IS THE CEL LIT OR FLASHING?
CAN I CHECK MY OWN LIGHT?
5 REASONS YOUR CHECK ENGINE LIGHT MAY BE ON.
FAILED OXYGEN (O2) SENSORS.
Oxygen sensors also live a hard life in +800 degree exhaust temps and are prone to fail once over 80,000 miles. It’s important to note here that there are a multitude of engine codes where the oxygen sensor is telling us something is wrong, but that DOES NOT mean that the oxygen sensor is bad. Be careful determining that a sensor is truly at fault, as opposed to determining something else is happening. This cannot be more apparent than in the ever-popular PO420 / PO421 engine code, which is detailed HERE.
What happens if I don’t replace it?
- Your engine will burn more fuel than needed
- You will lose fuel economy, and get fewer miles per gallon
- Faulty sensor(s) can cause damage to your spark plugs and catalytic converter
GAS CAP IS LOOSE, DAMAGED, OR MISSING – EVAP.
What happens if I don’t replace it?
- You can lose fuel through evaporation
- Your recirculation system will not function properly
- You will have to stare at the CEL until it’s fixed
BAD CATALYTIC CONVERTER.
What happens if I don’t replace it?
- Your vehicle will not pass an emissions test
- You will experience reduced performance and fuel economy
- Whatever caused the converter to fail initially will continue to get worse, possibly causing engine failure
MASS AIRFLOW SENSOR OR INTAKE TRACT
- A faulty MAF sensor can cause rich or lean conditions, which can lead to further failures of other parts
- You will experience reduced performance and fuel economy
MISFIRES.
- Defective ignition coil: (either DIS or coil-on-plug). A quick trick to determine if a coil is causing a misfire is to simply move the coil and swap with another on the engine. If you have a #2 misfire and move the #2 coil to #4, for example, then the misfire moves to #4, you know the coil is suspect.
- Defective fuel injector: If a fuel injector fails to deliver the proper amount of fuel to a cylinder, you will have a misfire. Unlike swapping the ignition coil with a neighboring coil, a fuel injector is more difficult to move.
- Vacuum leak: Vacuum leaks often cause multiple cylinder misfires, or lean running conditions. They also can be very difficult to diagnose.
- Worn spark plugs and/or wires: Sometimes, spark plugs can go far past their life cycle, and fail, causing a misfire. On vehicles with spark plug wires, a defective wire or wires can also cause this.
- Bad compression: More serious, a burnt or bent valve, worn piston rings, or valve timing that is off will cause a misfire as well. These issues will all become apparent during an engine compression test.
- You will experience poor performance (reduced power, engine missing) and reduced fuel economy
- The misfire will only get worse, and will lead to mechanical failure in the engine