P0171 on Toyota: Common Causes and Fixes

What does P0171 mean on a Toyota?

P0171 means the engine computer has added as much fuel as it is allowed on bank 1, and the exhaust still reads lean. Bank 1 is the side with cylinder 1; on four-cylinder Toyotas such as the Corolla, Camry four-cylinder or RAV4, there is only one bank. ALLDATA DIY sums up a lean code as too much air, not enough fuel, or both ^[2].

The code definition is the same on every make. What changes from one maker to another is the list of known patterns behind it. Our main P0171 guide explains the general mechanism, fuel trims and the full list of causes. This page focuses on what Toyota itself has published.

What makes P0171 different on Toyota?

Toyota has published a service bulletin that names P0171 on a specific group of trucks. Bulletin T-SB-0166-19 (revision 1, January 2020), titled "Extended Crank and/or MIL ON With DTC P0171, P0174, P0172, P0175, P1604 (Flex-Fuel)," applies to:

• 2009 to 2019 Tundra with the 3UR-FBE engine
• 2009 to 2018 Sequoia with the 3UR-FBE engine

The 3UR-FBE is the flex-fuel version of Toyota's 5.7L V8, built to run on gasoline or E85. Toyota says some of these trucks may crank longer than normal before starting and turn on the check engine light with lean codes (P0171, P0174), rich codes (P0172, P0175) or P1604, a startability code. Toyota adds that dealer scan tool data may show negative fuel trims and an estimated fuel alcohol content that is higher than what is actually in the tank ^[1]. The full bulletin is public on NHTSA's document server, static.nhtsa.gov.

In plain terms, a flex-fuel engine has to estimate how much ethanol is in the tank so it can adjust fuel delivery. If that estimate is off, the computer's fuel corrections are off too, and fuel trim codes can follow.

The bulletin's repair has four parts: reprogram the engine computer with updated software, replace the fuel pump assembly (the fuel suction tube with pump and gauge), reset the fuel alcohol learned value, and add fuel. It replaced an earlier bulletin, T-SB-0058-13. Toyota states that this repair is covered under the Toyota Federal Emission Warranty for 96 months or 80,000 miles, whichever comes first, from the in-service date, and only for the condition the bulletin describes.

Does the Toyota bulletin apply to my truck?

Only if your truck matches all three: it is a Tundra (2009 to 2019) or Sequoia (2009 to 2018), it has the 5.7L V8, and that V8 is the 3UR-FBE flex-fuel version. Not every 5.7L truck is flex-fuel. The bulletin also lists specific vehicle descriptor codes (part of the VIN) for each model.

The easiest way to be sure is to ask a Toyota dealer to check your VIN against open bulletins. You can also decode the VIN with our VIN decoder to confirm the model year and engine, and your owner's manual will say whether the truck is approved for E85.

If your Toyota is not on that list, the bulletin does not apply, and P0171 should be diagnosed like any other lean code. That includes most Toyota cars and crossovers.

Is it safe to drive a Toyota with P0171?

Usually yes for a short time, but get it checked soon. Carista lists rough idle, possible stalling, hesitation, reduced power and idle misfires as typical P0171 symptoms ^[3]. On the flex-fuel trucks in the bulletin, the main complaint is a long crank before the engine starts.

Pull over when it is safe and stop driving if the check engine light starts flashing or the engine shakes. The California Air Resources Board explains that a blinking light means a malfunction that could be damaging the catalytic converter ^[4]. Our guide to a flashing check engine light covers what to do next.

What should you check on a Toyota with P0171?

Start with a scanner, then the cheap checks. Our guide on how to use an OBD2 scanner explains freeze frame and live data.

1. Read every code and the freeze frame. On a V8, note whether P0174 is set too. Both banks lean points to a shared cause. On a flex-fuel truck, also note any P1604 or rich codes, which match the bulletin's pattern.
2. Check fuel trims. Carista notes that short and long term trims above +10% help confirm a lean condition. Compare idle with about 2,500 rpm: trims that drop at higher rpm suggest a vacuum leak.
3. Visual check. Look at the intake boot between the air box and throttle body, vacuum and PCV hoses, the oil filler cap and the dipstick seal.
4. Air filter and MAF sensor. Look for a dirty filter or debris on the sensor.
5. Ask about bulletins. For a flex-fuel Tundra or Sequoia, ask the dealer about T-SB-0166-19 before paying for a fuel pump elsewhere. The bulletin's procedure needs Toyota's dealer scan tool to reset the fuel alcohol learned value.
6. Fuel pressure and smoke tests by a qualified technician, since fuel pressure work involves a pressurized system.
7. Oxygen sensor last. ALLDATA DIY warns that the sensor is often just reporting a real lean condition.

	Generic P0171 causes	Toyota flex-fuel bulletin (T-SB-0166-19)
Which vehicles	Any make or model	2009 to 2019 Tundra, 2009 to 2018 Sequoia, 3UR-FBE only
Typical complaint	Rough idle, hesitation, weak power	Long crank before starting, check engine light
Codes	P0171, often with P0174	P0171, P0174, P0172, P0175 and/or P1604
Main cause	Air leak, MAF sensor, low fuel pressure	Fuel alcohol estimate off, per the bulletin
Fix	Repair the leak or failed part	ECM update, fuel pump assembly, alcohol learn reset
Who pays	Owner, unless under warranty	Toyota Federal Emission Warranty, 96 months or 80,000 miles

How do you fix P0171 on a Toyota, and what does it cost?

For trucks covered by T-SB-0166-19, the fix is the dealer procedure above, and Toyota's warranty statement covers it within 96 months or 80,000 miles for that condition. Outside that window, the cost depends on the dealer's labor and parts; the bulletin's warranty labor time is 2.2 hours. We do not quote a dollar figure, because we found no reliable public price for this job as of November 2026.

For every other Toyota, the fix is whatever the diagnosis finds, from a cheap hose or intake boot to a MAF sensor or fuel pump. Cost depends on the part, how much has to come apart and the shop's diagnostic time.

After a repair, clear the code and drive normally. Clearing a code does not fix anything, and it resets the readiness monitors. California requires all readiness monitors to be set to pass Smog Check, and they complete through normal driving or a drive cycle ^[5].