P0174 System Too Lean (Bank 2)
Get it checked soon
The computer on bank 2 has to add much more fuel than normal. If P0171 is also set, look for one cause both banks share. If P0174 is alone, look at the bank 2 side of the intake. Drivable for now; fix it within weeks.
- Safe to drive?
- Yes, but fix it within weeks
- Typical cost at a shop
- $124-$1,513 RepairPal national averages, parts and labor
- Emissions test
- Yes, while the check engine light is on, most OBD emissions tests fail the car.
- Carmaker bulletins
- 2 notes with links
What it means
This is the same fault as P0171, on the other side of the engine. Bank 2 is the row of cylinders that does not contain cylinder 1, so P0174 only appears on V6, V8 and flat engines. The oxygen sensor on bank 2 sees too much oxygen, the computer adds fuel, and the correction has reached its limit.
The technical version
The fuel system monitor compares the learned (long-term) and fast (short-term) fuel trim on each bank against a lean limit. P0174 sets when bank 2's total correction stays past that limit, usually on two drives. The pair P0171 plus P0174 is one of the most useful patterns in OBD: it rules out anything that lives on only one side.
Official name: Fuel Trim too Lean (Bank 2).
Symptoms
- Often only the check engine light.
- Rough idle or hesitation.
- A hiss from a vacuum leak.
- Misfire codes later if it stays lean.
Causes, most likely first
| Cause | How likely | How to tell |
|---|---|---|
| With P0171 also set: a shared cause such as a dirty MAF sensor, low fuel pressure or a large vacuum leak | most common | Both banks show high positive long-term trim, often by a similar amount. |
| Alone: an intake manifold gasket or hose leak on the bank 2 side | common | Bank 2 trim is high, bank 1 is near 0%, and it is worst at idle. |
| A PCV hose or valve leak | common | Trims improve with revs; the hose is cracked or soft. |
| Injector trouble on bank 2 | less common | Bank 2 trim high under load too; misfire counts on bank 2 cylinders. |
| An exhaust leak near the bank 2 front oxygen sensor | rare | Ticking at the manifold on a cold start. |
How likely is our ranking from repair data and common practice, not a published rate.
What the live data shows
Compare long-term fuel trim on the two banks. Both high: shared cause. Bank 2 high and bank 1 near 0%: something on the bank 2 side. Then compare idle with 2,500 rpm: worst at idle points to a vacuum leak; worst under load points to fuel delivery or the MAF sensor.
What to check first, in order
-
Read codes and note whether P0171 is set too.
It tells you whether to look for one shared cause or one side.
What the data shows: Freeze frame rpm and load show where it set.
Cost: no cost if you have a scanner
-
Compare both banks' fuel trims at idle and 2,500 rpm.
It splits shared from one-sided causes, and leaks from fuel or MAF.
What the data shows: Add short-term and long-term trim for each bank.
Cost: no cost if you have a scanner
-
Clean the MAF sensor if both banks are lean.
Cheap, and a dirty MAF leans out both banks.
What the data shows: Trims should move toward 0% after cleaning.
Cost: a can of MAF cleaner
-
Inspect and smoke-test the bank 2 intake side.
Gaskets and hoses on that side are the usual one-sided cause.
What the data shows: Short-term trim drops when you block a leak.
Cost: $683-$834 at a shop (Intake manifold gasket replacement, RepairPal)
-
Test fuel pressure under load.
Low pressure leans both banks, worst under load.
What the data shows: Fuel rail pressure, where the car reports it.
Cost: $1,344-$1,513 at a shop (Fuel pump replacement, RepairPal)
Is it safe to drive?
Get it checked soon
Yes, but fix it within weeks. The engine runs on a fuel correction that is at its limit.
Drivable for now. Expect rough idle or hesitation to develop, and do not let it run for months: long, hard driving on a lean mixture is hard on an engine. If P0171 is set as well, check the simple shared causes first.
Stop driving and get help if
- The check engine light flashes.
- The engine misfires or stalls.
- You smell raw fuel.
What it costs
| Repair | Typical cost |
|---|---|
| PCV valve replacementRepairPal, updated September 3, 2026 | $124-$173 |
| Check engine light diagnosis (shop)RepairPal, updated September 3, 2026 | $125-$183 |
| Fuel filter replacementRepairPal, updated September 3, 2026 | $258-$322 |
| Mass airflow (MAF) sensor replacementRepairPal, updated September 3, 2026 | $274-$381 |
| Intake manifold gasket replacementRepairPal, updated September 3, 2026 | $683-$834 |
| Fuel pump replacementRepairPal, updated September 3, 2026 | $1,344-$1,513 |
National averages for the full job at a shop, parts and labor, from RepairPal (updated September 3, 2026). Your price depends on the car and the area. Many of the first checks on this page cost nothing with a scanner. CarMD found the average check engine repair in 2025 was $554, from more than 39 million US vehicles. MAF sensor replacement was CarMD's number 4 check engine repair in 2025, at an average of $346. CarMD averages come from a different method (repairs reported by its users), so they can sit below RepairPal's shop estimates.
Sources for the notes: CarMD 2026 Vehicle Health Index (press release, April 22, 2026).
Can I clear it? Will it come back?
After the repair, clear the code and watch bank 2 long-term trim over a few drives. It should settle near 0%.
Will it fail an emissions test?
Yes, while the check engine light is on, most OBD emissions tests fail the car.
Carmaker notes
Service bulletins and warranty extensions that name this code. Ask a dealer to check your VIN.
-
Toyota 2022-2023 Tundra and Tundra hybrid, 2023 Sequoia hybrid
Toyota bulletin T-SB-0030-23 (June 2023): P0174 with P0430. The fix replaces the left No. 2 fuel delivery pipe and the left catalytic converter.
Toyota T-SB-0030-23 via NHTSA static.nhtsa.gov
-
Toyota 2009-2018 Sequoia and 2009-2019 Tundra with the 3UR-FBE flex-fuel engine
Toyota bulletin T-SB-0166-19 (December 2019) covers P0171 and P0174 when the engine estimates more alcohol in the fuel than there is.
Toyota T-SB-0166-19 via NHTSA static.nhtsa.gov
Related codes
Also related, no guide yet: P0175, P0172.
How Obie handles P0174
Obie compares the fuel trims on both banks at idle and at higher revs, and tells you whether to look for one shared cause or a leak on one side. Obie is part of ScanMyCar Pro. Codes and live sensors are free.
Questions people ask
What causes P0171 and P0174 together?
Something both banks share: a dirty MAF sensor, low fuel pressure or a large vacuum leak such as a PCV hose.
Which side is bank 2?
The side of the engine without cylinder 1. Your repair manual shows cylinder 1.
Can I drive with P0174?
Yes, for a short time. Fix it within weeks, and sooner if the engine misfires.
Sources
- RepairPal: P0174 code page repairpal.com
- RepairPal: PCV valve replacement (updated September 3, 2026) repairpal.com
- RepairPal: Check engine light diagnosis (shop) (updated September 3, 2026) repairpal.com
- RepairPal: Fuel filter replacement (updated September 3, 2026) repairpal.com
- RepairPal: Mass airflow (MAF) sensor replacement (updated September 3, 2026) repairpal.com
- RepairPal: Intake manifold gasket replacement (updated September 3, 2026) repairpal.com
- RepairPal: Fuel pump replacement (updated September 3, 2026) repairpal.com
- CarMD 2026 Vehicle Health Index (press release, April 22, 2026) prnewswire.com
- Toyota T-SB-0030-23 via NHTSA static.nhtsa.gov
- Toyota T-SB-0166-19 via NHTSA static.nhtsa.gov
- Texas DPS emissions testing FAQ dps.texas.gov
- Arizona myazcar.com: OBD and the check engine light myazcar.com
A guide, not a diagnosis. This page describes what P0174 generally means across OBD2 cars. What is actually wrong with your car depends on its live data and its history, and any repair decision deserves a proper diagnosis, whether that is you with a scanner or a professional with a lift.
