Check engine light (CEL) or Service engine soon (SES)


Check Engine Light is on? It means your vehicle engine control unit (ECU) has diagnosed some kind of trouble such as the ignition, fuel injection or emission control is not working properly. It can be found under the dashboard, near the driver’s seat. From January 1996 Vehicles are supplied with OBD2 (On board diagnostics). OBD2 scanner retrieve data from the ECU and provides a good source of information when fixing problems inside a vehicle. There’s no other way to know what the light means without running a diagnostic scan on the system to determine the nature of the problem.

Useful links : OBD2 Scanner

When light is on the ECU accumulate engine trouble codes related to the problem, trouble codes can be scanned using a OBD2 scanner and used for further diagnosis. Trouble codes are numeric codes like P0XXX generic codes or P1XXX manufacturer specific codes.

Useful links : Trouble codes

To help identify the trouble, make a clear note of the conditions that occurred when the light came on. Accelerating or slowing down? Where you driving at a certain speed? Cold-engine? Shifting gears? Wet-engine?
Two Conditions of Check engine light:

  • Steady light (Indicates Minor problem, but don’t ignore it may lead to expensive repairs)
  • Flashing or Blinking (Indicates Major problem and needs immediate attention!)



Different auto brands and models have somewhat diverse names for the “service engine soon” or “check engine light” cautioning, also known as the “SES” or “CEL” cautioning. Some auto warnings just say “engine”, “check engine” or “service engine.”


“Service Engine Soon Light” is basically an emissions monitor there is no compelling reason to panic. “Red” cautioning lights that require a quick shutdown of the engine, The “yellow” or “orange” service engine soon light may mean something isn’t right with your anti-lock brake, there is a machine issue in your auto or emission system. Your auto is polluting and additionally performing underneath its plan potential.

Top 10 common check engine light reasons / causes


1) Replace oxygen Sensor (O2S) – 8.3% of CEL problem.

2) Inspect for loose gas cap and tighten or replace – 7.2% of CEL problem.

3) Replace catalytic converter with new OE catalytic converter – 6.7% of-CEL problem.

4) Replace ignition coils and spark plug’s if required – 6.1% of-CEL problem.

5) Replace spark plug Wires and spark plugs – 3.98% of CEL problem.

6) Replace mass air flow (MAF) sensor – 3.5% CEL problem.

7) Remove off market alarm system – 2.4% of CEL problem.

8) Inspect for faulty vacuum hose’s and repair if required – 2.3% of CEL problem.

9) Replace exhaust gas recirculation (EGR) valve and clean all exhaust gas recirculation ports – 2.2% of CEL problem.

10) Inspect battery and charging system and repair/replace as necessary – 2% of CEL problem.

Useful links : Reasons for check engine light



1) Oxygen Sensor – Upto 40%

2) Gas Cap – Upto 1%

3) Catalytic Converter – Upto 25%

4) Ignition Coil – Upto 22%

5) Spark Plug & Wire – Upto 3%

Drivers usually ignore CEL but this negatively affect vehicle mileage (fuel economy) if you ignore it for a long and keep driving.




Timely repair/service save cash

Giving careful consideration to little issues and suggested support timetables broaden the life of your auto and minimize check engine light related repairs.