How to read a check engine code with an OBD2 scanner

Teach: How to read a check engine code with an OBD2 scanner

What to say

To read a check engine code, plug an inexpensive diagnostic scanner into the port under the dashboard on the driver's side, switch the ignition on, and let it read the stored codes, which look like P0420. Write each code down and look up what it means. A code points to a system, not a finished diagnosis, so use it to ask the garage better questions.

What to show, in order

1. Find the diagnostic port: a 16-pin socket under the dashboard on the driver's side, near your knees; the manual shows where.
2. With the engine off, push the scanner's plug firmly into the port.
3. Turn the ignition to on, or start the engine if the scanner's instructions say so.
4. Choose read codes, and write down every code exactly, including the letter and all four digits.
5. Note whether each code is stored, pending or permanent, and take a photo of any freeze frame data the scanner shows.
6. Look up each code's general meaning, then treat it as a starting point for a check, not a list of parts to buy.
7. Leave the codes stored and give the list to the garage; clearing them erases information a technician uses.

When to stop and call a professional

• The check engine light is flashing, or the car shakes, loses power or smells of fuel.
• Codes relate to brakes, airbags, steering or the hybrid battery; leave those systems to a shop.
• The same code returns after a repair.

The check question

Ask: Where is the diagnostic port on most cars? Answer: Under the dashboard on the driver's side

From EveryManKnows. General information, not professional advice.