You have just received your OBD scanner and are excited to start troubleshooting your own car, you plug in the reader and find all it is telling you is a code that is not easily reset and requires an investigation, this guide will go through the basic structure of how the code is formed, assist in decoding the 5 digit fault code and also some basic info on testing the faulty system.
I’m already assuming you have the basic electronic know how and are familiar with the inner workings of your machine. If not this might be a bit too technical so let me know in the comments if it is not clear. This article also continues on from our OBD tools article.
What does the car fault code mean?
It means the system has detected a problem in one of the onboard systems and is spitting out a code that relates to the specific section that has triggered the fault. Faults can come from any electronic system or sensor in your car so there are thousands of possibilities and all of them are converted into a simple 5 character fault code,
The 5 digits of the code
The 5 digit code is broken down into 4 sections, as outlined below.
1st digit
P = Powertrain
B = Body
C = Chasis
U = Undefined – most are communication or connection errors with the internal computer or between the scan tool and the computer.
2nd number
0 = Generic fault codes common in most vehicles
1= Brand specific fault code
3rd number
1-8 – Indicates the subsystem the code is from
4th and 5th number
0-99 – Indicates the specific area of the subsystem that triggerd the fault
Where can I get P1 or other fault codes?
Although there are a core set of universal codes the more specific faults are often unique to a certain make of car, in situations where the code is not common or in the software database there is a great database here . If they don’t have your car Google the code to find the exact meaning .
Don’t jump to conclusions
Always investigate as the code is not always so direct, for example if you have a fault code for the O2 sensor it does not always mean the sensor is faulty, it could be the wiring or the connection so be sure you test any part first. Often with sensors there is an acceptable resistance of the sensor, so grab Google or the shop manual and find the basic resistance test for the sensor, then check if it is matching to your sensor. If it is inspect the wiring all the way back to the ECU for continuity. This step is key as unless you test the circuit properly you could end up buying parts you don’t need.
What should I not attempt to fix myself?
After disconnecting the battery; most parts and connectors can be removed and tested without risk of damage however anything with a yellow wire connector usually indicates the safety and airbags system and that should not be plugged and unplugged. Any fault with the SRS airbags should be taken into a professional.
If you are after an OBD scan tool yourself please check out or range of scan tools.
I hope this has helped explain the codes and you now feel a bit more confident not only accessing the codes but also hunting and fixing the problem.
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