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Our 2000 Toyota Tacoma just failed a smog check with the code PO171.

Our 2000 Toyota Tacoma just failed a smog check with the code PO171 and I was wondering what the problem could be. The code says the system is to lean. We are changing the filter, oil, and spark plugs. Will this get us to pass? Thank you very much for the help.
Answer:

Changing the oil filter and spark plugs on your Toyota Tacoma is great maintenance but I'm afraid it will not fix a lean fuel condition. Changing the fuel filter on the other hand (only if the current one is plugged and restricting fuel flow) will help fix a lean fuel mixture. The most important thing here is to find out why your vehicle is running lean. The problem can either be mechanical or electronic. If mechanical we recommend inspecting anything that might cause the fuel system to run lean, i.e.. vacuum leaks, disconnected hoses, restricted fuel filter. If the problem is determined to be electrical, the first component we'd suspect is the oxygen sensor. If this doesn't work, the next component which could be the culprit would be the mass air flow sensor. Keep in mind with a computer controlled engine such as this, there are several components which play a role in determining fuel ratio. Along with the O2 (Oxygen Sensor), components such as the TPS (Throttle Position Sensor), ECT (Engine Coolant Temperature Sensor) and MAF (Mass Air Flow Sensor) sensors send vital engine information to the computer which is used to determine proper air to fuel ratio. If any one of these components are defective they can alter the fuel delivery program. A smog service station would be able to diagnose each component and report it's condition. posted by SmogTips Support

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