P0133 on a GMC: Causes, Fixes & Repair Cost
🟠 Moderate severity · drivable
A GMC with P0133 usually still runs well, but fuel economy drops a bit until the sensor is replaced.
What P0133 means on a GMC
On a GMC, P0133 means the bank 1 upstream oxygen sensor is responding too slowly to changes in the exhaust. The computer uses this sensor to adjust the fuel mixture in the engine.
Is P0133 common on GMCs?
P0133 is common on GMC trucks and SUVs like the Sierra, Yukon, Terrain, and Acadia at higher mileage. The upstream sensor ages over time, and an exhaust leak at the manifold or pipe is a frequent companion cause.
Commonly reported on: Sierra, Yukon, Terrain, Acadia.
Symptoms
- Check engine light on
- Lower fuel economy
- Rough idle or hesitation
- Failed emissions test
Common causes
- most common: Aging upstream oxygen sensor (bank 1, sensor 1)
- common: Exhaust leak before the sensor
- common: Intake or vacuum leak affecting the mixture
- less common: Sensor wiring or connector damage
How to fix it
| Fix | DIY? | Typical cost |
|---|---|---|
| Check the exhaust and intake for leaks first | Yes | $50–150 |
| Replace the upstream O2 sensor | Yes | $80–220 |
| Repair the sensor wiring harness | Mechanic | $100–250 |
Frequently asked questions
Other common GMC codes
P0133 on other brands
Looking for the full (non-brand-specific) guide? See the P0133 code page →
Browse all GMC codes: GMC hub →
Updated 2026-08. This page is informational and not a substitute for professional diagnosis.