Can you drive with the check engine light on?

Solid vs flashing: the first thing to look at

A solid check engine light means the engine computer has confirmed a fault related to emissions or engine management. Many of these faults, such as small EVAP leaks or a slow oxygen sensor, do not affect how the car drives in the short term. You can usually keep driving carefully, but you should read the code within days, not months.

A flashing check engine light means an active misfire severe enough that unburned fuel is going into the exhaust. That fuel can overheat and damage the catalytic converter, which is an expensive part. Reduce load, avoid hard acceleration, and get off the road when you safely can. See check engine light solid vs flashing and P0300 random misfire.

Other warning lights that change the answer

The check engine light is usually amber. Red warnings are more urgent. A red coolant temperature light or a gauge near the top means the engine is overheating. A red oil can means low oil pressure. Driving with either can cause serious engine damage within minutes, so stop the engine as soon as you can do it safely.

A battery or charging light means the alternator may not be charging. The car may run until the battery is drained, then stall. A brake system warning or a reduced power message, sometimes shown with a wrench icon, also deserves prompt attention. Check your owner's manual for what each light means on your vehicle.

Note.If the car stalls, loses steering assist, or loses braking feel, get safely off the road and call for help. Do not try to diagnose in traffic.

Simple checks you can do right away

Before you assume the worst, look at the easy things. If the light came on just after a fill-up, the gas cap is a common cause. See check engine light after getting gas.

1. 1

   Note whether the light is solid or flashing, and how the engine feels.

2. 2

   Check the temperature gauge and any red warning lights.

3. 3

   If you just got gas, remove and reinstall the gas cap until it clicks.

4. 4

   Check the engine oil level when the car is parked on level ground.

5. 5

   Read the codes with an OBD2 scanner, or have a parts store read them.

6. 6

   Look up each code and decide whether it is urgent.

Why reading the code matters

The light alone cannot tell you how serious the problem is. The code can. A code like P0456, a very small EVAP leak, is low urgency. A misfire code, a coolant temperature code, or a code related to the crankshaft position sensor such as P0335 can lead to stalling or engine damage and deserves fast attention.

A basic OBD2 scanner reads the code in a minute or two and also shows freeze frame data, which tells you the conditions when it set. Learn how in how to use an OBD2 scanner, and look up any code with the code decoder.

Find a scanner to read your code →

Risks of ignoring a solid light

Even when the car feels fine, ignoring the light has costs. While one fault keeps the light on, you will not notice when a second, more serious fault appears. A small problem like a lean condition (P0171) can lead to misfires over time. An ignored misfire can damage the catalytic converter and set P0420.

In states with emissions testing, a lit check engine light usually means an automatic fail. Fuel economy may also drop with some faults, such as a stuck thermostat (P0128) or a failed oxygen sensor.

• Hidden second faults go unnoticed
• Small problems can grow into catalyst damage
• Failed emissions inspection in testing states
• Possible lower fuel economy

Frequently asked questions

How long can I drive with the check engine light on? There is no fixed number. With a solid light and normal driving, many people drive for days while they get the code read. With a flashing light, stop as soon as it is safe.

Will the check engine light turn off by itself? Sometimes. If the fault goes away, the computer turns the light off after several good drive cycles. See how to clear a check engine light.

Is it safe to drive on the highway with the check engine light on? If the light is solid and the car drives normally, usually yes. If it is flashing or the car is losing power, avoid the highway.

Why is my check engine light on but the car runs fine? Many emissions faults do not affect drivability. See check engine light on but car runs fine.