P0174 on Toyota: How to Diagnose & Fix
System Too Lean (Bank 2)
6 Toyota models · 6 documented issues · 3 critical · $300-$1,400 repair
P0174 on Toyota by model: symptoms, diagnosis and fix
The water pump on the 3.5L 2GR-FE fails prematurely between 80,000-120,000 miles, developing a coolant leak from the weep hole or gasket surface. If not addressed, complete pump failure causes overheating and potential head gasket damage.
Common Symptoms
- Coolant leak from front/center of engine
- Coolant level dropping
- Overheating at idle or low speeds
- Whining noise from water pump area
- Sweet coolant smell
How to Fix
Replace water pump (Toyota 16100-09442, which supersedes 16100-39455/16100-39456, or Aisin WPT-803). Replace the thermostat at the same time (confirm the 2GR-FE thermostat part number by VIN). Use Toyota SLLC or equivalent coolant. The pump is driven by the serpentine belt, so inspect the belt and tensioner during replacement.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Aisin WPT-803 mechanical water pump
confirmed mechanical pump leak or bearing-failure branch Fitment/availability: 2005-2018 Toyota Avalon 3.5L 2GR-FE mechanical water-pump application; confirm VIN and production date Fitment/availability: direct product page and cart cont…
- Genuine Toyota 90916-A3002 thermostat
thermostat branch when due, diagnosed or deliberately replaced during overlapping cooling-system service Fitment/availability: 2005-2018 Toyota Avalon 3.5L; replaces 90916-03133, 90916-03140 and 90916-A3001; confirm VIN Fitment/availabil…
- Toyota 00272-SLLC2 50/50 Super Long Life Coolant
correct coolant for refill and bleed after mechanical pump service Fitment/availability: Toyota Super Long Life Coolant maintenance/refill branch; verify total system quantity and never mix incompatible coolant Fitment/availability: Add …
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Sources for this issue (2)
The 2.4L FA24 boxer engine in the GR86 consumes oil more than expected, particularly when driven hard on track. Consumption of 1 quart per 2,000-3,000 miles is common. The horizontal cylinder layout and high-RPM operation contribute to oil consumption past the piston rings.
Common Symptoms
- Oil level drops between changes
- Low oil pressure warning after spirited driving
- Need to add oil every 2,000-3,000 miles
- Blue smoke on cold start after sitting
How to Fix
Monitor oil level closely, especially before and after track days. Use Subaru/Toyota 0W-20 synthetic oil and check every 1,000 miles. Keep oil level at full mark. Some owners use 5W-30 for track use (not recommended for daily driving under warranty). Carry a quart of oil in the trunk. If consumption exceeds 1 qt per 1,200 miles, request an oil consumption test at the dealer.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Mobil 1 Extended Performance full-synthetic 0W-20 motor oil, 1 quart
one-quart top-up container for documented low oil level—not a treatment for the cause of abnormal consumption Fitment/availability: Universal SAE 0W-20 full-synthetic oil carrying the API/ILSAC certifications shown on the live listing; u…
- Toyota 90915-YZZS1 genuine engine oil filter
correct-fit maintenance filter when an oil change is due; not a repair for ring, seal, PCV or leakage faults Fitment/availability: 2022-2025 Toyota GR86 2.4L FA24 applications per the live catalog; replaces SU003-00311 and SU003-08412; c…
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The Denso-built low-pressure (in-tank) fuel pump can fail without warning. The pump impeller was molded from a lower-density resin that absorbs fuel over time, swells, and binds against the pump housing, stopping the pump. This cuts fuel delivery and causes the engine to stall, often at speed. It was covered under NHTSA recall 20V-682 (Toyota 20TA02), an expansion of 20V-012, affecting roughly 2017-2020 Siennas alongside many other Toyota/Lexus models.
Common Symptoms
- Engine stalls or dies while driving, sometimes at highway speed
- Long crank / hard start, especially when warm
- Rough running, sputtering, or hesitation before stalling
- Check engine light with lean or fuel-trim codes in some cases
- Whining or no sound from fuel tank at key-on
How to Fix
Have the vehicle checked against recall 20V-682/20TA02 at any Toyota dealer; the remedy is free replacement of the fuel pump assembly with the redesigned (higher-density impeller) unit. Owners of unrepaired vehicles experiencing hard starts, rough running, or a sudden stall with no DTC for misfire should suspect the pump. Replacement of the full fuel pump/sender assembly out of warranty runs roughly $600-$1,000.
Call to confirm they can assess your vehicle and perform the stated work. Search results do not confirm qualification, eligibility or coverage.
Sources for this issue (3)
The cast-iron exhaust manifolds on the 4.0L 1GR-FE V6 are prone to cracking from repeated heat cycling, with thin webs near the firewall failing first. This is a distinct mechanical failure from the well-known injector 'Taco Tick' and the secondary-air-injection problem. A cracked manifold produces a loud ticking or tapping that is worst on a cold start and may quiet as the engine warms, often with a faint exhaust smell at the firewall. Beyond the noise, the upstream exhaust leak skews the air/fuel reading, ruins fuel economy, can trip lean/misfire and oxygen-sensor codes, can cause a smog-test failure, and over time can cook the catalytic converter and exhaust valves. Owners commonly find the driver-side (left bank) manifold cracked first because of its packaging near the firewall.
Common Symptoms
- Loud ticking or tapping noise worst on cold start
- Noise partially quiets as engine warms up
- Faint exhaust smell near firewall
- Drop in fuel economy
- Louder under light acceleration/load
- Possible lean/oxygen-sensor or misfire codes
- Smog/emissions test failure
How to Fix
Confirm the source with a cold-start listen and a smoke/soap test at the manifold-to-head flange and along the manifold casting (a cracked manifold gets louder under light load/acceleration, unlike the harmless injector tick). Replace the cracked manifold(s) with OEM or quality aftermarket units and new manifold gaskets and hardware; many shops replace both banks while access is open. Use new exhaust manifold-to-head nuts/studs and the OEM gasket to prevent a repeat leak. Replacing only the gasket will not cure an actual casting crack.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Toyota 17150-0P100 genuine early driver-side manifold/catalyst
replace a confirmed cracked early-production left integrated manifold/catalyst Fitment/availability: Driver side, 2005-2008 Toyota Tacoma 4.0L 1GR-FE; supersedes 17150-0P010/0P070 and requires VIN/emissions confirmation Fitment/availabil…
- Toyota 17140-0P100 genuine early passenger-side manifold/catalyst
replace a confirmed cracked early-production right integrated manifold/catalyst Fitment/availability: Passenger side, early 2005-2009 Toyota Tacoma 4.0L catalog branch; supersedes 17140-0P070 and requires VIN/build-date/emissions confirm…
- Toyota 17150-0P140 genuine 2009-2011 driver-side manifold/catalyst
replace a confirmed cracked middle-production left integrated manifold/catalyst Fitment/availability: Driver side, principally 2009-2011 Tacoma 4.0L production branch; listing notes Mexico specification, so VIN/build-date and market conf…
- Toyota 17140-0P140 genuine 2009-2011 passenger-side manifold/catalyst
source the exact middle-production right integrated manifold/catalyst through a Toyota dealer after the side and fitment are confirmed Fitment/availability: Passenger side 2009-2011 Tacoma 4.0L production branch; confirm VIN, build date,…
- Toyota 17150-0P230 genuine 2012-2015 driver-side manifold/catalyst
replace a confirmed cracked late-production left integrated manifold/catalyst Fitment/availability: Driver side, 2012-2015 Toyota Tacoma 4.0L 1GR-FE; confirm VIN and emissions configuration Fitment/availability: Ships in 1-2 business day…
- Toyota 17140-0P230 genuine 2012-2015 passenger-side manifold/catalyst
replace a confirmed cracked late-production right integrated manifold/catalyst Fitment/availability: Passenger side, 2012-2015 Toyota Tacoma 4.0L 1GR-FE; select 17140-0P230 and confirm VIN/emissions configuration Fitment/availability: Sh…
- Toyota 17173-0P010 genuine middle-branch manifold-to-head gasket
install a new manifold-to-head gasket whenever the matching middle-production manifold is removed Fitment/availability: 2009-2011 Tacoma 1GR-FE catalog branch, used at either bank; verify VIN and quantity for the side(s) removed Fitment/…
- Toyota 17173-31040 genuine late-branch manifold-to-head gasket
install a new manifold-to-head gasket whenever the matching late-production manifold is removed Fitment/availability: 2012-2015 Tacoma 1GR-FE late manifold branch, used at either bank; confirm VIN and quantity Fitment/availability: Add t…
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Sources for this issue (3)
Certain Highlanders are part of Toyota's large Denso low-pressure fuel pump recall (NHTSA 20V-012). The pump's impeller can absorb excessive fuel and deform, interfering with the pump body and causing the pump to fail. This leads to rough running, hard starting, and engine stalling — potentially at speed and without warning — creating a crash risk. The defect spans many Toyota/Lexus models; the 2018-2019 Highlander was named in the original campaign, and 2017-2019 Highlanders were added in the 20V-682 expansion.
Common Symptoms
- Engine stalls while driving, sometimes at speed
- Long crank / hard starting
- Rough idle or hesitation
- Illuminated check engine light
- Engine fails to restart after stalling
- Fuel system warning indicators
How to Fix
Under recall 20V-012 (and related expansions), Toyota dealers replace the low-pressure fuel pump assembly with an improved-impeller unit free of charge. Owners should run their VIN at nhtsa.gov or contact Toyota; vehicles showing stalling/hard-start symptoms before the pump is replaced should be inspected promptly.
Sources for this issue (4)
Tundras built with certain Denso low-pressure (in-tank) fuel pumps have a defectively designed plastic impeller that can absorb fuel, swell/deform, and strike the pump housing — causing the pump to seize. The result is hard starting, rough running, illuminated warning lights, and engine stalling, including potentially at speed, which is a crash risk. Toyota recalled millions of Toyota/Lexus vehicles (pump part numbers beginning 23220/23221) starting January 2020 and expanded it repeatedly; affected Tundra model years are 2018-2020 (recalls 20V-012 and 20V-682, plus Customer Support Program 23TE05). A class-action settlement created a Customer Support Program extending coverage to 15 years from original sale for fuel-pump repairs.
Common Symptoms
- Engine stalls while driving or at idle
- Long crank / hard starting
- Rough running or hesitation
- Check engine light
- Whining or no fuel-pump prime noise
- Fuel-related warning lights
How to Fix
Covered under Toyota recall / Customer Support Program — dealer replaces the low-pressure fuel pump with an improved-impeller design at no charge. Verify the VIN on the NHTSA or Toyota recall site. Out-of-coverage replacement involves dropping or accessing the in-tank pump assembly. Reimbursement may be available for prior out-of-pocket repairs.
Sources for this issue (6)
- NHTSA Recall 20V-012: Fuel Pump May Fail (2018-2019 Tundra)nhtsa
- NHTSA Recall 20V-682: Fuel Pump May Fail (2019-2020 Tundra)nhtsa
- Toyota Customer Support Program 23TE05 - Denso Low Pressure Fuel Pump Class Action Settlementtsb
- Toyota Tundra Fuel Pump Recall - Asbury Autorecall
- Fuel pump recall...more Toyotas added to include 18-20 Tundraforum
- Toyota Fuel Pump Recall Isn't Adequate, Alleges Lawsuit - CarComplaintsarticle
P0174 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0174 mean on a Toyota?
P0174 stands for "System Too Lean (Bank 2)." P0174 means the engine computer detected that the air-fuel mixture on Bank 2 (the side of the engine that does not contain cylinder 1) is running too lean — too much air relative to fuel. The computer monitors this through the oxygen/air-fuel sensors and fuel trims; when it has to add a large amount of extra fuel to compensate and still can't reach the target, it flags the mixture as too lean. A lean condition can cause rough idle, hesitation, or misfires, and over time can raise combustion temperatures. Because it's Bank 2 specific, an unmetered air leak on that bank or a fuel delivery shortfall is typical. On Toyota it is documented across 6 models: Avalon, GR86, Sienna, Tacoma, Highlander, Tundra.
What are the most common causes of P0174?
The most common causes of P0174 are: Vacuum or intake air leak (hoses, gaskets, PCV), Dirty or failing mass airflow (MAF) sensor, Weak fuel pump or restricted fuel filter (low fuel pressure), Clogged or underperforming fuel injectors, Leaking intake manifold or throttle body gasket, Faulty or contaminated oxygen / air-fuel sensor, Exhaust leak upstream of the oxygen sensor, Stuck-open EGR valve. The specific cause varies by vehicle.
How much does it cost to fix P0174 on a Toyota?
Published repair estimates on Toyota range from $300 to $1,400 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.