Check engine light codes

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01-14-18 | 11:46 AM

babymandm

Thread Starter

Driver School Candidate

Joined: Jan 2018

Posts: 18

Likes: 0

From: PA

Check engine light codes

Just got my 99 RX300 and it was fine when I left the used car lot, but of course now that I’ve had it a few days the engine light came on. I took it to my local auto parts store to get the codes and they are as follows:

P0171 - System Too Lean (Bank 1)

P0125 - Insufficient Coolant Temp For Closed Loop Fuel Control

P1135 - A/F Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)

P1155 - A/F Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)
Can someone explain what these mean and if it’s bad to run it with these codes? The auto store guy just said it’s an 02 Sensor but ge didn’t know If the car had 2 or 3 sensors in them and the P0125 he really didn’t explain. But he said he don’t think the other have anything to do with that one. It never fails!

Any help would be greatly appreciated! Also includes some pics of her! I’m very Happy other than the engine light. ☹️

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01-14-18 | 04:59 PM

carguy07

Lexus Champion

Joined: Nov 2005

Posts: 2,110

Likes: 74

From: OH

Ignore the P0125 code. There are 2 air fuel sensors and 1 oxygen sensor. Your issue is with one or both of the air fuel sensors. They are in the exhaust manifolds. Replace with OE or Denso 234-9009. You could clear the codes and see which one comes up first and replace that one and see what happens... or just replace both and you will probably be good to go. You don't want to drive around much in limp mode as you will be puking gas out the exhaust and heating up the converters.

All you need is here: https://www.clublexus.com/forums/rx-...el-sensor.html

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