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P0171 P0330 P1150 - 2000 RX300 2WD - Suggestions Please

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My RX300 has around 125k miles.
Timing belt was replaced at around 83k miles.
For last few years, it has check engine light.
Well before that, CEL was off and on for a year or so but since 2 years it's on constantly.
Here are the error codes from autozone:
P0171 System Too Lean (Bank 1)
P0330 Knock Sensor 2 Circuit (Bank 2)
P1150 A/F Sensor Circuit Range/Performance Malfunction (Bank 2 Sensor 1)
P0171 System Too Lean (Bank 1)

Not sure why P0171 is repeated twice.

I cleaned the MAF. It was all gray with dust build up. Now the resistors are clean.
That didn't change it.
It was running fine but since last few weeks, it struggles to get power, specially when stopped at traffic light.
Pushing pedal takes a bit before it moves forward.
So have to fix it.
Does Bank 1 mean upstream or downstream O2 sensor?
Can I get by replacing one at this time?
This is not my main vehicle. 
This is for groceries and short trips around town so don't want to spend dealer price for repairs.
Are eBay parts good? I see downstream ones as little as $20 and upstream are around $30.
For Denso, downstream is around $60 and upstream is around $140.

What about knock sensor? Does that one also need replacement?
That thing is even pricier at autozone. It was showing $250 while eBay has Denso ones for $25.

Finally, how much labor cost are we talking if I buy these and have it installed by local mechanic?

Lexus RX300 MAF Before After Cleaning-s.jpg

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  • 2 weeks later...

Thanks for reply.

I got a OBD2 Scanner and cleared codes.

I used app (OBD Car Doctor) and it showed few more codes but no p0125.
It has P0330 Knock Sensor 2 Circuit, P1150 as trouble codes and P1155 as pending codes. What's pending???
I've yet to see P0171 in any app after clearing it.
Attached is short/long term fuel trim with other sensor data.
Does it point to bad Bank2 A/F sensor1?
I can replace the front one behind the radiator myself I think, if that's the one I need to replace.


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When ever there is a knock sensor code, the ecu changes running parameters and the engine goes into a sort of limp mode to prevent damage. The knock sensors are down in the valley between the two cylinder heads where mice often will go. You most likely have either chewed up knock sensor harnesses or a bad knock sensor. I would probably get that fixed first and then go from there to see if it clears your other codes...

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