2006 high ling term fuel trim P0171
Super Moderator
Joined: Jan 2008
Posts: 15,179
From: PTW
Downstream O2 sensor is supposed to monitor the CAT's performance. The upstream A/F sensor generates the signal for air/fuel mixture.
How is the trim with engine cold. The A/F system supposed to be off when engine first starts up.
Some auto parts stores will read codes.
Is the check engine light on?
How is the trim with engine cold. The A/F system supposed to be off when engine first starts up.
Some auto parts stores will read codes.
Is the check engine light on?
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Junior Member
Joined: Mar 2019
Posts: 16
Downstream O2 sensor is supposed to monitor the CAT's performance. The upstream A/F sensor generates the signal for air/fuel mixture.
How is the trim with engine cold. The A/F system supposed to be off when engine first starts up.
Some auto parts stores will read codes.
Is the check engine light on?
How is the trim with engine cold. The A/F system supposed to be off when engine first starts up.
Some auto parts stores will read codes.
Is the check engine light on?
I forgot to mention that it is throwing a P0171 code.
the trim is about 10% when first started up, but increases fast with any kind of rpm.
Super Moderator
Joined: Jan 2008
Posts: 15,179
From: PTW
Search the internet for "P0171 pdf". As in pdf files. You may find pdf files and YouTube videos.
Toyota has a list of issues that can cause this code which is System Too Lean. The code is generic car among car manufacturers.
Below are the list of potential causes and my opinion.
Air induction system. Look for air intake leaks - Does happen. View YouTube videos on how to check for leaks.
Injector blockage. Seldom an issue. Engine would run rough.
Mass air flow meter. Happens. Can use OBDII reader to check voltage output from MAF. Try cleaning MAF. Watch a few YouTube videos on this.
Engine coolant temperature sensor. This is the coolant temp sensor for computer. You can read the sensor temp using an OBDII code reader and determine if it is inaccurate.
Fuel pressure. Seldom an issue. To check this requires installing a pressure gauge.
Gas leakage in exhaust system. Check the flex exhaust pipe between engine exhaust pipe and under chassis pipe. Happens. You should be able hear of feel the exhaust leak.
Open or short in A/F sensor (bank 1, sensor 1),
Circuit A/F sensor (bank 1, sensor 1).
A/F sensor heater (bank 1, sensor 1).
All 3 above refer to the A/F sensor before the emissions converter. This sensor is a No 1 cause. A code reader can check sensor voltage.
EFI M relay. Uncommon.
PCV valve and hose
PCV hose connection
The above 2 refer to air leaks in the PCV system. Happens and easy to check.
Toyota has a list of issues that can cause this code which is System Too Lean. The code is generic car among car manufacturers.
Below are the list of potential causes and my opinion.
Air induction system. Look for air intake leaks - Does happen. View YouTube videos on how to check for leaks.
Injector blockage. Seldom an issue. Engine would run rough.
Mass air flow meter. Happens. Can use OBDII reader to check voltage output from MAF. Try cleaning MAF. Watch a few YouTube videos on this.
Engine coolant temperature sensor. This is the coolant temp sensor for computer. You can read the sensor temp using an OBDII code reader and determine if it is inaccurate.
Fuel pressure. Seldom an issue. To check this requires installing a pressure gauge.
Gas leakage in exhaust system. Check the flex exhaust pipe between engine exhaust pipe and under chassis pipe. Happens. You should be able hear of feel the exhaust leak.
Open or short in A/F sensor (bank 1, sensor 1),
Circuit A/F sensor (bank 1, sensor 1).
A/F sensor heater (bank 1, sensor 1).
All 3 above refer to the A/F sensor before the emissions converter. This sensor is a No 1 cause. A code reader can check sensor voltage.
EFI M relay. Uncommon.
PCV valve and hose
PCV hose connection
The above 2 refer to air leaks in the PCV system. Happens and easy to check.
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