Failing O2 Sensor Triggers Rich Fuel Mix in Enclave

Let me share my experience with a similar issue on my 2015 Buick LaCrosse. I have some experience working on cars, mainly basic maintenance and diagnostics. The symptoms you describe match what I encountered, poor fuel economy and check engine light due to a faulty oxygen sensor heater element. Initially thought it was just a loose connection, but diagnostic testing confirmed the sensor itself was failing. My repair involved: Complete sensor testing and voltage checks, Discovering a damaged wire harness connector at the oxygen sensor, Replacing the connector and cleaning all contact points, Final testing to ensure proper air-fuel ratio readings Total repair cost was 95 Euro, mainly labor since only the connector needed replacement. The job took about an hour at the shop. The vehicle emissions returned to normal after the repair. To help diagnose your situation better, could you share: Current mileage on your Enclave, Whether the check engine light is steady or flashing, Which oxygen sensor is showing the fault (Bank 1 or Bank 2), Any other symptoms like rough idling or hesitation These details would help determine if your issue is similar to what I experienced or if additional components need inspection.

I checked my records and my current mileage is 107068 KM. The repair cost estimate sounds about right based on part prices. The malfunction indicator has been steady, not flashing, and preliminary testing shows Bank 1 sensor failing. No rough idling, just the increased fuel usage. The exhaust system looks clean otherwise, so hoping its isolated to just the sensor replacement. Will get it scheduled for repair next week.

Thanks for those details. Sounds nearly identical to what I experienced with my LaCrosse. Since you mentioned the steady check engine light and Bank 1 sensor, this really confirms my initial thoughts about the heater element failure being the culprit. The clean exhaust system is a good sign. When I had my repair done, the technician mentioned that oxygen sensor issues caught early typically dont cause additional exhaust system damage. My vehicle emissions returned to normal almost immediately after the repair. The fuel consumption should improve significantly once fixed. After my sensor replacement, I noticed better fuel economy within the first tank of gas. The heater element failure was causing my engine to run rich just like yours. Given the similar mileage and symptoms, this should be a straightforward fix. The oxygen sensor testing results and lack of rough idle suggest there arent any underlying issues to worry about. My repair has held up well for over 40,000 km now with no recurring problems. Keep us posted on how the repair goes. Based on my experience, you should see quick improvements in fuel economy once the new sensor is installed.

Thanks everyone for the helpful feedback. Going to move forward with the repair since all signs point to just the oxygen sensor heater element being the issue. Good to hear these repairs typically hold up well and that vehicle emissions should return to normal quickly. The steady malfunction indicator light and testing results make me confident its not a bigger problem. Will schedule the sensor replacement next week and update once its fixed. Really appreciate the insights on repair costs and confirmation that the clean exhaust system likely means no additional issues to worry about.