DTC Codes: What They Are and How to Read Them

Most drivers, when a warning light comes on in their vehicle’s dashboard, wonder what’s going on. The answer often lies in a crucial yet sometimes mysterious system: the On-Board Diagnostics (OBD).

When a vehicle’s OBD system detects an issue, it generates a code that helps technicians identify the source of the malfunction. These are known as DTCs (Diagnostic Trouble Codes).

In today’s blog from Sun Transmission, we’ll explain what these codes are, how to read them, and why they’re essential for diagnosing vehicle problems.

What is a DTC?

A DTC is an alphanumeric code generated by the onboard diagnostics system when it detects a fault or anomaly in a vehicle component. The OBD-II system, which is present in most vehicles manufactured after 1996, can detect issues in systems such as the engine, transmission, brakes, and other components critical to the car’s performance and safety.

Components of a DTC

A DTC consists of a series of characters that provide specific details about the detected fault. The codes follow a standardized format, typically seen as:

P0123. The first letter of the code indicates the fault category:

• P: Powertrain issues (engine and transmission).
• B: Body system issues.
• C: Chassis issues.
• U: Vehicle communication network issues.
  

The two-digit number (01-99) that follows helps identify the specific area of the vehicle with the issue. For example, P01xx relates to the fuel system, while P03xx may indicate an ignition system problem.

The last three digits (xxx) provide more specific details about the fault. For instance, P0123 could indicate a problem with the throttle position sensor, while P0456 refers to a small leak in the fuel evaporation system.

How to Read a DTC

Reading a DTC might seem complicated at first, but it’s not as difficult once you understand its structure. To read these codes, you’ll need an OBD-II scanning tool, which can be a portable scanner or a mobile app. These tools allow you to read the codes stored by the system and often provide a description of what each code means.

Here’s a quick guide to using the scanner:

• Connect the OBD-II scanner. The first step is to locate the OBD-II port in your vehicle, usually found under the dashboard, near the pedals. Connect the scanner to the port.
• Read the DTC. The scanner will display a series of DTCs corresponding to any issues detected by the OBD-II system.
• Interpret the code. Once you have the code, consult the vehicle’s manual or use a DTC code database to identify which part of the system is malfunctioning.
• Diagnosis and repair. With the code and its description, the technician can diagnose the affected area and determine if a specific part needs repair or replacement.
  

DTC Codes in Automatic Transmissions

Automatic transmissions are a key component in vehicle operation, and DTCs are essential for diagnosing issues in them. Automatic transmissions are controlled by a series of sensors and actuators that manage the shifting speed and the precision of power transmission.

When there’s a problem in the transmission system, a DTC can pinpoint the failure area.

For example, P0700 and P0710 are common in automatic transmissions and typically indicate issues with the transmission temperature sensor or the transmission range switch.

By reading these codes with an OBD scanner, a mechanic can determine if the issue is related to the speed sensor, shift solenoid, or the transmission control module.

The Importance of Identifying and Understanding DTCs

Recognizing and understanding DTCs is crucial for accurately diagnosing the vehicle’s issue and pinpointing the affected area. Correctly identifying the code helps technicians focus on the specific area that needs attention, avoiding incorrect or unnecessary diagnoses. Moreover, it can save you time and money by preventing costly repairs that don’t address the root cause of the problem.

Find Automatic Transmission Parts at Sun Transmission

Now that you know more about DTC codes, if you’re in need of parts for automatic transmissions or hydraulic steering, visit our online store to find high-quality products for a wide range of makes and models. Shop now at Sun Transmissions and ensure your vehicle runs at its best!