When your Hyundai check engine light comes on, it means the Onboard Diagnostic System has detected a problem with the engine, emission, or transmission. A fault code gets stored in the Engine Control Module (ECM) and retrieved with a diagnostic scanner via the OBD-II port under the dashboard.
If the ECM, sometimes called ECU, has detected a fault code and triggered the Check Engine Light (CEL) / Service Engine Light, don't necessarily assume an engine problem.
The problem could be emission-related, and the car may drive fine.
The diagnostics process's first step is to read the fault codes via the OBD-II port under the dashboard.
You can read the codes yourself or have an auto mechanic.
An auto mechanic or dealer technicians use specialized equipment (OBD-II scanners) to read the code from the car's computer (ECU) via the OBD port.
Diagnosing Hyundai engine fault codes is easy.
A Hyundai owner can read Hyundai engine fault codes using an OBD-II scanner connected to the OBD-II port under the dashboard (see instructions below).
- Locate the OBD-II port. This is a sixteen-pin port located under the dashboard on the driver's side.
- Plug your OBD2 scanner into the OBD-II 16-pin port.
Turn the key on. All the dash lights should turn on. Don't start the engine.
The scanner turns on. Hit the SCAN or READ button on your OBD-II scanner. You will see fault codes, such as P0300. Write down the code and do research online on what those codes mean for Hyundai cars.
Read fault codes.
Fix the problems you found in step five, reconnect the scanner, and select Clear Fault codes.
Fix the problem that caused the check engine light. You can use the scanner to clear the code or drive the car for a couple of days, and the light will turn off after four or five driving cycles.
Common problems that trigger the check engine light on a Hyundai
Typically when the Hyundai check engine is on, but the car drives fine, you most likely have an Evaporative Emission Control System (EVAP) code.
EVAP is used to prevent gasoline vapors from escaping into the fuel tank and fuel system atmosphere.
In many cases that the check engine light turns ON in a Hyundai (Elantra, Sonata, Santa Fe, Accent), the car may still drive perfectly fine. This happens when you have an emissions-related problem.
The problem here may be something as simple as a loose gas cap.
Retightening or replacing the gas cap often will fix the check engine light.
If the problem is a loose or defective gas cap and you address that problem, the check engine light will turn off on its own, usually in a couple of days.
Related fault codes:
If your Hyundai check engine light is flashing and the car is shaking, that means that you have a serious engine malfunction, and you should avoid driving your car.
Check engine light flashing and blinking is a result of an engine misfire.
Replacing the spark plugs and spark plug wires is all you need to fix this problem.
In some cases, the check engine light may flash due to a bad ignition coil as well.
All these are easy and inexpensive repairs and can be performed by any DIYer.
Don't continue to drive a Hyundai that has triggered the check engine light and is shaking; you may cause serious damage to the engine.
Not only that, but if you are driving in heavy traffic, your engine will overheat.
Related fault codes:
If your Hyundai will not accelerate and the check engine light is on, it is very likely that a faulty throttle position sensor.
Under these conditions, the car will barely move or not accelerate at all.
Replacing the throttle position sensor is easy and can be completed by any DIYer in less than one hour.
Fault codes related to Hyundai CEL on, the car won't accelerate.
P2135 Throttle/pedal position sensor/switch A/B voltage correlation
P2135 OBD-II Trouble Code: Throttle/Pedal Position Sensor/Switch A/B
P2106 FORD Throttle Actuator Control System - Forced Limited Power
P2127 Throttle/Pedal Position Sensor/Switch 'E' Circuit Low
P2138 Throttle/Pedal Position Sensor/Switch 'D'/'E' Voltage
P2101 P0222 P0123
If both the check engine light and the ESC light come on, this means that the accelerator pedal position switch (eBay link) has failed.
In such cases, the car will lose all power.
Pressing the gas pedal to the floor will not change engine RPMs. The car won't accelerate, but you can get your car up to 20 MPH.
Try restarting the car as this may fix this problem temporarily.
Hyundai sells a redesigned accelerator pedal position switch that should fix this problem.
Replacing the sensor at the dealer or a repair shop costs between $200-$450.
Installing a used Hyundai Accelerator Pedal (eBay link) is another possible solution.