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CEL P0171 - System Too Lean (Bank 1)


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#1 Haulin

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Posted 15 May 2012 - 07:00 AM

My 1ZZ ā€“ 5spd has about 287,000KM on it & I have been noticing the smell of raw fuel when I start it (warm & cold). On the way to work yesterday the check engine light came on. When I got home, I read & reset the code.

A single CEL code: P0171

Car still runs fine & has lots of power.

So here is my plan of action:
- change the air filter (way overdue)
- clean the MAF (using non-chlorinated electronics cleaner)
- likely be no change ā€“ so next replace the leaking exhaust donut.
- if still no change - replace the O2 sensor?
- any other ideas?

Iā€™m taking the car to the west coast again in a month or two & I want to be sure I makes it back. lol

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#2 DaOne

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Posted 15 May 2012 - 01:38 PM

when was the last time you changed your air filter

#3 Duke91

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Posted 15 May 2012 - 01:40 PM

Manifold gasket. Or vaccum lines could be dissconnected or punctured..
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#4 hughesjasonk

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Posted 15 May 2012 - 02:50 PM

it could be an exhaust leak..... with that many miles chances are it's time to change the o2 sensor.
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#5 Haulin

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Posted 16 May 2012 - 10:32 AM

View PostDaOne, on 15 May 2012 - 01:38 PM, said:

when was the last time you changed your air filter

I changed it yesterday, but yah it had been nearly 90, 000KM. lol
I have put about 140KM on it since reset & the CEL has not returned.

View Posthughesjasonk, on 15 May 2012 - 02:50 PM, said:

it could be an exhaust leak..... with that many miles chances are it's time to change the o2 sensor.

I replaced the exhaust donut on borth of the 1ZZ's I owned previously. Hard shifts, clutch drops & engine braking causes the engine to move quite a bit; this flattens out the donut between the exhaust manifold and the exhaust pipe. Then they leak. After I clean the MAF, it will be the next thing I do.

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#6 Salsa Guy

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Posted 18 May 2012 - 12:57 AM

View PostDuke91, on 15 May 2012 - 01:40 PM, said:

Manifold gasket. Or vaccum lines could be dissconnected or punctured..
X2 This! Don't waste money or time on the MAF or O2.
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#7 delvallexrs

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Posted 18 May 2012 - 01:18 AM

do a fuel injector cleaning service and clean the injectors, have u check in to the fuel filter make sure is not getting clogged and if u getting a bank 1 lean code the it should be ur O2 sensor the one before the cat

#8 Haulin

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Posted 30 May 2012 - 06:35 AM

The CEL never did return - just needed an air filter. LMAO

#9 Elmacanite

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Posted 14 June 2012 - 03:00 PM

Good to hear but if you haven't replaced your intake manifold gasket I'd go get the updated part from whatever Toyota dealership you're closest to...it's like $5 and replaces the factory one that degrades and can cause that same CEL

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