Trouble Code P0171 - Please Help

[Sofie]

1999 Lexus RX300 - check engine light on, car performance terrible, mpg too low / local mechanic told me the troube code was P0171 - they replaced the Air Mass Sensor and changed the spark plugs. All was fine for 8 days or so and yesterday the check engine light came on again! I brought it back to the mechanic who once again told me the trouble code was the same!

What else could it be?

[edbro]

Stolen from here: http://www.automotiveforums.com/t405771-ch...code_p0171.html

Brian R.05-13-2005, 09:26 PM

For P0171 code (easiest and cheapest first)

1. Check your air induction system for leaks or broken hoses/connections.

2. Put some injector cleaner into a tank of gasoline and see if that helps after you've gone through a tank of treated gas.

3. Buy some no-residue sensor or electronic contact cleaner (NAPA or elsewhere). Remove the connector from the MAF meter spray both sides of the connector thoroughly. Spray the cleaner into every possible exposed portion of the MAF meter in the intake tube and let the cleaner evaporate. Reconnect the MAF meter.

4. Test the engine coolant temperature sensor - replace if out of spec.

5. Check the manifold absolute pressure sensor - replace if out of spec.

6. Check your fuel pressure (not too likely to be the problem).

7. Replace the HO2/A-F ratio sensor with the correct sensor (Bank 1 Sensor 1) - Get a part number from a Toyota parts department with your VIN.

8. Replace the MAF meter.

Somewhere along this process, the light should go out and stay out. Most commonly, it is cleaning the MAF meter and connector that solves the problem. Unfortunately, the light can go out for a short period and then reappear - making you think you solved the problem.