I'm experiencing a recurring issue with my 2003 Chevrolet Tahoe (5.3L V8) where all four oxygen (O2) sensors are showing low circuit voltage, triggering diagnostic trouble codes P0131, P0137, P0151, and P015
Thanks for the reply. I recently replaced the fuel filter and noticed a significant improvement in starting performance. I also removed all O2 sensors to inspect them—no visible buildup or corrosion, so they appear clean. The check engine light turned off after this. I suspect the issue was caused by poor-quality fuel introduced during winter months in Montana. I've now added a fuel treatment product designed for water and sediment removal. No aftermarket parts, no vacuum leaks, not flex fuel—everything is stock. I'm still concerned about dirty injectors, especially since the old filter had been in use for years. Symptoms included severe power loss, sluggish starts, high RPM shifts, poor fuel economy, and overall frustration. It felt like a carbureted engine issue—but with modern electronic systems. I bought this vehicle 5 months ago and likely experienced bad fuel during winter. I'll update after running the treatment and monitoring performance over the next few weeks.
All these codes point to a lean exhaust condition—first check for vacuum leaks. Ensure there are no other related codes present. Is this vehicle running on regular gasoline? Has any flex fuel been introduced? The engine is stock with no aftermarket modifications (no performance parts, filters, spark plugs, or thermostats). Verify that the underhood fuse box fuses for O2A and O2B are intact and not blown. Use an OBD2 scanner to check sensor return voltage—does it consistently read low? Try spraying carburetor cleaner into the throttle body; does this cause a temporary change in readings? Monitor fuel trims: are they showing +10 or more? If so, that indicates a lean condition. Consider checking fuel pressure with a gauge to rule out fuel delivery issues.