'00 Es300 P0171 Code

[eugenez]

Hi guys,

I have a little dilema. My check Engine light came on and it showed P0171 Code. System to Lean Bank 1. I cleaned the MAF sensor and changed the air filter and fuel filter. Checked all of my vacuum lines and fuel lines. Can some one help me figure out the problem without changing the sensor. If needed to change the sensor, do I need to change the MAF sensor or the Bank 1 Sensor 1. I have cleared the code a few times but after like 2-5 miles it comes back on. Please help.

[George_Jetson]

Has any work been done recently, such as changing valve cover gaskets? If you have access to a scanner, you could check the fuel air sensor response by monitoring the output while adding extra fuel (ie such as propane from a un-lite propane torch). Otherwise you could swap sensors with bank 2 (make sure the connector is the same first). You did not mention what the mileage is.

[eugenez]

Has any work been done recently, such as changing valve cover gaskets? If you have access to a scanner, you could check the fuel air sensor response by monitoring the output while adding extra fuel (ie such as propane from a un-lite propane torch). Otherwise you could swap sensors with bank 2 (make sure the connector is the same first). You did not mention what the mileage is.

No work has been done ever since I bought it in 2006. I did have an oxygen sensor go out on me like 2 years ago but I have replaced that and it was working fine ever since. I have 90000 miles on it.

[Vinodh]

Hi guys,

I have a little dilema. My check Engine light came on and it showed P0171 Code. System to Lean Bank 1. I cleaned the MAF sensor and changed the air filter and fuel filter. Checked all of my vacuum lines and fuel lines. Can some one help me figure out the problem without changing the sensor. If needed to change the sensor, do I need to change the MAF sensor or the Bank 1 Sensor 1. Please help.

Did you clear up the code after changing the air filter and fuel filter? I had this code couple of weeks back read out at Autozone. I just did the oil change with air filter changed. I did not feel anything different when i drive, so we just reset code and it did not come again after that.

[George_Jetson]

Do you remember which O2 sensor you replaced? Ideally, if you have a scanner that allows you to monitor the sensor voltage, I would recommend adding propane to force a rich condition while monitoring the sensor output. This will tell you if the sensor is working. Otherwise you could look into swapping Bank 1 sensor 1 and bank 2 sensor 1

[eugenez]

Do you remember which O2 sensor you replaced? Ideally, if you have a scanner that allows you to monitor the sensor voltage, I would recommend adding propane to force a rich condition while monitoring the sensor output. This will tell you if the sensor is working. Otherwise you could look into swapping Bank 1 sensor 1 and bank 2 sensor 1

I have a scanner that just reads codes. How do you add the propane and where do you add it to?

[George_Jetson]

Without being able to monitor the output, adding propane would not tell you anything. The idea is that higher end scanners will show you the actual voltage in real time. If you spray propane into the airflow meter you will see the O2 sensors putting out a high voltage.

[eugenez]

Problem Solved. I changed out my MAF Sensor and Check Engine light Never came back on. Maybe some one needs this information. Good Luck!!!!!

[PETER PAN]

GS300 with 85K miles had code P0171 and P0174.

MAF resistance measured OK. Clean it with carburator cleaner, did not help.

Swapped in a MAF sensor form another car. Cleared all codes. Pass smog test. Car runs smooth and powerful again.