Why is my engine light flashing on my Toyota Highlander?

The flashing engine light on a Toyota Highlander almost always signals a severe engine misfire that can overheat and damage the catalytic converter. If you see it, pull over safely as soon as you can and arrange diagnostic service promptly.

What the flashing light means

The malfunction indicator lamp (MIL) flashing is a urgent warning from the engine management system. It usually points to a misfire or a critical fault in the fuel, ignition, or exhaust systems that, if left unchecked, can harm the catalytic converter and significantly reduce engine performance.

Key signs to watch for

In addition to the flashing light, you may notice rough running, loss of power, hesitation during acceleration, a strong fuel odor, or overheating warnings. If any of these symptoms occur, treat the situation as urgent and seek service quickly.

Common causes in a Highlander

The following are the most frequent culprits behind a flashing check engine light on Toyota Highlanders. The exact cause can only be confirmed with a diagnostic scan.

• Severe engine misfire in one or more cylinders


• Ignition system problems, such as faulty spark plugs or ignition coils


• Fuel delivery issues, including a failing fuel pump or clogged injectors


• Vacuum leaks or intake manifold leaks


• Exhaust or emissions sensor problems (for example, oxygen sensors or the mass airflow sensor)


• Catalytic converter overheating or damage caused by a prolonged misfire


• Less common: a loose or damaged gas cap that interferes with the evaporative emissions system (can trigger codes but is less likely to cause a flashing light)

Because these problems vary in severity, a precise diagnosis requires scanning the vehicle’s computer with an OBD-II tester and reading the stored fault codes.

Immediate steps to take

To protect your Highlander and prevent catalytic converter damage, follow these steps right away.

1. Safely pull over and park as soon as you can do so without endangering yourself or others.


2. Turn off unnecessary electrical loads and, if advised by the owner’s manual, let the engine rest briefly.


3. Check for obvious issues like low oil or coolant levels and address only if safe to do so.


4. Avoid driving long distances or at high speeds; a flashing light means a fault that could worsen under load.


5. Call roadside assistance or arrange a tow to a trusted mechanic or Toyota service center.

Once at a shop, technicians will begin diagnostics to identify the exact cause and determine whether immediate repairs are required.

Diagnosis and repair

Trained technicians will typically perform the following:

• OBD-II scan to retrieve fault codes and freeze-frame data


• Visual inspection of ignition components (spark plugs, coils), wiring, fuses, and sensors


• Compression test to assess engine health and detect misfires not caused by fuel or ignition


• Fuel system pressure test and injector flow checks


• Vacuum and intake system leak checks, including hose and gasket inspection


• Exhaust and catalytic converter evaluation, including sensor diagnostics

Common repairs may include replacing faulty spark plugs or ignition coils, cleaning or replacing fuel injectors, repairing vacuum leaks, updating or replacing sensors, or in some cases addressing catalytic converter damage. Exact work depends on the fault codes and vehicle history.

Hybrid Highlander considerations

For Highlander models equipped with the hybrid drivetrain, the check engine light can reflect issues in either the gasoline engine, the hybrid battery system, or the power electronics. A flashing light still indicates a fault that requires prompt diagnosis, and hybrid repairs can involve specialized procedures and safety considerations.

Safety and towing considerations

If the vehicle is behaving oddly in hybrid mode—unusual noises, reduced power, or abnormal battery behavior—online diagnostic support and possible towing are recommended. Hybrid systems require technicians trained in high-voltage safety.

Prevention and maintenance

Regular maintenance helps prevent many causes of a flashing engine light. Follow Toyota’s recommended service intervals and address maintenance items promptly.

• Use quality fuel and avoid frequent short trips that prevent proper engine warm-up


• Replace spark plugs and ignition components at recommended intervals


• Keep sensors clean and functioning; address issues with oxygen sensors, the MAF sensor, and the EGR valve as needed


• Check for vacuum leaks and cracked hoses


• Ensure the evaporative emissions system is intact and the gas cap seals properly


• Check for software updates or recalls with a dealer

Being proactive about diagnostics, timely maintenance, and addressing fault codes promptly reduces the risk of further damage and can save on repair costs.

Summary

A flashing check engine light on a Toyota Highlander is a warning of a potentially serious engine problem, most commonly a misfire that can harm the catalytic converter. Do not ignore it: pull over safely, have the vehicle diagnosed with an OBD-II scanner, and follow through with the necessary repairs at a qualified shop. Hybrid models require careful handling and possibly high-voltage safety considerations, but the core message remains: prompt attention minimizes risk and cost.

Can I drive my car with the check engine light blinking?

No, you should not drive a car with a blinking check engine light. A flashing light indicates a serious engine problem, like a misfire, and continuing to drive can cause severe damage to internal engine parts and the catalytic converter. The safest course of action is to pull over as soon as it is safe, turn off the car, and have it towed to a mechanic.
 
This video explains what to do when your check engine light is flashing: 1mproclaimliberty2000YouTube · Dec 13, 2019
Why a blinking light is dangerous

• Severe engine misfire: The most common cause is a misfire, where one or more cylinders fail to ignite the air-fuel mixture correctly. 
• Risk of expensive damage: Driving with a misfire can cause the unburned fuel to enter the exhaust system, which can overheat and damage the catalytic converter, leading to very expensive repairs. 
• Safety concerns: A serious misfire can cause engine hesitation or a lack of power, making the vehicle unsafe to drive. 

What to do immediately

1. Pull over safely: As soon as you can do so without causing a hazard, pull over to the side of the road. 
2. Turn off the engine: Shut off the engine to prevent further damage. 
3. Call for a tow: Do not attempt to drive the car. Have the vehicle towed to a mechanic for diagnosis and repair. 

This video demonstrates how to diagnose and fix a flashing check engine light: 43sArrow GearheadYouTube · Aug 22, 2024

How serious is a flashing engine light?

A flashing check engine light is a warning that there is an issue with your vehicle's engine or emissions system. If you ignore the warning, you could end up causing further damage to your car's engine, which could result in costly repairs.

What is the most common cause of a flashing check engine light?

The most common cause of a flashing check engine light is an engine misfire, which is a problem with the ignition or fuel delivery systems. A misfire can be caused by issues like worn spark plugs, faulty ignition coils, or clogged fuel injectors. It's important to address this immediately, as it can cause expensive damage to your catalytic converter if ignored.
 
Common causes of a flashing check engine light

• Engine Misfire: This is a failure in one or more cylinders to ignite the fuel-air mixture. 
  • Ignition system problems: This includes worn or fouled spark plugs, failing ignition coils, or bad spark plug wires. 
  • Fuel system issues: This can be caused by clogged fuel injectors, a bad fuel pump, or other fuel delivery problems. 
• Catalytic converter problems: A severe misfire can damage the catalytic converter, which is an expensive part to replace. 
• Sensor malfunctions: Faulty oxygen sensors, mass air flow sensors, or crankshaft position sensors can lead to misfires by providing the wrong data to the engine's computer. 
• Vacuum leaks: Leaks in the vacuum system can disrupt the air-fuel mixture and cause misfires. 
• Other issues: A loose or damaged fuel cap can sometimes trigger the light, though it is less common for a flashing light. 

What you should do

• Pull over safely: and turn off the engine as soon as you can. 
• Avoid hard acceleration: and drive cautiously if you must move the vehicle. 
• Get the car inspected: by a qualified mechanic immediately. 
• Do not ignore the light: Driving with a flashing light can lead to more significant and costly engine damage. 

Why is the check engine light blinking on my Toyota Highlander?

This blinking light usually indicates a severe engine misfire allowing unburned fuel to be dumped into the exhaust system. There it can quickly raise the temperature of the catalytic converter to a point where damage is likely, requiring an expensive repair.