P0137 on a Toyota: Causes, Fixes & Repair Cost
🟠 Moderate severity · drivable
Safe to drive, but the check engine light stays on and the car may fail an emissions test until the sensor issue is fixed.
What P0137 means on a Toyota
On a Toyota, P0137 means the bank 1 downstream oxygen sensor is reporting low voltage. This sensor sits after the catalytic converter and mainly checks converter efficiency, so a low reading points to the sensor itself, its wiring, or an exhaust leak letting extra air in — not a fuel problem.
Is P0137 common on Toyotas?
P0137 shows up on higher-mileage Toyotas like the Camry, Corolla, and RAV4, where downstream sensors age and exhaust joints can leak. On Toyotas the most common cause is simply a worn sensor. It is a routine fix, and many owners replace the downstream sensor themselves.
Commonly reported on: Camry, Corolla, RAV4, Highlander.
Symptoms
- Check engine light is on
- No obvious driveability change in most cases
- Possible failed emissions test
- Occasional slight drop in fuel economy
Common causes
- most common: Worn or failing downstream oxygen sensor
- common: Exhaust leak ahead of the sensor
- common: Damaged or corroded wiring or connector
- less common: Defective aftermarket sensor
How to fix it
| Fix | DIY? | Typical cost |
|---|---|---|
| Replace the downstream oxygen sensor | Yes | $70–190 |
| Repair the exhaust leak | Mechanic | $100–300 |
| Repair the wiring or connector | Mechanic | $80–200 |
Frequently asked questions
Other common Toyota codes
P0137 on other brands
Looking for the full (non-brand-specific) guide? See the P0137 code page →
Browse all Toyota codes: Toyota hub →
Updated 2026-08. This page is informational and not a substitute for professional diagnosis.