P2A00 on Toyota: Causes, Symptoms and Fix Cost

The Quick Answer above is the generic definition. What follows is the model-specific detail for the Toyota models that log P2A00.

Beyond the generic causes listed on the main P2A00 page, these are the patterns noted for Toyota models:

Follow these steps to pinpoint the root cause of P2A00:

1. Read every stored code and the freeze frame. Deal with sensor heater codes, fuel trim codes, misfires and airflow sensor faults first, because each of them can make a healthy sensor fail this test
2. Watch the upstream sensor on a generic OBD2 reader with the engine fully warm. On a wideband sensor the reading should move promptly toward lean when you lift off the throttle (fuel cut) and toward rich on firm acceleration. On the second-generation Prius, for example, Toyota's manual notes that a generic OBD2 scan tool shows this sensor at about 0.66 V at the ideal mixture where Toyota's own tester shows about 3.3 V; check how your car reports it before judging the reading, and do not mistake it for a narrowband signal
3. Check the long-term fuel trims. Trims far from zero point to a real lean or rich mixture (air leak, exhaust leak, fuel pressure or injector fault) rather than a lazy sensor
4. Check for exhaust leaks ahead of the sensor and for intake leaks with a smoke test, including the PCV hose and its connections
5. Check the sensor heater supply: the fuse, the relay and the heater resistance across the heater pins with the sensor unplugged, against the manual's value
6. A generic reader cannot run the manufacturer's active test that forces the mixture rich and lean to time the sensor; a workshop with the maker's tester can. If everything else checks out, fit a sensor that matches the original part number, clear the code and drive a full warm-up cycle including steady cruising, then check the readiness status and, where the car reports it, the Mode 06 result

Estimated repair costs for P2A00 in EUR, compiled across makes. Toyota costs typically sit in the middle of each range.

These codes are often seen alongside P2A00 or point to related issues, on any make: