--- title: P0172 and Your Nevada Smog Check | Xpress Smog Check Center url: https://xpresssmogcenter.com/codes/p0172/ 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/) - P0172 # P0172 and your Nevada smog check P0172 means the engine computer has pulled as much fuel out of the bank 1 mixture as it is allowed to and the exhaust still shows too little oxygen, so the engine is running rich. The code turns on the check engine light, which is an automatic smog check failure for a 1996 or newer light-duty vehicle in Nevada. 4.7 stars from 550 Google reviews of the two Reno Xpress Oil & Lube Centers Rich is the opposite of lean: too much fuel for the air coming in. Drivers sometimes notice it as a fuel smell, black soot at the tailpipe or a drop in mileage, and sometimes notice nothing. A rich engine is hard on the catalytic converter over time, which is one more reason to handle P0172 before it turns into a second, more expensive code. ## At a glance - The SAE J2012 definition is System too rich (bank 1). - Rich means the computer cannot trim enough fuel to balance the mixture on bank 1. - A lit lamp fails the Nevada OBD test; a rich condition left alone can also wear on the converter. - Gasoline vehicles may not give off visible smoke anywhere in Nevada, according to the DMV. ## What rich means SAE J2012 is the standard that fixes the meaning of generic OBD II codes. Its definition of P0172 is: System too rich (bank 1). The engine computer reads the front oxygen sensor and keeps trimming fuel to hold the mixture steady. When it has trimmed fuel as far as its limit and bank 1 still reads rich, it stores P0172. On a four-cylinder engine bank 1 is the whole engine. On a V engine it is the side with cylinder 1, and the lean codes for the two sides are [P0171](https://xpresssmogcenter.com/codes/p0171/) and [P0174](https://xpresssmogcenter.com/codes/p0174/). ## Why the computer cares Unburned fuel is exactly what emission controls are meant to keep out of the air. Extra fuel also reaches the catalytic converter, which has to burn it off, and over time that heat and residue can shorten the converter's life. A converter that falls behind sets its own code, [P0420](https://xpresssmogcenter.com/codes/p0420/), so a rich condition is worth dealing with early. ## One rule at the smog check A 1996 or newer car or light truck with its check engine lamp on fails Nevada's OBD inspection. That is the whole rule, and it applies to P0172 the same as any code. Two related DMV points are worth knowing. First, the failed report is not wasted: it is the legal record that opens the waiver path and supports a ten-day movement permit at reduced cost if the registration has expired. Second, gasoline vehicles must not emit visible smoke anywhere in Nevada, and a smoking vehicle can be cited or ordered to test; a smoking vehicle is also not eligible for a waiver. ## Common causes a repair shop checks Xpress Smog Check Center tests vehicles; diagnosing a rich mixture is a repair shop's job, and the DMV recommends a 2G licensed authorized station for emissions repairs. Common causes a repair shop checks include: - A leaking or sticking fuel injector. - Fuel pressure that runs too high. - An air flow sensor that reads high, or a badly restricted air filter. - A front oxygen sensor giving a false rich reading. - A purge valve letting fuel vapor into the engine at the wrong time. ## What to do before you come in Look at the timing. A passing test is good for 90 days, and testing early in your renewal window leaves time for a repair. If the car has just been repaired, wait until it has been driven up to a week in mixed conditions; clearing codes right before a test gets the vehicle rejected as not ready. If the repair involves an expensive emission component, call the dealer before paying to ask about federal emissions warranty coverage or a recall, which can cover some components up to 8 years or 80,000 miles. Pull any insurance tracker or monitoring device out of the diagnostic port before you arrive. The DMV requires technicians to fail a vehicle with one plugged in. ## After a failed test The order in Washoe County is fail, repair, retest. If the lamp is still lit after repairs, the vehicle may qualify for a waiver with receipts showing at least $200 in related parts and labor at a 2G station, or at least $200 in related parts the owner bought within 14 days after the initial test. Repairs before the first failed test do not count. The [repair and retest page](https://xpresssmogcenter.com/smog-check/repair-and-retest/) has the next steps. ### Sources - [dmv.nv.gov/emission_obd.htm](https://dmv.nv.gov/emission_obd.htm) (Nevada DMV OBD page: lamp on is a fail, flashing light, cleared codes, 8 years / 80,000 miles; read 11/3/26) - [dmv.nv.gov/emission.htm](https://dmv.nv.gov/emission.htm) (Nevada DMV: no visible smoke from gasoline vehicles, smoking vehicles not waiver eligible; 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/p0172](https://www.obd-codes.com/p0172) (public OBD II code reference: P0172 system too rich, bank 1; read 11/3/26) ### P0172, the generic definition System too rich (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/) - [P0171 and your Nevada smog check](https://xpresssmogcenter.com/codes/p0171/) - [P0420 and your Nevada smog check](https://xpresssmogcenter.com/codes/p0420/) - [Smoking vehicles and visible exhaust](https://xpresssmogcenter.com/faq/smoking-vehicles/) - [Repair and retest](https://xpresssmogcenter.com/smog-check/repair-and-retest/) 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 [P0171 System too lean (bank 1) Learn more](https://xpresssmogcenter.com/codes/p0171/)[P0174 System too lean (bank 2) Learn more](https://xpresssmogcenter.com/codes/p0174/) ## 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/) ## P0172 questions Still have a question? Call either Reno location or just drive in; there is no appointment to make. ### My car smells like gas and shows P0172. Should I drive it in? A strong fuel smell is a reason to have a repair shop look at the car first. If the check engine light is flashing, the DMV says to slow down or stop driving and get service right away. ### Can a rich code damage anything else? Running rich for a long time can wear on the catalytic converter. That is why the code is worth handling soon, not just before the next test. ### Does P0172 fail the test even with no smoke? Yes. On a 1996 or newer light-duty vehicle, the lit lamp alone is a fail.