P0137 on a Hyundai: Causes, Fixes & Repair Cost

🟢 Low severity · drivable

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

What P0137 means on a Hyundai

On a Hyundai, P0137 means the engine computer sees low voltage from the bank 1 downstream oxygen sensor, the one behind the catalytic converter. This sensor only checks converter efficiency, so low voltage is usually a faulty sensor, damaged wiring, or an exhaust leak rather than a fuel problem. Hyundai four-cylinder models have a single bank, so bank 1 covers all cylinders.

Is P0137 common on Hyundais?

P0137 shows up on higher-mileage Hyundais as the downstream sensor wears out or its wiring is damaged by exhaust heat. It is often seen on older Elantra and Sonata models, and a small exhaust leak before the sensor can produce the same low-voltage reading.

Commonly reported on: Elantra, Sonata, Tucson, Santa Fe.

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: Sensor wiring damaged by exhaust heat
less common: Corroded sensor connector

How to fix it

Fix	DIY?	Typical cost
Replace the bank 1 downstream oxygen sensor	Yes	$60–220
Repair an exhaust leak near the sensor	Mechanic	$80–280
Repair damaged O2 sensor wiring	Mechanic	$60–200