How to Use OBD2 Scanner

Has your Check Engine Light (CEL) come on and you have no idea why? The OBD2 is a state-of-the-art diagnostic computer system that tells you why and when your automobile has trouble. Computers in cars? It all started with electronic fuel injection (EFI) and a strong desire for greater automotive emissions control. Sure, the OBD1 was a great technological disruption, paving the way for the main automotive self-check applications that we use today.

Yet, it was designed before all of the wonderful signaling technology we have now. The OBD1 was limited, unstandardized, and differentiated across automotive manufacturers in many ways. The OBD2 is the follow up monitor to the OBD1, gathering data from vehicles manufactured after 1996 with a simplified design. The OBD2 expanded the diagnostic and monitoring vision well beyond exhaust emissions.

OBD2 Scanner Features

Don’t confuse the OBD2 Scanner (view on Amazon) with the OBD2 Reader. The OBD2 Scanner is a standardized, handheld tool used to interpret the data gathered by the monitor. Some of the useful diagnostic information made available by the OBD2 includes rpm, coolant, road speed, and air temperature information.

The OBD2 Scanner is a bit more sophisticated than the OBD2 Reader. The Scanner can read more complex manufacturer codes, shut down the MIL or CEL, and can conduct advanced troubleshooting. Some Scanners can set up pids, check on pending codes, generated parameter lists, and provide more detailed information. The more features the OBD2 Scanner has, the more it costs. Make sure you purchase an OBD2 Scanner that is compatible with the OBD tool that is installed on your car. Also, choose a Scanner that has a user-friendly interface.

How the OBD2 Scanner Works

You may say “I have lights on my dash that let me know if something is going wrong”. Well yes, that’s truth. However, there are only so many lights on the dash compared to how many things that can go wrong with your car? The OBD2 Scanner responds to thousands of codes that trigger the malfunction indicator light (MIL) or Check Engine Light (CEL) on the dashboard. When the MIL or CEL activates, it means that sensor in some part of the automobile is sending an error message to the powertrain control module (PCM). The PCM actually activates the warning light and stores a trouble code for the problem.

How to Use the OBD2 Scanner

Once you have the OBD2 Scanner, read the manual for your scanner model and become acquainted with its features. The manual may also come with a CD-ROM copy that is easier to understand. Also, your vehicle should be equipped with an OBD2 connector (view on Amazon). Look for the connector under your dash, on the left side of the steering wheel. The connector will be either rectangular or shaped like a trapezoid with 16 pins split into two rows of 8. More recently, the OBD2 has become available using ‘Dongles’, automatic OBD2 plugs that connect with the application through a wireless network.

Ok, you’ve got your Scanner, you’ve read the manual, and located the connector. Now, it’s time for you to use it. The device does not require any excessive mechanical prowess. Just follow these steps to use your OBD2 Scanner:

1. Before connecting the OBD2 Scanner, turn your automobile engine OFF. Then, very gently plug the scanner in to the OBD2 data link connector (DLC) under the driver’s side dashboard. The cable should be under the left side of the steering wheel. Plug the Scanner into the 16 pin plug.

2. Once the Scanner is plugged into the dash, turn the ignition switch ON, or run the engine (check your manual to determine which one fits your car). Once the ignition is ON, or the car is running, turn your Scanner ON, and give it a little time to initialize. There will be options for you to ‘View Data’.

3. Once your Scanner is hooked up, it will prompt you for information, such as the VIN number and type of engine. Now that your Scanner is connected to your vehicle and up and running, you can key in the data about your vehicle. After you have entered the vehicle information, initiate a scan of the system based upon the manual for your Scanner type.

4. The Scanning process could take an indefinite amount of time. Once the scan is complete, you should see one or several trouble codes on the screen. Record or transfer the codes by hand or by USB to your computer. (if you don’t see any codes, then your vehicle may not have any of the problems detectable by the OBD2).

5. Check your codes against the diagnostic trouble codes (DTCs) list to verify what they are telling you about your car. Then check the issues with your owner’s manual to understand what they mean and what the manufacturer suggests. You can also check the codes online.

6. When you finish retrieving your DTCs, reset the MIL for inspection and readiness (I/M readiness)

Interpret the Diagnostic Trouble Codes (DTCs)

Once the Scanner has done its work, you should have received one or more DTCs for your vehicle. The DTCs are the highlight of the OBD standardization. The primary objective was for the Scanner to identify emissions problems from the exhaust and to add an electronic unit to support the EFI. However, the OBD3 Scanner will pick up many other malfunctions. Once the scan is performed, you may receive one or several trouble codes, and now it’s time to figure out what it all means.

As with everything else, the OBD codes became more detailed in the OBD2 framework. The double digit codes for the OBD1 have changed to identify the issues more specifically. There are more than 5,000 OBD2 DTCs, some generic, some by the automobile manufacturer.

The generic codes is defined by EOBD/OBD2 standard and is universal across all manufacturers.

These codes usually begin with ‘P0…’. The manufacturer codes is created by the vehicle manufacturer and are unique to each brand. The manufacturer code commonly will begin with ‘P1…’.

The DTC is a string of five characters. The code may be ‘P0128’. The first letter in the DTC stands for one of the four main body parts: P = Powertrain, or ‘P0…’; N = Network, or ‘U0…’; B = Body, or ‘B1, B2, B3…’; and C = Chassis, or ‘C1, C2, C3…’. This is the first clue of what the problem is in your vehicle.

The second character is a ‘0’ or a ‘1’. A ‘0’ is the generic code. Also remember, a ‘1’ means the DTC was created by the vehicle manufacturer.

The third character can be numbers or letters and each represents a part of the automotive system. For example, the letter A, B, or C refers to ‘hybrid propulsion’. A ‘1’ means ‘fuel and air metering’. A 2 = ‘ fuel and air injector circuit’. A ‘3’ = the ignition. A ‘4’ = ‘auxiliary emission control’. A ‘5’ = ‘vehicle speed and idle control systems’. The numbers 7-9 are related to the transmission.

The fourth and fifth characters describe the problem for the indicated area. The numbers are coupled, such as “00” or “02”. Each of these parts is only a partial explanation of the issue with your car. The DTC should be taken collectively, a combination of all of the information along with the information in your owner’s manual. If you are not sure what the code means, ask a certified professional.

Below is a list of some of the most common OBD2 troubles and what they mean:

OBD2 Trouble Codes
Code Issue
P0128 Coolant Thermostat (Coolant Temp. below Thermostat)
P0171 System Too Lean
P0174 System to Lean
P0300 Random/Multiple Cylinder Misfire Detected
P0401 Exhaust Gas Recirculation “A” Flow Insufficient Detected
P0420 Catalyst System Efficiency Below Threshold
P0440 Evaporative Emission System
P0442 Evaporative Emission System Leak Detected (small leak)
PO455 Evaporative Emission System Leak Detected (large leak)
B0028 Right Front Passenger Side Deployment Loop Resistance Low
B1216 Emergency & Roadside Assistance Switch Circuit Short to Ground
B1232 See Manufacturer
B1248 Passenger’s Seatback Autoglide Rearward Switch Circuit Short to Ground
B1292 Battery Power Relay Circuit Failure
B1307 Oil Level Switch Circuit  Short to Battery
B1367 Ignition Tach Circuit Failure
C1091 Speed Wheel Sensor All Coherency Failure
C1097 ABS Hydraulic Pump Motor Circuit Short to Ground
C1229 Speed Wheel Sensor Rear Center Coherency Fault
C1895 Air Suspension LR Height Sensor Circuit Short To Battery
C1907 Ride Control LR Shock Actuator Circuit Short To Battery
C1932 Air Suspension Front Compressor Relay Circuit Short To Ground
U0001 High Speed CAN Communication Bus
U0105 Lost Communication With Glow Plug Control Module
U0115 Lost Communication With ECM/PCM “B”
U0120 Lost Communication With Starter / Generator Control Module
U0154 Lost Communication With Restraints Occupant Sensing Control Module
U0181 Lost Communication With Headlamp Leveling Control Module

Most every automobile manufacturer observes the OBD2 standard. They may use the OBD2 along with data loggers to track the automotive systems. As you can see, the trouble code letters and numbers for OBD2 correspond with one of the four major parts of the vehicle. There are so many possibilities for any one part within a system. You really must understand what the DTC codes mean as well as what they could mean.

Why You Have OBD1 Codes in the First Place

The main reason why you have codes to diagnose in the first place is because there’s a problem in your vehicle and this has sent a signal to the diagnostics unit and the problem has been stored as an error. The most common reason why people have problems with their cars is that they fail to maintain it. Maintenance is a compulsory thing that needs to be carried out by every car owner and if not done, certain components will fail and this will be expensive to repair at the dealership.

If you want to avoid problems or other issues and save $100s of dollars that you’ll spend at the dealership, you’ll need to service your vehicle often – you can use our mechanic-rated Auto Maintenance and Repair Manual to do this. It’s basically what mechanics use to go through your vehicle to check if there are any problems that need fixing. As soon as they notice the most minor problem, they’ll ask you to fork out some money even though it’s a problem you can fix yourself in a few minutes – the manual will teach you how to maintain your vehicle every few thousand miles and it’ll teach you how to fix minor problems that mechanics will ask you to pay for; saving you money in the long run.

A lot of our readers have this maintenance manual printed on their garage walls and a lot of them haven’t visited the mechanic in a few years because they know what to do to avoid problems. All it takes is giving your vehicle a little attention every few thousand miles and you’ll never spend money at the dealership again.

Relying on Diagnostic Trouble Codes (DTCs)

Technology has evolved and made for some really useful tools in the automotive fields. We knew that computers were coming to our dashboards and under our hoods and we were right. The computers are here! Now, every vehicle owner should own an OBD2 Scanner so that you can have an edge on maintaining the health of your car. The price of the Scanner has become reasonable as so many people now use them. However, not many things are infallible so the OBD2 Scanner should not be your only source of support. Your vehicle comes with a manual that provides specialized insight into how your vehicle runs and what it needs.

Also, just because you have pinpointed a problem in your automobile, that doesn’t mean you know to fix it. For example, a DTC could report that a certain part is malfunctioning; however, the malfunction may be because of another part that is not associated with the code. When following up with the trouble codes, be sure to consult with your owner’s manual as well as a trusted technician before you act on the problem.

OBD2 Scanner Expert

The basics of choosing an OBD2 Scanner and DTCs were covered in this article. So now you know all there is to know about the OBD2 Scanner, including how to use it. You’re an expert now on OBD2 Scanners and DTC code! Well done!