OBD2 Error Code Reference
Look up any OBD2/OBDII diagnostic trouble code — plain-English description, common causes, severity, and repair cost estimate.
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Common codes:
OBD2 Code Structure Guide
| First Letter | System | 2nd Digit | Example Codes |
|---|---|---|---|
| P — Powertrain | Engine, fuel, ignition, transmission, emissions | 0 = generic, 1 = OEM-specific | P0420, P0300, P0171 |
| B — Body | Airbags, climate control, lights, windows, seats | 0 = generic, 1 = OEM-specific | B0001, B1001 |
| C — Chassis | ABS, traction control, steering, suspension | 0 = generic, 1 = OEM-specific | C0035, C1201 |
| U — Network | Module communication, CAN bus, wiring network | 0 = generic, 1 = OEM-specific | U0100, U0121 |
P0xxx = SAE generic codes (all makes). P1xxx = Manufacturer-specific (varies by brand). Always clear codes after repair and complete a full drive cycle to confirm the fix.
How to Use an OBD2 Scanner
Plug the scanner into the OBD2 port (under the dashboard, driver's side, usually near the steering column). Turn the ignition to the "on" position without starting the engine. The scanner will read all stored DTCs (Diagnostic Trouble Codes). After repairing, clear the codes and drive a full cycle (typically highway + city driving) to let the monitors reset and confirm the repair.
Pending vs. Confirmed vs. Permanent Codes
A "pending" code means the fault occurred once but hasn't triggered the MIL (Check Engine Light) yet. A "confirmed" code has triggered the light. A "permanent" code cannot be cleared by a scanner — it requires a completed drive cycle after the underlying fault is fixed. Never clear codes before an emissions test unless you've already fixed the underlying issue and completed drive cycle monitoring.
When to Drive vs. Stop Immediately
Flashing Check Engine Light = misfire damaging your catalytic converter. Stop soon and get it checked. Steady Check Engine Light with no other symptoms = usually driveable for days to weeks, but get it diagnosed. Check Engine Light + overheating + unusual noise = stop immediately. The code is a starting point for diagnosis, not a guaranteed repair prescription.