Understanding DTC Codes

DTC codes are Diagnostic Trouble Codes. They are used by mechanics to help diagnose issues with a vehicle. The code is a series of letters and numbers that identify the issue. This is stored in the vehicle's computer and can be accessed with a code reader.

DTC codes can be tricky to decode, but there are a few resources that can help. One is the website obd-codes.com. This site has a database of codes and their meanings. Another resource is your vehicle's owner's manual. If you are already partnered with MiX by Powerfleet for your fleet, you may already have the ability to read DTC codes that are uploaded directly to your telematics platform, saving you time, money, and the hassle of running a scan using an OBD-II reader.

If you think you may have a DTC code, possibly indicated by a Malfunction Indicator Lamp on the fleet vehicle's dashboard, the best course of action is to take the fleet vehicle to your service technician. They will be able to help you determine the cause of the code and fix the problem.

The Origin of DTC Codes

DTC codes were first introduced in the early 1980s and were originally only used internally by manufacturers to identify issues with a vehicle. In 1996, there was a movement led by the Society of Automotive Engineers to standardize these codes across manufacturers so that they could be read by any scanner. This allowed outside mechanics and service technicians to quickly identify issues with a vehicle, regardless of the make or model.

Due to this standardization, these codes can be accessed with a handheld code reader or through a fleet management platform like MiX by Powerfleet.

Breaking Down a DTC Code

The structure of a DTC code can help you understand a lot about the issue and what part of the vehicle is being impacted.

Each code is comprised of a letter: P, B, C, or U, followed by a four-digit code starting with either a 0 or a one, and three digits for the specific problem.

P stands for Powertrain, B stands for Body, C stands for Chassis, and U stands for Network. The first number is either 0 for a generic code or 1 for a manufacturer-specific code.

Common DTC Codes

The DTC codes you are most likely to see in your fleet vehicles are:

P0100 - Mass or Volume Air Flow (MAF) Circuit Malfunction

P0101 - Mass or Volume Air Flow (MAF) Circuit Range/Performance Problem

P0102 - Mass or Volume Air Flow (MAF) Circuit Low Input

P0103 - Mass or Volume Air Flow (MAF) Circuit High Input

P0104 - Mass or Volume Air Flow (MAF) Circuit Intermittent

P0106 - Manifold Absolute Pressure/Barometric Pressure Circuit Malfunction

P0107 - Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem

P0113 - Intake Air Temperature Circuit High Input Bank 1

P0118 - Engine Coolant Temperature Sensor Circuit 1 High Input

P0121 - Throttle Position Sensor/Switch A Circuit Range/Performance Problem

P0122 - Throttle Position Sensor/Switch A Circuit Low Input

P0123 - Throttle Position Sensor/Switch A Circuit High Input

P0125 - Insufficient Coolant Temperature for Closed Loop Fuel Control

P0128 - Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

P0130 - O2 Sensor Circuit Malfunction (Bank I Sensor 1)

P0131 - O2 Sensor Circuit Low Voltage (Bank I Sensor I)

P0132 - O2 Sensor Circuit High Voltage (Bank I Sensor 1)

P0133 - O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)

P0135 - O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)

P0136 - O2 Sensor Circuit Malfunction (Bank I Sensor 2)

P0137 - O2 Sensor Circuit Low Voltage (Bank I Sensor 2)

P0138 - O2 Sensor Circuit High Voltage (Bank I Sensor 2)

P0139 - O2 Sensor Circuit Slow Response (Bank 1 Sensor 2)

P0140 - O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 2)

P0141 - O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)

P0150 - O2 Sensor Circuit Malfunction (Bank 2 Sensor 1)

P0151 - O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)

P0153 - O2 Sensor Circuit Slow Response (Bank 2 Sensor 1)

P0155 - O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)

P0159 - O2 Sensor Circuit Slow Response (Bank 2 Sensor 2)

P0161 - O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 2)

P0171 - System too Lean (Bank 1)

P0172 - System too Rich (Bank 1)

P0174 - System too Lean (Bank 2)

P0175 System too Rich (Bank 2)

P0300 - Random/Multiple Cylinder Misfire Detected

P0301 - Cylinder 1 Misfire Detected

P0302 - Cylinder 2 Misfire Detected

P0303 - Cylinder 3 Misfire Detected

P0304 - Cylinder 4 Misfire Detected

P0305 - Cylinder 5 Misfire Detected

P0306 - Cylinder 6 Misfire Detected

P0307 - Cylinder 7 Misfire Detected

P0308 - Cylinder 8 Misfire Detected

P0309 - Cylinder 9 Misfire Detected

P0310 - Cylinder 10 Misfire Detected

P0311 - Cylinder 11 Misfire Detected

P0312 - Cylinder 12 Misfire Detected

P0325 - Knock Sensor 1 Circuit Malfunction (Bank 1 or Single Sensor)

P0340 - Camshaft Position Sensor Circuit Malfunction (Bank 1)

P0341 - Camshaft Position Sensor Circuit Range/Performance (Bank 1)

P0400 - Exhaust Gas Recirculation Flow Malfunction

P0401 - Exhaust Gas Recirculation Flow Insufficient Detected

P0402 - Exhaust Gas Recirculation Flow Excessive Detected

P0403 - Exhaust Gas Recirculation Circuit Malfunction

P0410 - Secondary Air Injection System Malfunction

P0420 - Catalyst System Efficiency Below Threshold

P0421 - Warm Up Catalyst Efficiency Below Threshold

P0430 - Catalyst System Efficiency Below Threshold

P0431 - Warm Up Catalyst Efficiency Below Threshold

P0440 - Evaporative Emission Control System Malfunction

P0441 - Evaporative Emission Control System Incorrect Purge Flow

P0442 - Evaporative Emission Control System Leak Detected (small leak)

P0443 - Evaporative Emission Control System Purge Control Valve Circuit

P0455 - Evaporative Emission Control System Leak Detected (gross leak)

P0456 - Evaporative Emissions System Small Leak Detected

P0500 - Vehicle Speed Sensor "A" Malfunction

P0601 - Internal Control Module Memory Check Sum Error

These are just the most common codes. If you see any of these codes in your fleet vehicles, be sure to take them to your service technician as soon as possible to avoid further damage.

There are many other DTC codes that indicate a variety of issues with different parts of the vehicle. To get a full list of DTC codes and their meanings, visit obd-codes.com or visit your fleet service technician to get a full diagnostic report.

Determining If Your Fleet Vehicles Are OBD-II or J1939 Compliant

If you want to read DTC codes from your fleet vehicles, you need to make sure they are OBD-II compliant. Most vehicles manufactured after 1996 are compliant. However, some commercial vehicles, such as trucks and buses, may be J1939 compliant. This means they use a different system to communicate data, and you will need a different type of scanner to read their codes.

To determine if your vehicle is OBD-II compliant, you can do a quick Google search for your make and model followed by "OBD-II compliant." If you are still unsure, you can always take your vehicle to your service technician, and they will be able to tell you for sure.

Once you have determined that your vehicle is OBD-II compliant, you can purchase an OBD-II reader. These are relatively inexpensive and can be found at most auto parts stores. If your fleet is J1939 compliant, you will need to purchase a heavy-duty scanner that is specifically designed for that system.

Once you have your OBD-II reader, you can connect it to your vehicle and read the codes. The reader will have a specific set of instructions on how to do this, so be sure to follow them carefully.

How to Read DTC Codes

If you have determined that your fleet vehicle is OBD2 compliant and you have an OBD-II reader, follow these steps to read the codes from your vehicle:

1. Plug the OBD-II reader into the diagnostic port under the dashboard.
2. Turn on the ignition, but do not start the engine.
3. The reader will scan and then display any codes that are stored on the vehicle's computer.
4. Write down the codes, and then look up their meanings so you can determine what is causing the problem.
5. Take your vehicle to a service technician, and show them the codes so they can help you fix the problem.

If you don't have an OBD-II reader, you can take your vehicle to a service technician, and they can use their own scanner to read the codes for you. Many popular auto parts stores will allow customers to borrow a scanner to use in the parking lot or will offer one as a rental if you are unable to drive your vehicle to the location safely.

DTC Tools for Fleet Managers

If you manage a fleet of vehicles, it is important to have the right tools to help you maintain them. This includes having a way to quickly and easily read DTC codes.

There are a few different options available for fleet managers when it comes to DTC tools. The first is to purchase your own scanners. This is a good option if you have the budget for it, and it can be a helpful additional piece of data to add to your vehicle inspection reports.

If you are using a telematics platform, you may be able to get DTC code notifications directly to your fleet's telematics dashboard, eliminating the need for a separate scanner altogether. This can be a more cost-effective option and can help you keep track of all the data in one place. You also won't need to rely on your drivers to self-report these issues in the vehicles they are operating or wait until the next routine inspection of the problematic fleet vehicle.

Contact MiX by Powerfleet To Discuss Your Fleet Management Needs

Contact us today if you would like to learn more about how MiX by Powerfleet can help you manage your fleet and stay on top of your fleet's DTC codes. Our team of experts would be happy to discuss your specific needs and help you find the right solution for your business.