We are Jimmy & Leigh-Ann here to offer some monthly tips, tricks and tales from the automotive industry. Weather you are fellow gearheads, garage aficionados, or maybe you think about blinker fluid (Hint, Hint, you don’t have any blinker fluid), we are here for you.

When you have a light come on your dash, it’s your vehicle’s way of saying something needs attention. It could be urgent or it could be a reminder for upcoming needs. The light is related to a code and that code acts as an area code for what system to look at and what various components you should be testing to verify a fault. Its not always simple with sensors, connectors, wiring and mechanical components that all need to be assessed, but its worth investing in proper diagnostics

than shooting off a parts cannon and crossing your fingers.

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Codes usually look something like “P0301” “P0700” or “C1234.”

1. First Letter: The System

The first letter tells you which system is affected.

  • P – Powertrain: This covers the engine, transmission, and fuel systems (e.g., “P0301” could mean an engine misfire).
  • B – Body: These codes relate to things in the car body, like airbags, seats, and seatbelts.
  • C – Chassis: This covers systems that help the car move, like the suspension, steering, and brakes.
  • U – Network & Undefined: This is related to communication codes between different systems in the car or any undefined issues.

2. First Digit After the Letter: General or Manufacturer-Specific

  • 0 – Standard/Generic
  • 1 – Manufacturer-Specific

3. Second Digit: Specific Sub-System

This number narrows down the system that is affected. Here’s how it works:

  • For Powertrain (P) codes, the second digit specifies the area of the system:
    • 1 – Fuel and Air Metering
    • 2 – Fuel and Air Metering (specific to injector circuit)
    • 3 – Ignition System or Misfire
    • 4 – Auxiliary Emission Controls
    • 5 – Vehicle Speed Control and Idle Control Systemo
    • 6 – Computer Output Circuit
    • 7, 8 – Transmission

4. Last Two Digits: Affected Area Within The System

The last two numbers target a specific component(s)

For example:

  • P0301:
    • P – Powertrain
    • 0 – Generic code
    • 3 – Ignition System or Misfire
    • 01 – Cylinder 1 misfire

So, P0301 would mean that the car’s computer has detected a misfire in Cylinder 1. In order to find the root cause of that misfire, a host of things would need to be checked: wiring, connectors, vacuum leak(s), cylinder compression, plugs, coils, injectors … When you have thousands of integrated parts on each vehicle having a code to work off of is actually a good thing when troubles arise.

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