Lexus 2000 Rx300 P0171 System Too Lean Bank 1

Sami · August 17, 2006

Hello Group,

It's been a month but I and my mechanic couldn't find out what sensor to change for error code P0171 System Too Lean Bank 1. Here what have been done?

* Detailed Tue-up

* Clean Manifold System by flushing (he used some engine clean chemicals)

* Clean MAF Sensor through 91% Alcohol

* Swap O2 sensors the one close to engine (left) with the one before catalytic converter

Since day 1 we are getting same error after reset and work done on the car. I know this mechanic that he is working with cars for at least last 15 years. This is his professional, but could figure out what cause the engine light. Any advice will be appreciated. I am trying to avoid dealer just to save few $$$. I am located Dallas area, if anyone advises a cheap mechanic i would appreciate too.

Also - how to get a map to find the location of all sensors on Lexus. I might try myself to swap/clean. Just like i cleaned MAF sensors. Thanks Again Sam

Benjamin Tang · August 17, 2006

just a shot in the dark.... has anyone pulled the spark plugs (both the lean plug and at least one of the other ones to compare) to see what condition it's in?

this is all i could find on the other board:

http://www.clublexus.com/forums/showthread...;highlight=lean

edit: coil pack has nothing to do with this problem...

Sami · August 17, 2006

just a shot in the dark.... has anyone pulled the spark plugs (both the lean plug and at least one of the other ones to compare) to see what condition it's in?

this is all i could find on the other board:

http://www.clublexus.com/forums/showthread...;highlight=lean

edit: coil pack has nothing to do with this problem...

Thanks for the reply. The check engine light were on before tune-up. He replaced spark plugs after tune-up (I belive he used regular plugs not the expansive one -- radian etc)

sam

SKperformance · August 17, 2006

Do a search on your engine code which is a common one and see what you find.

Ericok · August 18, 2006

Do a search on your engine code which is a common one and see what you find.

For code P0171: 9 out of 10 times, if you can't get the MAF sensor clean, you need a new one. There are literally hundreds of posts on the internet about this problem (not just involving Lexus/Toyota). Almost all end up with a new MAF. Rockauto (www.rockauto.com) will sell you a rebuilt MAF for less than $80. A new MAF is $140-$300 depending on who makes it and who sells it.

Having said that, the other items worth looking at are: air leak, fuel pressure, clogged injector, coolant temp sensor, or 02 sensor.

Sami · August 18, 2006

Do a search on your engine code which is a common one and see what you find.

For code P0171: 9 out of 10 times, if you can't get the MAF sensor clean, you need a new one. There are literally hundreds of posts on the internet about this problem (not just involving Lexus/Toyota). Almost all end up with a new MAF. Rockauto (www.rockauto.com) will sell you a rebuilt MAF for less than $80. A new MAF is $140-$300 depending on who makes it and who sells it.

Having said that, the other items worth looking at are: air leak, fuel pressure, clogged injector, coolant temp sensor, or 02 sensor.

Ericok, Thanks for the reply. I did clean MAF sensor before with alcohol. I wasn't comfortable with the cleaning. Therefore yesturday I bought CRC MAF cleaner sprayer and clean the sensor. Also - this time instead the resetting the engine light error code, i did recycle the power by diconnecting battery. So far i haven't seen light come on since yesturday. I hope it keep that way.

The site (www.rockauto.com), i check the price for MAF. I got confused with pricing. The first column says $71 than second column heading core said $49. what is this core price for?

sv650rx300 · August 20, 2006

Do a search on your engine code which is a common one and see what you find.

For code P0171: 9 out of 10 times, if you can't get the MAF sensor clean, you need a new one. There are literally hundreds of posts on the internet about this problem (not just involving Lexus/Toyota). Almost all end up with a new MAF. Rockauto (www.rockauto.com) will sell you a rebuilt MAF for less than $80. A new MAF is $140-$300 depending on who makes it and who sells it.

Having said that, the other items worth looking at are: air leak, fuel pressure, clogged injector, coolant temp sensor, or 02 sensor.

Ericok, Thanks for the reply. I did clean MAF sensor before with alcohol. I wasn't comfortable with the cleaning. Therefore yesturday I bought CRC MAF cleaner sprayer and clean the sensor. Also - this time instead the resetting the engine light error code, i did recycle the power by diconnecting battery. So far i haven't seen light come on since yesturday. I hope it keep that way.

The site (www.rockauto.com), i check the price for MAF. I got confused with pricing. The first column says $71 than second column heading core said $49. what is this core price for?

I also had P0171 on my 2000 RX300 AWD, about 70,000 miles

I think it is fixed now, because light has not come on and it has about 70 miles and probably 10 times engine on/off since the last code reset (disconnected battery).

I saw two problems when fixing the car:

1. Bad air/feul ratio sensor bank 1 sensor 1 (resistance was virtually zero, meaning heater circuit is short)

2. Damaged O-ring on MAF sensor. I carefully cleaned the sensor using a small paint brush and electrical contact cleaner. Then I put a new O-ring, coated with light engine oil on the sensor.

If the CEL comes on again on mine, I think I'll check fuel pressure. But as I mentioned, it is probably fixed.

Sometimes O-ring was overlooked, leakage might be enough to cause CEL.

Good Luck.

Ericok · August 20, 2006

Do a search on your engine code which is a common one and see what you find.

For code P0171: 9 out of 10 times, if you can't get the MAF sensor clean, you need a new one. There are literally hundreds of posts on the internet about this problem (not just involving Lexus/Toyota). Almost all end up with a new MAF. Rockauto (www.rockauto.com) will sell you a rebuilt MAF for less than $80. A new MAF is $140-$300 depending on who makes it and who sells it.

Having said that, the other items worth looking at are: air leak, fuel pressure, clogged injector, coolant temp sensor, or 02 sensor.

Ericok, Thanks for the reply. I did clean MAF sensor before with alcohol. I wasn't comfortable with the cleaning. Therefore yesturday I bought CRC MAF cleaner sprayer and clean the sensor. Also - this time instead the resetting the engine light error code, i did recycle the power by diconnecting battery. So far i haven't seen light come on since yesturday. I hope it keep that way.

The site (www.rockauto.com), i check the price for MAF. I got confused with pricing. The first column says $71 than second column heading core said $49. what is this core price for?

Alcohol isn"t strong enough to clean the MAF sensor. Using CRC was the right choice. Rockauto wants your old senor back in order to send to the rebuild shop (for the next customer). You pay the MAF cost PLUS the core charge when you buy your sensor. When you send in the sensor you've removed from your the car, they refund the core charge. It's a common practice in the auto parts business. That's how rebuilders get stuff to rebuild. It's going to take a few drive cycles to be sure you've fixed the problem. If it hasn't come back on after about a week, you should be OK.