P0133 on a Lexus: Causes, Fixes & Repair Cost

🟠 Moderate severity · drivable

A Lexus with P0133 usually still drives fine, but fuel economy drops slightly until the sensor is replaced.

What P0133 means on a Lexus

On a Lexus, P0133 means the bank 1 upstream sensor is responding too slowly. Like other Toyotas, Lexus uses a wide-range air-fuel ratio (A/F) sensor in this position rather than a plain oxygen sensor.

Is P0133 common on Lexuss?

P0133 is common on higher-mileage Lexus models like the ES, RX, and GS. The A/F sensor ages over time, and because it's a wide-range sensor, the replacement part costs more than a standard O2 sensor.

Commonly reported on: ES, RX, GS, NX.

Symptoms

Check engine light on
Slightly worse fuel economy
Rough idle or hesitation
Failed emissions test

Common causes

most common: Aging air-fuel ratio sensor (bank 1, sensor 1)
common: Exhaust leak before the sensor
common: Sensor contaminated by oil or coolant
less common: Wiring or connector damage

How to fix it

Fix	DIY?	Typical cost
Check for exhaust leaks before replacing the sensor	Yes	$50–200
Replace the upstream A/F sensor	Yes	$120–300
Repair the sensor wiring or connector	Mechanic	$100–250