBDII scanner we talked about. There is usually a button that says "Erase Codes" or "Clear DTCs." Hit that. The light turns off. Try your remote start-it should work immediately.

The Battery Method (Old School)

If you don't have a scanner, you can disconnect the negative (black) battery terminal for about 15 minutes. This cuts power to the computer and wipes its temporary memory.

Warning: This resets everything. Your radio presets, your clock, and sometimes your seat memory will be gone. Also, on some newer cars, disconnecting the battery can cause other weird electrical glitches, so check your owner's manual first. But usually, it works fine to reset the check engine light.

Specific Car Brands and Their Quirks

While almost all brands do this, here is what you need to know about specific manufacturers:

Chevy / GMC / Cadillac

GM vehicles are very strict about this. If there is any stored code in the ECM (Engine Control Module), remote start is dead. Even if the light isn't actively on but there is a "pending" code, it might still fail. You'll usually see the parking lights flash just once, and then nothing happens.

Ford

Ford is similar. If you try to remote start a Ford F-150 or Explorer with a CEL on, the horn might honk once to tell you "No," or it just won't do anything. Ford also disables remote start if the battery voltage is too low, so check your battery health too.

Toyota / Honda

Japanese manufacturers are huge on safety. On many newer Toyotas, if the check engine light is on, it also disables the Traction Control and Cruise Control along with the remote start. It’s like the car goes into total lockdown until you fix it.

When to Call a Pro

Look, I love fixing things myself, but sometimes you gotta know when to fold 'em. You should go to a mechanic if:

• The light is flashing: A flashing check engine light means a severe misfire that is actively damaging your engine. Do not try to remote start it. Do not pass Go. Tow it to a shop.
• You smell rotten eggs: This usually means your catalytic converter is clogged or overheating.
• The car runs terrible: If it's shaking, stalling, or making loud noises, the remote start being disabled is the least of your worries.

Preventing This in the Future

To keep your remote start working all winter when you actually need it, keep up with basic maintenance.

1. Change your oil on time. Old oil can trigger sensor issues.
2. Replace your air filter. A clogged filter messes with the Mass Airflow Sensor.
3. Don't top off your gas tank. When the pump clicks off, stop pumping. Overfilling forces raw gas into the EVAP canister, which ruins it and triggers the light (and kills your remote start).

Conclusion

I know it's super frustrating. You paid for a car with remote start, and now you're freezing in the driver's seat waiting for the windshield to defrost. But just remember, the car isn't trying to annoy you-it's trying to save you from blowing up the engine.

Start with the gas cap. If that doesn't work, get the code read at a parts store. Fix the issue, clear the code, and you'll be back to a warm car in no time.

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Frequently Asked Questions

Does a check engine light always disable remote start?

On about 95% of vehicles made after 2010, yes. It is a standard safety protocol programmed into the car's computer. If you have an aftermarket remote starter (like a Viper or Compustar), it might still work because it bypasses the car's main computer logic, but factory remote starts will almost always fail.

Can I just disconnect the battery to fix it?

Disconnecting the battery will turn the light off temporarily and might let you remote start the car once or twice. However, if you haven't fixed the actual problem (like the bad sensor), the light will come back on as soon as you drive, and the remote start will stop working again.

How much does it cost to fix?

It depends entirely on the code.
Loose gas cap: Free.
New gas cap: $15.
Mass Airflow Sensor cleaning: $10 (DIY).
O2 Sensor: $150–$300.
Catalytic Converter: $1,000+.

Will my remote start work if the tire pressure light is on?

Usually, yes. The Tire Pressure Monitoring System (TPMS) light is separate from the engine computer. However, some very new, high-tech cars might disable remote features for any warning light, but generally, tire pressure won't stop the engine from starting remotely.

I fixed the problem, but the remote start still won't work. Why?

You probably need to clear the "Permanent Codes" or History codes. Even if the light is off on the dashboard, the computer might still remember the error. Use a scanner to clear all codes, or drive the vehicle for a few days so it completes its "drive cycles" and clears itself.