Home > 5 Most Common OBD-II Codes

5 Most Common OBD-II Codes

We recommend car health monitoring, but there are times when monitors can be downright frustrating. The monitoring systems we recommend do provide you with insight into your car’s check engine light causes.

But if you go to the store and purchase an OBB-II scanner and hook it up, you’ll be presented with dreaded OBD codes.

If you were lucky enough to own a car before the Internet and any of these neat devices were made, you would plug your scanner into your vehicle and be presented with a code. These codes are still used at dealerships and mechanics today.

The code will correspond to an engine issue, but try deciphering what P0171 means – it’s not descriptive.

Today, I am going to go over each of the most common codes, in no particular order, and what these codes mean if they pop up on your scanner.

1. P0300 – P0305

Is your car shaky or starting to vibrate for no reason? The main issue normally has to do with the codes P0300 – P0305. The codes indicate that the engine is misfiring, and the misfire can relate to the vehicle’s cylinders.

Your vehicle has multiple cylinders, and this code means that one of more of the cylinders are misfiring.

When this code pops up, you may also notice that your fuel efficiency drops simply because the vehicle is not operating properly.

The vehicle monitors your crankshaft speed, and a misfire will be entered into the system when the speed of the crankshaft is slower than normal. If you have one of these codes, you’ll want to go to the mechanic and have the vehicle fully examined and repaired.

2. P0171 – P0175

Automobiles require just the right amount of oxygen to complete the combustion cycle. If the vehicle gets too much air or too little air, fuel efficiency drops and will also start emitting more emissions.

Cars have a variety of different sensors, and this code range has to do with the vehicle’s oxygen sensors.

The goal of the sensor is to monitor all of the oxygen that is exiting out of your vehicle’s exhaust system. If the levels are too high or low, the sensor will alert the computer which will make all of the necessary adjustments to optimize oxygen flow.

In the most severe of cases, your vehicle may stall due to not enough oxygen.

If this happens, you may be able to start the vehicle and make it to a mechanic before it stalls again. The oxygen sensors are vital to your vehicle’s operation, and you’ll want to have the car repaired promptly before the issue worsens.

3. P0401

The code P0401 means that there’s an issue with the exhaust gas recirculation. The description of this code is enough to make you question everything about this vehicle. But an EGR code means that there is an issue with the system that controls smog-causing nitrous oxides.

The vehicle’s exhaust system is connected to the EGR, which is responsible for recirculating the exhaust back into the engine cylinders.

Valves are opened and closed by your vehicle all of the time to help recirculate the exhaust back into the system. When a vehicle’s oil has not been changed for a long time and the vehicle is only used for very short trips, this may cause carbon to build up in the system and for the P0401 code to be presented.

The good news is that your mechanic may be able to clear your EGR valve which would make the repair much less expensive. But there’s also a chance that you’ll need to have the entire valve replaced. Tests can be performed by the mechanic which will try and diagnose exactly what’s wrong with your EGR valve.

Costs can range from $150 to $900 to replace the valve.

4. P0420, P0430

The P0420 and P0430 codes are very serious because it means that there is an issue with your vehicle’s catalytic converter. This converter is monitored by an oxygen sensor because the converter is responsible for key vehicle emissions.

The converter will convert the pollutants and toxic gases that your vehicle produces into less harmful substances.

A process called redox reaction takes place and this is when there is an oxidation and reduction reaction. The converter makes sure that the vehicle’s emissions are as clean as possible, although any form of emissions is not ideal.

The catalytic converter can be contaminated, and this is often a result of your engine’s oil leaking. You may also have a coolant leak that is causing the contamination of the converter. But there’s also a chance that the catalytic converter is now bad and needs to be fully replaced.

In either case, a mechanic should be consulted to determine what needs to be done to get your catalytic converter running smoothly again.

5. P0455, P0411, P0446, P0440, P0442

All of these codes point to another key issue that your vehicle has with the evaporation system.  The EVAP system is responsible for removing and containing all of the vapors that your engine produces when fuel is burned.

The combustion process has to produce these vapors in order for the vehicle to be propelled forward.

And while it sounds like an EVAP system issue would be a major repair, it’s one of the cheapest repairs available. The repair often includes replacing your gas cap which will start to crack and erode over time. When this happens, the vapors are no longer contained and the cap will need to be replaced.

You may also have a loose gas cap, and a simple twist or two of the cap is all that you’ll need to clear the code.

If you find that the cap is loose, you’ll want to tighten the cap and drive for 30 – 40 miles before you can expect the code to be cleared. But if you drive around for a few days and the code is still present, you can unplug the battery for 10 minutes to clear the code from the system. If the code comes back, you know that the issue is a little more than a mere gas cap.

November 17, 2019


There are no comments available.


What Makes InfinitiKloud So Unique?

Get your InfinitiKloud Today
Benjamin photo


Picture this: You’re driving down the highway, when all of a sudden your check engine light comes on. Your car had been driving a little funny, but nothing too out of the ordinary. In a panic, you pull over off the road and call a tow truck.

Read More