1999 Toyota Camry P0171 and P1133 Diagnosis: Fuel Lean and O2 Sensor Circuit Issues

Start by testing the oxygen sensor's ability to switch between lean and rich conditions — if it fails to cycle properly, that could indicate a faulty sensor or underlying issues like vacuum leaks. If the sensor doesn

I recently fixed my 1998 Toyota Camry four-cylinder with similar codes: P0171, P1130, and P1133. I replaced the O2 sensor (located near the radiator in the exhaust system) with a $103 Bosch unit — but the problem persisted. A mechanic friend advised me to clean the old O2 sensor using carburetor cleaner and an old toothbrush instead of replacing it. He noted that Toyota oxygen sensors are high-quality and typically don't fail outright; they often just become clogged or dirty over time. After cleaning and reinstalling, my car stopped exhibiting rough idling, and the check engine light turned off on its own. I'm not a professional mechanic, but this simple fix worked for me. Try it — it might solve your issue. Another tip: Check Craigslist or local auto parts groups for a similar-year, same-model vehicle being sold at low price. Often, these cars are just being scrapped and have spare sensors, vacuum switches, and other components available for under $100. If you can acquire key parts like O2 sensors and vacuum lines for around $50–$100, you could swap them in to isolate the root cause of the problem. This approach helps identify faulty components without spending heavily on new parts. Hope this helps!