P0137 on a Lexus: Causes, Fixes & Repair Cost

🟢 Low severity · drivable

Safe to drive — this downstream sensor only monitors the catalytic converter, so a Lexus with P0137 can be driven while you arrange the repair.

What P0137 means on a Lexus

On a Lexus, P0137 means the engine computer sees low voltage from the bank 1 downstream oxygen sensor behind the catalytic converter. This sensor only monitors converter efficiency, so low voltage is almost always a faulty sensor, damaged wiring, or an exhaust leak rather than a fuel problem.

Is P0137 common on Lexuss?

P0137 is most common on higher-mileage Lexus models, where Denso downstream sensors age and start reading low. It is frequently seen on RX and ES models, and the usual fix is replacing the sensor with an OE-quality Denso unit.

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

Symptoms

Check engine light on
Usually no change in how it drives
Possible exhaust tick from a small leak
Slightly worse fuel economy if a leak is present

Common causes

most common: Faulty bank 1 downstream oxygen sensor
common: Exhaust leak before the downstream sensor
common: Damaged sensor wiring, sometimes from rodents
less common: Corroded sensor connector

How to fix it

Fix	DIY?	Typical cost
Replace the bank 1 downstream oxygen sensor with an OE-quality Denso unit	Yes	$80–280
Repair an exhaust leak near the sensor	Mechanic	$80–300
Repair rodent-damaged O2 sensor wiring	Mechanic	$100–350