--- title: P0171 and Your Nevada Smog Check | Xpress Smog Check Center url: https://xpresssmogcenter.com/codes/p0171/ business: Xpress Smog Check Center (Located inside Xpress Oil & Lube Center) locations: Reno Northwest: 6100 Mae Anne Ave, Reno, NV 89523, (775) 787-1000, Mon-Fri 8 am-5 pm, Sat 8 am-4 pm, Sun closed; Reno South: 4993 Longley Ln, Reno, NV 89502, (775) 828-6996, Mon-Fri 8 am-5 pm, Sat 8 am-3 pm, Sun closed type: Nevada smog check (vehicle emissions inspection), drive in, no appointment --- Located inside Xpress Oil & Lube Center - Smog check at two Reno locations - Oil change in the same visit - No appointment needed [Xpress Oil & Lube](https://xpressoilandlube.com/) - [Home](https://xpresssmogcenter.com/) - [Codes](https://xpresssmogcenter.com/codes/) - P0171 # P0171 and your Nevada smog check P0171 means the engine computer has reached the limit of how much extra fuel it can add to bank 1 and the mixture is still lean, with more air than the fuel can match. The code lights the check engine lamp, and a lit lamp fails a 1996 or newer light-duty vehicle at a Nevada smog check. 4.7 stars from 550 Google reviews of the two Reno Xpress Oil & Lube Centers An engine runs best on a narrow balance of air and fuel, and the computer adjusts that balance many times a second. P0171 is what it reports when it has adjusted as far as it is allowed and still cannot get bank 1 back to balance. The car may hesitate, idle rough or feel completely normal. For the smog check, only the lamp counts. ## At a glance - SAE J2012 defines P0171 as System too lean (bank 1). - Lean means the computer measured more air than the fuel being delivered can balance. - A lit lamp from a fuel mixture code fails the Nevada OBD test like any other. - Clearing the code before the test resets the self-checks and brings a not ready rejection. ## Lean, in one paragraph The generic SAE J2012 wording is short: System too lean (bank 1). The computer reads the oxygen left in the exhaust and adds or trims fuel to keep the mixture where it should be; those corrections are called fuel trim. When it has to keep adding fuel to bank 1 and reaches its programmed limit, it decides the system is too lean and sets P0171. Bank 1 is the side of the engine with cylinder 1, and on a four-cylinder engine it is the only bank. If both sides of a V engine are lean, [P0174](https://xpresssmogcenter.com/codes/p0174/) often appears with it. ## What it does to emissions A mixture the computer cannot correct is a mixture it can no longer control, and the oxygen sensors and catalytic converter are designed around a controlled one. OBD II was built to flag faults that affect emissions, so it stores P0171 and lights the lamp. The Nevada DMV's general point applies: a car with the lamp on is likely wasting fuel and polluting, even if it drives well. ## Bringing a P0171 car to a Reno test Here the rule is brief. A 1996 or newer light-duty vehicle with the check engine lamp on fails Nevada's OBD test. A lean code earns no special treatment, and the result goes to the DMV with the rest. The DMV advises testing anyway, because the failed report is a legal record of why the vehicle fails. It is the first page of the waiver file if repairs get costly, and it supports a ten-day movement permit at reduced cost if your registration has run out. Spending on repairs before that report exists does not count toward a waiver. ## Common causes a repair shop checks Xpress Smog Check Center tests vehicles. For the cause, see a repair shop; the DMV recommends a 2G licensed authorized station for emissions repairs. Common causes a repair shop checks for a lean bank 1 include: - Vacuum leaks: cracked hoses or intake gaskets that let in air the computer did not measure. - An air flow sensor that reads low. - Weak fuel delivery, such as a tired fuel pump, a clogged filter or a dirty injector. - An exhaust leak ahead of the front oxygen sensor that adds outside air to the reading. ## Before you drive in Do not clear the code to get the lamp off for the test. The DMV is direct about it: clearing codes right before a test is an automatic rejection, because the readiness monitors reset and have to run again. If a repair has just been made, plan for up to a week of mixed city and highway driving so the monitors can finish, then come in. Take any insurance tracker out of the diagnostic port first, since technicians must fail a vehicle with a device plugged in. If the repair involves an expensive emission component, ask the dealer whether federal emissions coverage, up to 8 years or 80,000 miles on some parts, or a recall applies. ## When the lamp will not stay off Fail, repair and pass a retest is the normal order. A 1996 or newer light-duty vehicle that still fails for a lit lamp after repairs may qualify for a Washoe County waiver. The receipts need to show at least $200 in related parts and labor at a 2G station, or at least $200 in related parts bought by the owner within 14 days after the initial test. See our [waiver page](https://xpresssmogcenter.com/smog-check/smog-waiver/) for the lab visit. ### Sources - [dmv.nv.gov/emission_obd.htm](https://dmv.nv.gov/emission_obd.htm) (Nevada DMV OBD page: lamp on is a fail, test anyway, cleared codes rejected, OBD port devices, 8 years / 80,000 miles; read 11/3/26) - [dmv.nv.gov/regrenewal.htm](https://dmv.nv.gov/regrenewal.htm) (Nevada DMV renewal page: Washoe waiver receipts and $200 minimum; read 11/3/26) - [obd-codes.com/p0171](https://www.obd-codes.com/p0171) (public OBD II code reference: P0171 system too lean, bank 1; read 11/3/26) ### P0171, the generic definition System too lean (bank 1) The SAE J2012 code title. The same P0 code means the same thing on every 1996 and newer OBD II vehicle; the cause behind it differs car to car. ### Your location: Reno South - Call [(775) 828-6996](tel:+17758286996) Mon-Fri 8 am-5 pm, Sat 8 am-3 pm, Sun closed - Address 4993 Longley Ln, Reno, NV 89502 [Directions](https://www.google.com/maps/dir/?api=1&destination=4993+Longley+Ln%2C+Reno%2C+NV+89502&destination_place_id=ChIJc5xNCcI_mYARXjHn3y79iJw) ### Related - [Check engine codes](https://xpresssmogcenter.com/codes/) - [P0174 and your Nevada smog check](https://xpresssmogcenter.com/codes/p0174/) - [P0172 and your Nevada smog check](https://xpresssmogcenter.com/codes/p0172/) - [Check engine light and your smog check](https://xpresssmogcenter.com/smog-check/check-engine-light/) - [Rejected: not ready to test](https://xpresssmogcenter.com/smog-check/not-ready-rejected/) Located inside Xpress Oil & Lube Center Both smog check locations sit inside an Xpress Oil & Lube Center, the locally owned Reno drive-in that has served this town since 1983. Drive in, no appointment; get your oil changed in the same visit. [About us](https://xpresssmogcenter.com/about/) ## More fuel mixture codes [P0174 System too lean (bank 2) Learn more](https://xpresssmogcenter.com/codes/p0174/)[P0172 System too rich (bank 1) Learn more](https://xpresssmogcenter.com/codes/p0172/) ## If the light is on at your smog check [### Check engine light and your smog check Why a lit check engine light decides the test. Learn more](https://xpresssmogcenter.com/smog-check/check-engine-light/)[### Failed a smog check What the failed report means and the steps that follow. Learn more](https://xpresssmogcenter.com/smog-check/failed-smog-check/)[### Repair and retest Getting the repair done and coming back for the second test. Learn more](https://xpresssmogcenter.com/smog-check/repair-and-retest/)[### Rejected: not ready to test Why a car can be turned away without failing. Learn more](https://xpresssmogcenter.com/smog-check/not-ready-rejected/) ## P0171 questions Still have a question? Call either Reno location or just drive in; there is no appointment to make. ### Is a lean code the same as a misfire? No. A lean mixture can lead to misfires, and a repair shop may find both, but [P0300](https://xpresssmogcenter.com/codes/p0300/) is its own code with its own test. ### Will a fuel additive clear P0171? The lamp goes off when the cause is fixed and the computer confirms it. A repair shop can tell you what the cause is. ### I only see P0171, not P0174. Does that matter? It can help a repair shop narrow things down, since one bank lean and the other normal points toward something on that side. For the smog test, either code with the lamp lit is a fail.