12-31-2021, 10:14 PM
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#1
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Member
Join Date: Dec 2011
Location: SF, CA
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Causes of an intermittent P0171 ?
What else should I be looking at as the potential cause of an intermittent P0171 (the yellow check engine light goes on & off every couple of days)
I have a ScanGauge - anything I can check with it to help get to the bottom of this?
Supercharged
CA emissions (w/dual cats)
- I've cleaned the MAF
- Using a Toyota Paper Air Filter
- Replaced both the AF & O2 sensor (with Denso)
Thank you and Happy New Year
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1999 "Highlander" V6 4WD E-Locker || TRD Supercharger, URD 7th Injector, 2.2 Pulley || Toytec Aluma Series Boss Suspension, SPC A-Arms, Durobumps, Overland Endlinks || B&M Trans Cooler || 231mm Tundra Brakes, SS Brake Lines || 17" TRD Pro Wheels || BFG KO2 265/70R17-C || TRD Exhaust || 01-02 Tail Lights || Original Owner
Last edited by TRD 4RNR; 01-01-2022 at 12:33 AM.
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12-31-2021, 10:24 PM
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#2
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Join Date: Nov 2018
Location: San Jose, CA
Posts: 522
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Member
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Location: San Jose, CA
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Quote:
Originally Posted by TRD 4RNR
What else should I be looking at as the potential cause of an intermittent P0171 (the yellow check engine light goes on & off every couple of days)
- I've cleaned the MAF
- Using a Toyota Paper Air Filter
- Replaced both the AF & O2 sensor
(CA emissions w/ dual cats)
Thank you and Happy New Year
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Lean could mean a leak. Inspect your hoses for damage, and if you want, you can spray something flammable like carb cleaner around the various hoses listening for the RPM to change to try and track down the source of the leak.
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12-31-2021, 11:31 PM
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#3
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Join Date: Jun 2013
Location: Virginia
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The big throttle body hoses can/do crack and/or the clamps get loose over time.
If you haven't already, use only Denso sensors. Aftermarket ones often just
don't work. I chased this code, and it took longer because the replacement
non/Denso rear O2 sensor was off. Replaced it with the original eventually. My
problem turned out to be the front A/F sensor.
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'02 Limited 4x4 AT - Stock ~181k miles
Thundercloud aka metallic dirt
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12-31-2021, 11:40 PM
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#4
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You can use a smoke machine for the hoses to see if one is leaking. Very handy tool to have/use.
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2000 4Runner Limited 4x4 V6
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01-01-2022, 12:26 AM
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#5
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Quote:
Originally Posted by heat
The big throttle body hoses can/do crack and/or the clamps get loose over time.
If you haven't already, use only Denso sensors. Aftermarket ones often just
don't work. I chased this code, and it took longer because the replacement
non/Denso rear O2 sensor was off. Replaced it with the original eventually. My
problem turned out to be the front A/F sensor.
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I used Denso
I'll check for cracks and/or loose clamps.
Might be time for a smoke machine.
Thank you
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1999 "Highlander" V6 4WD E-Locker || TRD Supercharger, URD 7th Injector, 2.2 Pulley || Toytec Aluma Series Boss Suspension, SPC A-Arms, Durobumps, Overland Endlinks || B&M Trans Cooler || 231mm Tundra Brakes, SS Brake Lines || 17" TRD Pro Wheels || BFG KO2 265/70R17-C || TRD Exhaust || 01-02 Tail Lights || Original Owner
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01-01-2022, 12:57 PM
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#6
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Senior Member
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Here is the cause of an 0171 on mine, largest air intake 'hose' nearest intake had a crack that could only be seen if pulled apart just a hair yet the leak was there regardless, went OEM and smilin' since!
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2001 Limited 4WD - 346+K - SunfireRed\Thunder Cloud; - 265/75/16 Michelin A/T2s - Fat Pat's 1.5" BL - StopTech ANGLED rotors - In series 699 trans cooler, New Yota1 transmission, All new OEM suspension front to rear.
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01-01-2022, 08:28 PM
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#7
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Quote:
Originally Posted by jgue467
Here is the cause of an 0171 on mine, largest air intake 'hose' nearest intake had a crack that could only be seen if pulled apart just a hair yet the leak was there regardless, went OEM and smilin' since!
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I just did this over the weekend, along with the A/C idler pulley. What a world of difference it made in the power and sound. I was about to start troubleshooting a phantom miss at idle, but the Boot was the cause of all my issues!
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01-15-2022, 03:29 PM
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#8
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Member
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Join Date: Dec 2011
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Member
Join Date: Dec 2011
Location: SF, CA
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Quote:
Originally Posted by jgue467
Here is the cause of an 0171 on mine, largest air intake 'hose' nearest intake had a crack that could only be seen if pulled apart just a hair yet the leak was there regardless, went OEM and smilin' since!
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@ jgue467
I bought the part in your post and went to install it today and found the hole in the side to be much larger in the new one. Should I have ordered something different? Or do I need a different plug?
Thanks
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1999 "Highlander" V6 4WD E-Locker || TRD Supercharger, URD 7th Injector, 2.2 Pulley || Toytec Aluma Series Boss Suspension, SPC A-Arms, Durobumps, Overland Endlinks || B&M Trans Cooler || 231mm Tundra Brakes, SS Brake Lines || 17" TRD Pro Wheels || BFG KO2 265/70R17-C || TRD Exhaust || 01-02 Tail Lights || Original Owner
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01-15-2022, 04:08 PM
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#9
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Quote:
Originally Posted by TRD 4RNR
@ jgue467
I bought the part in your post and went to install it today and found the hole in the side to be much larger in the new one. Should I have ordered something different? Or do I need a different plug?
Thanks
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They have different air cleaner hoses for build date.
17882-62010 5VZFE..VZN18* (07/1998 - 07/2000)
17882-62020 5VZFE..VZN18* (08/2000 - )
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