Q: P0171 System Too Lean (Bank 1) on 1999 Toyota Camry

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I have a 1999 Camry LE 5S-FE and it threw a P0171 code. I tested for vacuum leaks (visually and using a can of carb cleaner), did not find anything. What can I do next? I am trying to get a hold of a scan tool so I can gather freeze frame data and will report back. Which components can I test in the mean time? Thanks in advance for your help.

I did have a P0446 code 2-3 weeks ago, replaced the charcoal canister with one from the dealer and reset the code. The code was gone after that. Now, I have this P0171 code - can they be related? The P0171 code is the only one that exists right now.

(1) Answer
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Possible fuel filter, intake air tube leak from air cleaner to engine, low fuel pressure, 02 sensor, vacuum leak, maf sensor etc.....
Thanks. Fuel filter was replaced a couple years ago with one from the dealer. I've checked for air leaks and the intake tube was also replaced (from dealer) and has no cracks. The car drives normally without any hesitation in pickup or at a red light. The temp gauge is about a half cm below the half mark at normal operating temperature. It never reaches the half mark no matter how long the engine is on. It doesnt fluctuate either. Could this have anything to do with a faulty ECT sensor and thus the code for system too lean? What data should I look for when I have the scan tool?

Also, the car has a map sensor not maf.

Thanks for your help.