Lexus 300 P0171

[davidditt]

Hey guys. A lot of discussion on the P0171 error and the MAF sensor, but before I go out and buy one I wanted to make sure as much as possible that I wasn't chasing another problem. My 1999 Lexus RX300 is running rough and missing out some and I'm getting P0171 error first, then 1130,1135,1150,1155 and sometimes if I let it go long enough the coil codes start, 301,302 etc. I cleaned the MAF sensor and it ran pretty well with no error code for an hour or so then started with the error codes and running rough again. Sure seems like the MAF sensor, but didn't want to invest in an MAF, then an O2 etc. if I should be doing something else. Thanks in advance.

[code58]

David- The test for the sensor is: 68 degrees F, looking into the socket inlet to the meter (pins), use a DVM with + on the far left pin (E2) and the - on the next pin (THA) the reading should be 2.21-2.69 k ohms resistance. Inspecting the MAF Meter operation: with the MAF meter out of the intake tube but CONNECTED to the plug, turn the ignition ON and using a volt meter probe the + test probe into the center wire (past the insulator) and the - probe into the one next right (4th over from the left, this is all facing the same way you were when you identified the E2 &THA). Blow air into the MAF opening (where the intake air would pass through) and check to see that the voltage fluctuates. Turn the ign. switch off. If it fails either one of these tests, it's bad. That is straight from the Lexus shop manual. Hope that helps. Don't chase any of the other codes, when you have that many, clear them all and see what comes up 1st.

[davidditt]

David- The test for the sensor is: 68 degrees F, looking into the socket inlet to the meter (pins), use a DVM with + on the far left pin (E2) and the - on the next pin (THA) the reading should be 2.21-2.69 k ohms resistance. Inspecting the MAF Meter operation: with the MAF meter out of the intake tube but CONNECTED to the plug, turn the ignition ON and using a volt meter probe the + test probe into the center wire (past the insulator) and the - probe into the one next right (4th over from the left, this is all facing the same way you were when you identified the E2 &THA). Blow air into the MAF opening (where the intake air would pass through) and check to see that the voltage fluctuates. Turn the ign. switch off. If it fails either one of these tests, it's bad. That is straight from the Lexus shop manual. Hope that helps. Don't chase any of the other codes, when you have that many, clear them all and see what comes up 1st.

[davidditt]

thanks for the advice code 58. It seemed to check out okay but Autozone had the sensor for $69.00 so I thought I'd give it a try. Same code same running rough. PO171, sometimes 072, and still the 1130,1135,1150,1155. Any ideas?

Thanks

[davidditt]

Another piece of the puzzle. Seems like PO125 is now the first error code to come up. Don't think that one is supposed to make the engine run rough however. The coolant level was low but only by a quart or so. Anyhow, don't know if that helps.

[iolmaster]

I also had P0171 and no others. I had already replaced the two A/F and oxygen sensors. Car has 122,000 miles on it so these are going at about the right time. I had read that the MAF sensor was common with P0171 so I thought I would give it a try since I could get a remanufactured sensor from Advance auto for $80.00. I changed it about a week ago and cleared the codes and the light has not come back on in about 200 miles. The engine is idling a bit slower also. It went from about 900 RPM to about 600 RPM. Seems to have done the trick.

[cuda]

thanks for the advice code 58. It seemed to check out okay but Autozone had the sensor for $69.00 so I thought I'd give it a try. Same code same running rough. PO171, sometimes 072, and still the 1130,1135,1150,1155. Any ideas?

Thanks

my 99 rx300 has 160,000km,first P171,I changed new MAF sensor from ebay cost me $100, then P171 came again and P1130(it should show you bank one or tow failure, that means O2 sensor dead), I changed two O2 sensors from dealer cost near $700, now it's OK,my bank two O2 sensor also is dead which near exhaust pipe,but now it's ok no error code show, I will change late if it show error again.

[davidditt]

Well I guess it's time I actually fix this thing. Still getting the 0171, 1130,1150. I'm starting to think that it's the oxygen sensors. I hate to randomly replace them on a guess, or a least start with the ones most likly to fail. Also, by the way, I took off the hoses going to the Air intakes and the one closest to the front of the car has got a lot of black gunk in it. The side closest to the windshield wasn't nearly so bad. Don't know if that helps or offers any clues. I guess my question now is; should I start changing oxygen sensors and if so which one first? Also am I doing any damage by driving it running rough like this. Thanks again for any help.