1999 Acura RL P0151, P0150, P0173, P0174 OBD2 Codes - Diagnosis and Fixes
Hi, I own a 1999 Acura RL 3.5L with recent OBD2 trouble codes: P0151, P0150, P0173, and P017-than. Despite these codes, the car runs smoothly and performs well under normal conditions. The issue is intermittent — one day I get P0151, clear it, and the next day P0173 or P0174 appears. What could be causing this? I've ordered a new O2 sensor and plan to install it next week to see if that resolves the problem. Any insights or recommendations would be greatly appreciated.
The P0150 and P0151 codes refer to Bank 2 Sensor 1 O2 sensor (pre-cat) — this is the upstream oxygen sensor located before the catalytic converter. If your vehicle has high mileage or original equipment, replacing both Bank 2 pre-cat O2 sensors is recommended. These sensors are critical for fuel trim calculations and engine performance. Before addressing P0173 and P0174 (which relate to fuel trim issues on Bank 2), ensure the upstream O2 sensor signals are functioning properly. Possible causes include damaged or corroded O2 sensor signal wires between the sensor and PCM, or loose connectors. If you have access to a scan tool with live data streaming capabilities, perform an integrity test on the O2 sensor signal wiring. For high-mileage vehicles, replacing both pre-cat O2 sensors is often the most effective solution.