What are Diagnostic Trouble Codes?
As you can imagine, modern vehicles that are laden with various electronic systems , are highly
complex, and that can
make it difficult to identify and locate a fault when one happens. Diagnostic Trouble Codes (DTCs), are used by the
vehicle’s on-board diagnostics (OBD) system to provide
information about what and where a problem is occurring.
The codes are triggered by individual systems when they encounter a fault that cannot be self-fixed, with the OBD
System generating the appropriate code and storing it for retrieval by technicians.
How to Read DTC Codes
Each diagnostic trouble code includes five characters, but the good news is that they are fairly straightforward,
and it is relatively easy to understand what a DTC means when generated.
The first character in the code is a letter that indicates the general location of the issue, these are:
The second character is a number that tells you the type of code it is:
The third character tells us which subsystem the problem is affecting and ranges from 1 to 8 in value.
The final two characters tell us the specific problem being reported.
In practice, you would see a DTC reported as something like P0302. Here, P tells us it a powertrain problem, 0 means
a generic code, with 3 informing us it is an ignition system or misfire problem. Finally, 02 indicates an issue with
cylinder 2, so putting it all together, and we have a misfire issue in cylinder number 2.
Automotive Diagnostic Trouble Codes
Because vehicles are so complex these days, DTCs generated by the vehicle’s
on-board computer are essential for
identifying problems, and are a significant help in speeding up fault finding and maintenance. They are so essential
in modern vehicle maintenance, that any technician, or vehicle owner, really does need to understand how to read
them to be able to maintain their vehicles.
We discussed the first letter as identifying where the problem is, but what do they mean? Powertrain issues relate
to the engine, transmission and related components, or the electric equivalents. Body faults will include things
like airbags, seats, air conditioning and so on, while chassis
faults are key systems such as braking, suspension
and so on. Unidentified faults relate to network and vehicle integration problems in the vehicle.
In a similar way, each code for faults has a specific meaning, and you can quickly look these up in manuals for both
generic and manufacturer specific issues, you don’t have to learn them all. But the question you probably have, is
how do you get the codes, right?
We use a diagnostic scanner tool, which connects to the vehicle’s OBD-II port , usually situated under the dashboard
somewhere. The canner can read out all the generated diagnostic trouble codes in the vehicle, and then clear them
once you have fixed the issue. This also turns off associated warning lights such as engine check and so on, that
are automatically activated when a code is generated. See our tips to handle check
engine lights .
It is good practice to check if any codes are active on a vehicle fairly regularly, as it can often be easier and
cheaper to fix it in those early stages before it develops into a more serious issue.
The Importance of DTCs
DTCs are an early warning signal for issues with a vehicle, highlighting that a system has detected a fault that
needs addressing. If left too long, these issues develop into more serious problems, costing more time and money to
remedy.
OBD2 Scanner – Your Tool for Reading DTCs
The key tool for dealing with DTCs is the OBD2 Scanner , an
electronic device that plugs directly into your vehicle’s
OBD-II port. It can read and clear codes it finds stored in the vehicle’s memory, helping to identify and fix
issues.
For instance, if you plug in an OBD2 scanner and it displays code P0171, you can look up the codes in a DTC list,
and know that it is telling you the engine is running lean. You can then take a closer look at the oxygen sensor, or
for a vacuum leak, to remedy the issue.
Conclusion
Like any code system, from the outside DTCs can seem complex, but with a basic understanding of how to read the
codes, a scanner and a DTC list, you can quickly identify problems with your vehicle. As a key part of a
comprehensive maintenance program, DTCs can keep your vehicle running better for longer, avoid expensive problems
and get the most from any vehicle.
Cloud Login
