Two free tools for everyday car owners. The maintenance interval planner takes your current mileage and the mileage of your last services and shows what is overdue, due soon or coming up. The OBD-II code lookup explains about 50 of the most common generic P0 trouble codes in plain English, with typical causes and how urgent each one usually is. Both run in your browser and use only what you type.

Maintenance interval planner

OBD-II code lookup

How to use these numbers

Maintenance planner

• Start with your manual. Replace the default intervals with your vehicle's numbers, choosing the severe-service schedule if it applies. Our normal vs. severe schedule guide explains how to decide.
• No records? If you bought the car used without receipts, enter 0 as the last service for any item you cannot verify. It will show as overdue, so you can service it and start a fresh record from that mileage.
• Remember time limits. A low-mileage car still needs oil, brake fluid and coolant changes on a calendar schedule.
• Bundle jobs. If several items fall due within a few hundred miles of each other, doing them together saves time and shop visits.

Code lookup

• Record before clearing. Save all codes and freeze frame data before clearing anything.
• Fix the cause, not the code. A code tells you which test failed. Use the causes as a checklist to test, and read our check engine light and OBD-II guide for a step-by-step workflow.
• Multiple codes matter together. P0171 with P0174 points to a cause affecting both banks, such as a vacuum leak or MAF sensor, while a single-cylinder misfire points to that cylinder's plug, coil or injector.
• Low-voltage codes can mislead. A weak battery can set odd codes; test it with our battery testing guide.