Hyundai Check Engine Light on

Hyundai Check Engine Light

 HUB: Hyundai  Updated Thursday Dec 14, 2017

Hyundai is one of the most reliable car manufacturers out there. The fact of the matter is however that even Hyundai cars can turn on the Check Engine Light (CEL) if there is an engine or emissions problem. If your Hyundai check engine light turned on don't panic. We will show you how to use a Level 1 OBD-2 Scanner some of which cost as little as $20, to read and clear Hyundai check engine light. You may be surprised, but the check engine light may come on for something as simple as the gas cap being loose.

Hyundai check engine light can be triggered for several reasons which we discuss in this guide. 

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1. Why is my Hyundai Check Engine Light on? 

In a Hyundai, the check engine light comes on as soon as the onboard diagnostic system (OBD) detects that there’s an issue with the way the engine operates or Evaporative Emission Control System (EVAP) which is used to prevent gasoline vapors from escaping into the atmosphere. A fault code stored in the Engine Control Unit (ECU), explains what caused the check engine light to come on.

If the ECU has detected a fault code and triggered the Check Engine Light (CEL) / Service Engine Light, don't necessarily assume that there is an engine problem. The problem could be an emission related problem and the car may drive fine. Still, don't ignore the CEL light. Always read the fault codes via the OBD2 port which you can perform yourself or have an auto mechanic.

An auto mechanic or dealer technicians use specialized equipment (OBD2 scanners) to read the code from the car’s computer (ECU) via the OBD port. This is a simple procedure that Hyundai owners can perform themselves without any prior experience. 

check engine light on hyundai santa feIf the check engine light is on, you have a couple of options.

  1. The most expensive route would be to take your Hyundai to an auto mechanic and pay over $100 for check engine diagnosis. They will read the codes and tell you what is wrong. 
  2. This procedure is so easy, you can perform yourself right on your driveway. All you need is a code reader which can be purchased at any auto parts store or online. Some auto parts stores may even read the codes free of charge. If you don't have an OBD-II code reader consider getting one as they are very useful and can save you hundreds of dollars on car diagnosis. Read this article for tips on Choosing an OBD-II diagnostic scanner for DIYers.
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2. How to read Hyundai check engine codes

Diagnosing Hyundai check engine codes is easy. Any Hyundai owner can read Hyundai codes, right in their driveway. No need to drive to the dealership or pay $100+ for such a simple procedure. 

What you will need


Step 1

hyundai sonata check engine light on

Locate the OBD-II port. This is a 16-pin port located under the dashboard on the driver's side. 

Step 2

hyundai codes for check engine light onPlug the scanner into the OBD-II 16-pin port. 

Step 3

turn hyundai igntion on to diagnose check engien light on

Turn the key to on. All the dash lights should turn on. Don't start the engine. 

Step 4

hyundai check engine light on clear codes

Scanner turns on. Hit 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 on Hyundai cars. 

Step 5

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.

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3. Common Fault Codes

EVAP Codes

Typically when Hyundai check engine is on but 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 atmosphere from the fuel tank and fuel system. 

how to clear hyundai check engineIn 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 a 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. You don't need a scanner to reset it. 

Related fault codes:

  • P0440 Evaporative Emission Control System Malfunction.
  • P0444 Evaporative Emission Control System Purge Control Valve Circuit Open

  • P0422 Main Catalyst Efficiency Below Threshold (Bank 1)

  • P0420 Catalyst System Efficiency Below Threshold (Bank 1)

Hyundai check engine light flashing/blinking

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 engine misfire. Replacing the spark plugs and spark plug wires is all that you need to do 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:

  • P0300 Random/Multiple Cylinder Misfire Detected

  • P0301 Cylinder 1 Misfire Detected

  • P0302 Cylinder 2 Misfire Detected

  • P0303 Cylinder 3 Misfire Detected

  • P0304 Cylinder 4 Misfire Detected

Check Engine Light on / No Acceleration

what does check engine light mean on hyundai sonataIf 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

Hyundai Check engine light and ESC on

If you both the check engine light and the ESC light come on this means that the accelerator pedal position switch has failed. In such cases, the car will loose all power. Pressing the gas pedal to the floor will not have the desired effect on engine RPMs. The car won't accelerate. Hyundai sells a redesigned accelerator pedal position switch that should fix this problem. Usually, you can only get your car up to 20 MPH. Try restarting the car as this may fix this problem temporarily. Replacing the sensor at the dealer or a repair shop costs between $200-$450 USD.

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4. Common causes of Hyundai Check Engine Light

Below you will find a list of common problems that trigger Hyundai check engine light. Do not start replacing parts without first properly diagnosing the problem. 

Spark Plugs

check engine light on due to old spark plugs

Engine misfires are an extremely common problem and while there are many possible causes, the most common causes are spark plugs, engine vacuum system leaks, ignition system faults, and dirty or worn fuel injectors.

You may not even know that you need to change the spark plugs at the recommended interval. Spark plug interval depends on the material of the spark plug tip. It could be 30,000 60,000 or even 100,000 miles. Changing the spark plugs and the spark plug wires (when applicable) is considered standard maintenance on all vehicles. If you fail to change them, not only will fuel economy decrease, but you can get a check engine light. If you ignore the light for a prolonged period of time, the spark can cause catalytic converter problems which are very expensive to repair.

Change the spark plugs on time or risk spending more money on replacing other perfectly fine parts.

Possible symptoms:

  • CEL light will be ON

  • Code P0300 as well as many possible generic codes may be present
  • Random misfires
  • Engine idling may be rough, erratic, or may fluctuate
  • Engine may show some power loss
  • Catalytic converter damage may occur if the fault is not corrected
  • Dilution of the engine oil may occur
  • Fuel consumption may increase

Probable causes:

Apart from the probable causes listed above, other possible causes could involve almost any part, component, system, sub-system, or control module that is implicated in the engine and fuel management systems.


Possible solutions and remedies are dependent on which codes are present. However, diagnosing and repairing codes in the order in which they were stored is recommended, since many codes set as the result of codes that precede them. Thus, repairing codes from the top down often resolves additional codes as well.

Can I fix it?

Repairing this code is NOT recommended for novice DIY mechanics unless it is a simple job as replacing the spark plugs. Finding some faults often requires advanced diagnostic equipment and above average diagnostic skills.

Related Fault Codes

  • P0300 Random/Multiple Cylinder Misfire Detected

  • P0301 Cylinder 1 Misfire Detected
  • P0302 Cylinder 2 Misfire Detected
  • P0303 Cylinder 3 Misfire Detected
  • P0304 Cylinder 4 Misfire Detected
  • P0305 Cylinder 5 Misfire Detected
  • P0306 Cylinder 6 Misfire Detected
  • P0307 Cylinder 7 Misfire Detected
  • P0308 Cylinder 8 Misfire Detected
  • P0309 Cylinder 9 Misfire Detected

Oxygen Sensoroxygen sensor o2 triggering check engine light esc off

By far and away the most common cause of a check engine light, if a failed oxygen sensor. The car may run fine or have performance issues due to O2 sensor sending wrong information to the ECU. Failed oxygen sensors can cause the ECU to make the engine run to reach or lean. If the engine doesn't run right it can result in up to 30% decreased fuel economy. Replacing the oxygen sensor can be easier than changing your oil or extremely difficult that required expert skills. It all depends on how easy it is to access the oxygen sensor on your car. Generally, four cylinder cars are easy where V6 and V8 can be challenging. Regardless of which engine you have, you will need an oxygen sensor socket and follow these tips to get out a stuck oxygen sensor


Be caution when diagnosing oxygen sensor codes. The oxygen sensor itself may be operating properly but the underlaying issue could be the catalytic converter. 

Related Codes

  • P0141 - O2 Sensor Heater Circuit Malfunction Bank 1 Sensor 2
  • P0057 - Cylinder 2-3 Heated Oxygen Sensor Rear Heater Control Circuit Low
  • P0138 - Oxygen Sensor Circuit High Voltage Bank 1 Sensor 2
  • P0155 - O2 Sensor Heater Circuit Malfunction Bank 2 Sensor 1
  • P1131 - Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 1
  • P0131 - O2 Sensor Circuit Low Voltage Bank 1 Sensor 1

Ignition Coilcheck engine light on due to bad ignition coil

Ignition coils are another common cause of Check Engine Light. They don't need to be replaced as often as spark plugs. Typically you can replace just the failed ignition coil. Ideally, you may want to replace them all at the same time, If you don't another coil can fail two weeks, five months or one year down the road.

  • P0357 P0355 P0358- Ignition Coil A B C G E H Primary/Secondary Circuit Malfunction
  • P2307 Ignition Coil 'C' Primary Control Circuit High
  • P2300 Ignition Coil 'A' Primary Control Circuit Low
  • P1365 Ignition Coil Secondary Circuit Failure

Mass Air Flow Sensor - MAFmass air flow code and check engine light stays on

The MAF sensor is on Top 3 items when it comes to causes of a check engine light. The MAF sensor is more vulnerable and susceptible to failure in dry and dusty climates, as well as snow and ice. Replacing the mass air flow sensor is very simple and usually takes less than 20 minutes. Keeping the air filter clean prolongs the MAF sensor’s life by a lot and avoid air filter that needs to be oiled. 


Related Codes

  • P0100 Mass Air Flow Circuit Malfunction
  • P0102 Mass Air Flow Circuit
  • P010C - Mass Air Flow Sensor Bank 2 Circuit Low Input
  • P0101 - Mass Air Flow Sensor Performance
  • P0104 - Mass or Volume Air Flow Circuit Intermittent
  • P0103 - Mass or Volume Air Flow Circuit High Input

Catalytic Converter

car shaking check engine light onNewer cars don’t experience this issue that often, but as you start to put some miles on your car the catalytic converter may need to be replaced once you hit 100k miles. Technically catalytic converters are not "wear and tear" items, but they do fail and in some cases as early as 60k miles. Life of catalytic converter is shortened if you are not maintaining the car properly. It’s a very expensive car repair, probably the costliest one on this list. To replace the catalytic converter you will spend around $400-$800 for universal catalytic converter If you decide to get the work done at the dealer plan on well over $1000. Universal catalytic converters work just as well by the way, as long as your mechanic knows how to weld one properly. 

Variable Valve Timing

variable timing cause of check engine light

The VTEC (Variable Valve Timing and Lift Electronic Control) uses pressurized engine oil to vary the valve timing relative to a base setting. The VTEC system allows for improved engine performance throughout the engines’ operating range, while reducing fuel consumption and exhaust emissions at the same time. A failure of the system occurs when the actual oil pressure differs from the oil pressure that is required to operate the variable valve timing mechanism.  

Possible symptoms:

  • CEL light will be ON
  • Code P1259 is likely to be present
  • Engine may misfire at some engine speeds
  • Engine may lose power at some engine speeds
  • Fuel consumption may increase noticeably

Probable causes:

  • Defective oil flow control solenoid
  • Defective VTEC oil pressure switch
  • Dirty or degraded engine oil
  • Use of unsuitable engine oil
  • Mechanical failure of the VTEC system
  • Low engine oil levels
  • Electrical control circuit faults


  • Replace defective components
  • Replace engine oil
  • Diagnose and repair electrical faults

Can I fix it?

This is a moderately difficult repair that requires at least a basic knowledge of automotive diagnostics and of variable valve timing systems in particular. This repair is NOT recommended for novice DIY mechanics.

MAP too high/low (P1129, P1128)

The MAP sensor measures pressure or vacuum in the inlet manifold while the engine is running. The PCM uses input data from the MAP sensor to control the air/fuel mixture, in conjunction with input data from the oxygen or air/fuel ratio sensor(s) and sometimes exhaust gas temperature and Nox sensors.

Possible symptoms:

  • CEL light will be ON.
  • One or more of the following codes may be present:  P1129, P1128, or P0068
  • In some cases, a hard or no start condition will be present
  • Idling speed may fluctuate, or the engine may not idle at all
  • The engine may stall unexpectedly at low engine speeds
  • Fuel consumption may increase noticeably

Probable causes:

  • Defective MAP sensor
  • Defects in related sensors and control circuits
  • Open circuits, short circuited wiring, or damaged wiring in the MAP sensor wiring harness
  • Open or short circuited wiring in the reference voltage circuit.


  • Replace the MAP sensor
  • Diagnose and repair electrical faults

Can I fix it?

 This is an easy DIY fix that does not require any special tools or advanced knowledge. You only need a repair manual/wiring diagram, a digital multimeter, and some basic tools.

EVAP System Leak Detected (Fuel Tank System)(P1456)

The EVAP (Evaporative Emissions Control) system is designed to capture and retain fuel vapors before they can escape into the atmosphere. In a fully functional system, fuel vapors are transported to engine to be combusted as part of the air/fuel mixture without any fuel vapors escaping into the atmosphere.

Possible symptoms:

  • CEL light will be ON

  • Code P1456, and several other generic codes may be present
  • Vehicle may not pass an emissions test
  • PCM will not complete all readiness monitors and self-diagnostic tests

Probable causes:

  • Loose gas cap
  • Defective purge and/or vent solenoids
  • Perforated or leaking vacuum and fuel vapor lines
  • Electrical control circuit faults


  • Tighten or replace gas cap
  • Inspect and replace damaged vapor and vacuum lines
  • Identify and replace defective control solenoids/valves
  • Diagnose and repair electrical faults

Can I fix it?

Depending on the nature and site of the leak, this repair can vary from moderately difficult to very challenging, and is not recommended for novice DIY mechanics that do not possess at least some degree of mechanical knowledge or skills.

Idle Air Control Valve Circuit Failure (P1508)

The purpose of the Idle Air Control valve is to regulate and control the amount of air the engine requires to idle at the speed set by the PCM. Note that electrical control circuit failures and engine vacuum system leaks are far more common than failures of the IAC valve itself.

Possible symptoms:

  • CEL light will be ON
  • Code P1508 is likely to be present
  • Idle speed may be higher or lower than the desired idle speed
  • Idling speed may fluctuate
  • Gear shift into “D” or “R” may be harsh
  • Engine may stall at low idling speeds

Probable causes

  • Electrical control system faults
  • Unmetered air that enters the engine through vacuum leaks


  • Locate and repair engine vacuum system leaks
  • Diagnose and repair electrical control system faults

Can I fix it?

This repair is moderately easy, and no special tools apart from a wiring and/or vacuum diagram and usually, only a digital multimeter are required.

Read codes from your using the OBD-2 port under the dashboard. This is a 16-pin port where you plug a scanner and retrieve the codes. 

Fuel Injector

In some cases, the fuel injectors are to blame for the check engine light. The reason for the failure is simple. Fuel injectors spray fuel into the engine, usually under high pressure. Not only can they fail and not deliver the needed amount of fuel, but they can get clogged up and not work at all. This is most often the result of poor fuel quality and/or driving the car with the reserve light on frequently. Replacing the faulty injector (injectors) will solve the issue.

EGR Valve

Replacing the EGR valve and cleaning all of the EGR ports can be quite expensive but is a must in ensuring your engine runs as smoothly as long as possible. It’s common for EGR components to fail, especially in diesel cars. If you’re lucky to solve the issue with a thorough cleaning of the EGR ports, you may not need to replace the entire valve.

The purpose of the EGR valve is to control both the timing and the amount of exhaust gas that is allowed to mix with the air/fuel mixture. Recirculation of exhaust gas lowers combustion temperatures, which in turn, reduces or even eliminates the formation of harmful exhaust emissions such as nitrous oxides. 

Possible symptoms:

  • CEL light will be ON
  • Code P1491 is likely to be present
  • In some cases, no drivability symptoms may be present
  • In some cases, some power loss may be present upon acceleration
  • In some cases, the engine may misfire or run roughly at some engine speeds

Probable causes:

  • Defective EGR valve
  • Excessive build-up of carbon deposits in the EGR valve
  • Electrical control circuit faults
  • Faults or leaks in the vacuum control circuit


  • Inspect and clean or replace EGR valve
  • Diagnose and repair electrical or vacuum control system faults

Can I fix it?

This repair varies from easy to moderately difficult. No special tools or skills are usually required.


The thermostat is constantly under stress. Apart from maybe the engine internals, it’s one of the most used components under the hood. So it’s no surprise that it’s one of the first components to let go as well. The good thing is that it’s a relatively inexpensive part to replace.

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