There comes a day in the life of every vehicle owner when something will inevitably go wrong. What do you do when your car is on the fritz? Well, before you take it to the mechanic, you’ll probably inspect the vehicle to see if you can identify the problem.
Keep reading to learn about how vehicle diagnostics work, the function of your on-board diagnostics system, plus common on-board vehicle diagnostics errors, and how to fix them.
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- 1 What Are On-Board Vehicle Diagnostics and How Do They Work?
- 2 What Is the Function of a Vehicle’s On-board Diagnostics System?
- 3 Standard Obd2 Error Codes and How to Fix Them
- 4 Wrapping It Up
What Are On-Board Vehicle Diagnostics and How Do They Work?
In any passenger car or another automotive, the machine’s vehicle diagnostics are a highly complex and essential process to the function of the vehicle. Diagnostics parameters adjust based on whether or not the car is in motion are at rest in the garage. Off-board and on-board vehicle diagnostics exist to account for both sets of circumstances.
For this article, we’ll focus solely on on-board vehicle diagnostics. Standard vehicle diagnostics components check the operations performed by the machine’s sensors, subsystems, and other elements. When these components discover any errors, they record the issue in the vehicle’s error memory in the form of Diagnostic Trouble Codes (DTCs).
On-board vehicle diagnostics focus primarily on emission protocols and diagnosis.
What Is the Function of a Vehicle’s On-board Diagnostics System?
In simple terms, on-board vehicle diagnostics or OBD2 are relevant when your vehicle is in motion. The machine conducts these tests while your car is on the road, and you can see the results on your car’s dashboard.
On-board vehicle diagnostics results show in the form of your vehicle’s malfunction indicator light (MIL) or an on-board vehicle diagnostics testing tool.
All on-board diagnostics data relates to engine and transmission electronic control units and the emission control system. All vehicles manufactured in the U.S. after 1996 were required to feature on-board diagnostics to keep car emissions levels in check.
Your car’s on-board diagnostics system checks every aspect of vehicle emissions from fuel injectors to oxygen sensors. In the event of a malfunction, the malfunction indicator light will go off to warn you that there’s a problem. Certain high-end vehicles may also feature a limp home mode that allows you to drive back home or to the mechanic without increasing the damage to your machine.
The error that stimulates the malfunction indicator light is in the automotive electronic control unit which the mechanic can retrieve later with the tester tool. The interesting aspect about on-board diagnostics is these the system contains services that are not unique to a specific type of vehicle or model.
A professional mechanic can access your on-board vehicle diagnostics codes to measure the health of your vehicle’s engine. However, you can also retrieve these codes at home, provided you have the right tools.
By connecting a scan tool into the computer-like port on your vehicle, you can download the codes and identify the source of any malfunction. Be sure to check your repair manual to determine the port’s location.
Many auto parts chain retailers will scan your on-board vehicle diagnostics codes for free. You can also visit an on-board vehicle diagnostics code website that translates each code into layman’s terms.
Standard Obd2 Error Codes and How to Fix Them
There are four different categories of diagnostic codes: Powertrain (P), Body (B), Chassis ©, and Network Communications (U). These codes are subdivided into global or generic codes with 0 as the digit and manufacturer-specific or enhanced codes with 1 as the second digit.
When your malfunction indicator light goes off, the following are the most common diagnostic codes you will probably see during your driving life:
- Codes PO171 – P0175
- Codes P0300 – P0305
- Code P0401
- Codes P0411, P0440 P0442, P0446, and P0455
- Codes P0420 and P0430
Let’s delve into what each of these codes means for your vehicle and what you can do about them.
Codes PO171 – P0175: The Oxygen Sensor
Oxygen sensor malfunctions are a common vehicle issue. Your car’s oxygen sensor moderates the level of oxygen present in the exhaust so the engine’s computer can tweak the fuel mixture as needed. These adjustments not only increase fuel economy but cut back emissions.
When your oxygen sensor isn’t functioning correctly, you’ll notice your gas mileage increasing. Sometimes, the car will stall.
If your oxygen sensor fails, you could order an OEM or aftermarket replacement part online from a reputable vendor or wholesaler. Once you receive the part in the mail, you can use one or two oxygen sensor sockets or automotive wrenches to get the job done. Always check your vehicle’s manual for exact directions.
Codes P0300 – P0305: Engine Misfire
When your engine misfires, this means that either one or multiple cylinders aren’t functioning as they should. If your car vibrates when you idle it and your vehicle isn’t using fuel as efficiently as it used to, you could be dealing with an engine misfire.
The on-board vehicle diagnostics system monitors engine misfires by checking crankshaft speeds when you run the engine. The system records a misfire if it identifies even a mild speed loss in the crankshaft.
You should never ignore a misfire, as the issue can cost considerable time and money to uncover. If the misfire is due to faulty spark plugs, these are cost-effective and typically quick to switch out. Spark plugs usually have an 80,000 to 100,000-mile service life. If you switch out the spark plugs, it might not be a bad idea to check the spark plug wires and see if they need a replacement.
The ignition coil and vacuum leaks are also potential causes for an engine misfire. If you have the time and tools, you could replace these at home if necessary with relative ease.
Code P0401: EGR or Exhaust Gas Recirculation
Also known as EGR, the exhaust gas recirculation controls your car engine’s emission of nitrous oxides that cause smog. EGR recycles a portion of the machine’s exhaust gas and filters it back into the engine’s cylinders. The vehicle computer opens and shuts the values to recover the exhaust gas.
If you don’t change the oil regularly or if you take your vehicle on numerous short excursions without warming it up properly, this can cause carbon stores. You can try cleaning the EGR valve at home with carbon cleaner and reinstall before jumping to replace the whole thing. If cleaning and reinstalling the EGR doesn’t work though, you may need to replace the entire component.
Codes P0411, P0440 P0442, P0446, and P0455: The Evaporative System
Your vehicle’s evaporation system of EVAP is tasked with holding and removing vapors created when burning fuel. If the gas cap is loose and allows fuel vapors to emit, this can trigger the error code. The EVAP encompasses the purge valve, vent hoses, charcoal canister, and vacuum sensor or pressure valve.
When your car triggers an EVAP error code, the first step you can take to try to fix the issue would be to re-install the fuel cap. If you think the fuel cap could be bad, you may opt to replace it entirely. You could also check to see if you notice loose or damaged houses beneath your car hood, as this could also trigger this type of code.
If none of these steps suffice to resolve the issue, you may wish to consider taking your vehicle to a repair shop to be checked by a licensed mechanic. The repair shop would have a smoke machine that can filter smoke through the entire EVAP and pinpoint the source of the leak.
Codes P0420 and P0430: The Catalytic Converter
Your vehicle’s downstream oxygen sensor regulates the catalytic convertor. The catalytic converter is an emissions control component that transforms gas pollutants and other toxins in exhaust gas to less toxic substances. The catalytic convertor enacts a reduction and oxidation process that converts the contaminants.
Over time, the convertor can contaminate and promote tailpipe emissions if the engine is leaking coolant or burning oil. Sometimes, the convertor wears out from age.
You can sometimes unclog a catalytic converter by driving your vehicle on the highway for one or two miles. Find a place where you can cut back your speeds quickly, push your breaks, and repeat. If you notice an increase in performance, you’ve just unclogged the catalytic converter.
If issues continue, speak with your mechanic so they can dismantle the catalytic converter to see if it needs to be unclogged or changed out completely.
Wrapping It Up
We hope you have a better understanding of the primary on-board vehicle diagnostics error codes, what they mean, and what to do if your system triggers an error message. If you can identify the problem, you are one step closer to reaching a solution.
It doesn’t matter if you’ve owned many vehicles in your driving life or are the proud owner of your first car. Understanding how to perform a necessary inspection of your machine could save you time, expense, and trouble in the long run.
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