--- title: Check Engine Codes and Your Nevada Smog Check | Xpress Smog url: https://xpresssmogcenter.com/codes/ 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 # Check engine codes and your Nevada smog check On a 1996 or newer light-duty vehicle, a lit check engine light is an automatic fail in a Nevada smog check, whatever code turned it on. These pages explain 24 common codes, grouped by the system that sets them, and what each one means for your test. 4.7 stars from 550 Google reviews of the two Reno Xpress Oil & Lube Centers A check engine code is a short label, a letter and four digits, that your car's computer stores when one of its self-checks finds a problem. The codes follow the SAE J2012 standard, so a P0420 means the same thing on every make. For the smog check, the code tells you why the lamp is on; the lamp is what decides the test. ## Why the lamp decides the test The Nevada DMV's OBD test reads the car's computer through the port under the dash. If the check engine light is on, the DMV says the vehicle fails. A flashing light is more serious: the DMV calls it a severe malfunction that can damage the catalytic converter, so slow down and get service. Clearing the code with a scan tool right before the test does not help. The computer's self-checks reset too, and the DMV rejects the car as not ready until they finish. ## How the code pages are grouped Each code has its own page, and the pages sit in seven groups by system: the catalytic converter, the evaporative emission (EVAP) system, fuel mixture, misfire and knock, oxygen sensors, air flow and idle, and a last group for temperature, cam timing and the transmission. ## Before you come in with a code Have a repair shop read the code and find the cause. Federal law covers some expensive emission components up to 8 years or 80,000 miles, so check with the dealer about coverage or a recall first. If the light came on suddenly, the DMV says a loose gas cap is a common cause. Testing with the light on still has a use: the failed report is the legal document that starts the repair, retest and waiver path, and the DMV does not count repair money spent before that first failed test toward a waiver. ## Catalytic converter [P0420 Catalyst system efficiency below threshold (bank 1) Learn more](https://xpresssmogcenter.com/codes/p0420/)[P0430 Catalyst system efficiency below threshold (bank 2) Learn more](https://xpresssmogcenter.com/codes/p0430/) ## Evaporative emission (EVAP) system [P0455 Evaporative emission system leak detected (large leak) Learn more](https://xpresssmogcenter.com/codes/p0455/)[P0442 Evaporative emission system leak detected (small leak) Learn more](https://xpresssmogcenter.com/codes/p0442/)[P0456 Evaporative emission system leak detected (very small leak) Learn more](https://xpresssmogcenter.com/codes/p0456/)[P0441 Evaporative emission system incorrect purge flow Learn more](https://xpresssmogcenter.com/codes/p0441/)[P0440 Evaporative emission system malfunction Learn more](https://xpresssmogcenter.com/codes/p0440/)[P0446 Evaporative emission system vent control circuit Learn more](https://xpresssmogcenter.com/codes/p0446/) ## Fuel mixture [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/)[P0172 System too rich (bank 1) Learn more](https://xpresssmogcenter.com/codes/p0172/) ## Misfire and knock [P0300 Random or multiple cylinder misfire detected Learn more](https://xpresssmogcenter.com/codes/p0300/)[P0325 Knock sensor 1 circuit (bank 1 or single sensor) Learn more](https://xpresssmogcenter.com/codes/p0325/) ## Oxygen sensors [P0135 O2 sensor heater circuit (bank 1, sensor 1) Learn more](https://xpresssmogcenter.com/codes/p0135/)[P0141 O2 sensor heater circuit (bank 1, sensor 2) Learn more](https://xpresssmogcenter.com/codes/p0141/)[P0133 O2 sensor circuit slow response (bank 1, sensor 1) Learn more](https://xpresssmogcenter.com/codes/p0133/) ## Air flow, EGR and idle [P0101 Mass or volume air flow (MAF) circuit range/performance Learn more](https://xpresssmogcenter.com/codes/p0101/)[P0113 Intake air temperature sensor 1 circuit high Learn more](https://xpresssmogcenter.com/codes/p0113/)[P0401 Exhaust gas recirculation (EGR) flow insufficient detected Learn more](https://xpresssmogcenter.com/codes/p0401/)[P0411 Secondary air injection system incorrect flow detected Learn more](https://xpresssmogcenter.com/codes/p0411/)[P0507 Idle air control system RPM higher than expected Learn more](https://xpresssmogcenter.com/codes/p0507/) ## Temperature, cam timing and transmission [P0128 Coolant temperature below thermostat regulating temperature Learn more](https://xpresssmogcenter.com/codes/p0128/)[P0010 Intake camshaft position actuator circuit (bank 1) Learn more](https://xpresssmogcenter.com/codes/p0010/)[P0700 Transmission control system malfunction (MIL request) Learn more](https://xpresssmogcenter.com/codes/p0700/) ## Check engine light help [### 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/)[### How the OBD smog test works The plug-in test for 1996 and newer cars and light trucks. Learn more](https://xpresssmogcenter.com/smog-check/obd-test/)[### Rejected: not ready to test Why a car can be turned away without failing. Learn more](https://xpresssmogcenter.com/smog-check/not-ready-rejected/)[### Failed a smog check What the failed report means and the steps that follow. Learn more](https://xpresssmogcenter.com/smog-check/failed-smog-check/) ## Questions people ask Still have a question? Call either Reno location or just drive in; there is no appointment to make. ### Will my car pass with the check engine light on? No. On a 1996 or newer light-duty vehicle, a lit check engine light is an automatic fail in Nevada. ### The light went off by itself. Can I test now? If nobody cleared the code, yes. If it was cleared with a tool, the DMV suggests up to a week of mixed city and highway driving first, or the car may be rejected as not ready.