TPC Wire & Cable Blog

On-Board Diagnostic Trouble Codes For Automotive Technicians

Posted by TPC Team on December 6, 2018
TPC Team

on-board-diagnostics-2a-newRemember when you didn't need a computer science degree from the Massachusetts Institute of Technology (MIT) to actively diagnose automotive issues? If something was wrong, you just tinkered with the parts.

Sure, maybe we're over-exaggerating, but most new cars are, essentially, computers. They contain On-Board Diagnostics (OBD) systems that monitor the performance of major components and generate codes to indicate if something has gone awry.

Diagnostic Trouble Codes (DTCs) are how an OBD II Interface system pinpoints and transmits issues to automotive technicians, so it’s essential that technicians be able to understand the codes to quickly identify the problem
to minimize associated downtime.

How to Read DTC Codes
The first number in the DTC lets you know whether it is specific to the vehicle manufacturer or is an SAE generic code that applies to all OBD II systems. The last three numbers provide information regarding the specific vehicle circuit and system.

Here is an analysis of a typical OBD II code:


DTC Codes
Standard trouble codes start with P then a four-digit numeric code. Here are a few common vehicle error codes and what they signify:

DTC Codes P0100-P0199  Fuel and Air Metering

These codes are used to monitor the fuel and air ratio of the vehicle's engine to determine if an oxygen sensor is failing, plus they will monitor a vehicle's emissions and fuel economy. Here are some of the common codes within
this range:

  • P0135: O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)
  • P0141: O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)
  • P0171: System Too Lean (Bank 1)
  • P0174: System Too Lean (Bank 2) 

DTC Codes P0200-P0299 — Fuel and Air Metering (Injector Circuit)

These codes are going to involving fuel injectors. The most common codes within this range are:

  • P0200: Injector Circuit Malfunction
  • P0218: Transmission Over Temperature Condition

DTC Codes P0300-P0399 — Ignition System or Misfire

These codes will trigger if there are issues with the car's ignition. For example, if there are spark plug issues. The common codes within this range are:

  • 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
  • P0325: Knock Sensor 1 Circuit Malfunction (Bank 1 or Single Sensor)

Check out our On-Board Diagnostics Standard Trouble Codes list:

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DTC Codes P0400-P0499 — Auxiliary Emissions Controls

These codes will determine issues with the system's EVAP (evaporative emission control) systems. The EVAP's function is to prevent gas fumes to reach the atmosphere, thus keeping air pollution to a minimum. Some of the common codes in this range are:

  • P0401: Exhaust Gas Recirculation Flow Insufficient Detected
  • P0411: Secondary Air Injection System Incorrect Flow Detected
  • P0420: Catalyst System Efficiency Below Threshold (Bank 1)
  • P0430: Catalyst System Efficiency Below Threshold (Bank 2)
  • P0440: Evaporative Emission Control System Malfunction

DTC Codes P0500-P0599 — Vehicle Speed Controls and Idle Control System

These codes will monitor the vehicle's speed controls and idling. Issues from the Vehicle Speed Sensor (VSS) will trigger these codes. Here are the common codes found within this range:

  • P0500: Vehicle Speed Sensor Malfunction
  • P0505: Idle Control System Malfunction

DTC Codes P0600-P0699 — Computer Output Circuit

These codes will be triggered by a faulty computer system. The common codes found within this range are:

  • P0600: Serial Communication Link Malfunction
  • P0602: Control Module Programming Error
  • P0604: Internal Control Module RAM Error

DTC Codes P0700-P0899 — Transmission and Beyond

These codes monitor the system's transmissions. Most of the time, the code is triggered by a fault in the system's transmission computer. These are the common codes found within this range:

  • P0700: Transmission Control System Malfunction
  • P0702: Transmission Control System Electrical

Learn more about TPC's On-Board Diagnostics InterfaceIt's essential to have the proper tools to test
and diagnose a vehicle's on-board problem.

Accurate diagnosis is key to repair based on manufacturer suggestions. Being able to identify these codes will lead to decreased downtime and higher productivity.

Did you know that TPC Wire & Cable Corp. offers a vast selection of automotive wire, cord, and automotive cable accessories? Did you also know that we offer an OBD Interface?

Let's start the conversation today on how we can reduce your downtime and costs.

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Topics: Maintenance, Reducing Downtime, Products, Custom Cable, Automotive


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