P0137 on a GMC: Causes, Fixes & Repair Cost

🟢 Low severity · drivable

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

What P0137 means on a GMC

On a GMC, P0137 means the engine computer sees low voltage from the bank 1 downstream oxygen sensor, located after the catalytic converter. This sensor only checks converter efficiency, so low voltage usually means a faulty sensor, damaged wiring, or an exhaust leak rather than a fuel problem. On V8 trucks and SUVs, bank 1 is the right-hand bank.

Is P0137 common on GMCs?

P0137 shows up on higher-mileage GMC trucks and SUVs as the downstream sensor ages. Exhaust leaks at the manifold or pipe joints are a common trigger on V8 models, and wiring in the exhaust area can become brittle from heat.

Commonly reported on: Sierra, Yukon, Terrain, Acadia.

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: 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	$60–240
Repair an exhaust leak near the sensor	Mechanic	$80–300
Repair damaged O2 sensor wiring	Mechanic	$60–200