P0113 and your Nevada smog check

The intake air temperature sensor tells the engine computer how cold or warm the incoming air is, a small detail that changes how much fuel the engine needs. P0113 is a circuit code, which usually points to electrical trouble rather than the air itself. Here is what that means, and how it plays out when you drive in for a smog check in Reno.

At a glance

• SAE J2012: Intake air temperature sensor 1 circuit high.
• Circuit high usually means the computer is seeing a signal like an unplugged sensor.
• A lit check engine light fails a 1996 or newer light-duty vehicle in Nevada.
• The federal emissions warranty may apply to some emission parts on newer vehicles.

Why high voltage reads as cold

In the SAE J2012 list, P0113 is "Intake air temperature sensor 1 circuit high." Most of these sensors are thermistors: their resistance drops as the air warms. The computer sends a reference voltage through the sensor and reads what comes back. Cold air means high resistance and a high signal; warm air means a low one.

When the signal sits at the very top of the range, it looks like air far colder than any Reno morning, or like a sensor that is not connected at all. The computer recognizes that as a circuit fault, stores P0113 and lights the lamp. It then typically substitutes a default value so the engine keeps running.

Where emissions come in

Cold air is denser and needs more fuel. If the computer believed a false cold reading, it would add fuel the engine does not need, which raises emissions. Using a default instead is safer, but it is still a guess, so the OBD II system treats the fault as emissions-related and keeps the light on until the repair is finished.

Common causes a repair shop checks

Common causes a repair shop checks for a circuit-high code like this include an unplugged or loose connector at the sensor, a broken or chafed wire, corrosion in the connector, and a failed sensor. On many vehicles the sensor is built into the air flow sensor housing, so work on the air box or intake tube can disturb it. A repair shop decides which applies.

Recent work under the hood

If the light came on right after an air filter change or other work near the intake, mention it when you visit a repair shop. A connector that did not get pushed back fully is a well-known reason for circuit codes. Whatever the cause, avoid clearing the code yourself right before your test.

The DMV explains why: clearing codes or disconnecting the battery erases the computer's memory of its self-checks, and a vehicle tested in that state is rejected as not ready. A rejection is not a failure, but the car then needs up to a week of driving under varying conditions, city and highway, before it can be tested again.

The smog check outcome

Nevada does not measure the exhaust of a 1996 or newer light-duty vehicle; the analyzer reads the OBD II computer, and a lit check engine light is an automatic fail. So P0113 fails the test even when the car drives normally.

Testing anyway, as the DMV advises, gets you the failed report. It explains why the vehicle failed, starts the waiver process, and helps with a ten-day movement permit at reduced cost if your registration has expired.

Next steps after a fail

• Take the car to a repair shop with the failed report. The DMV recommends a 2G licensed authorized station for emissions repairs.
• Keep every receipt. A Washoe waiver needs 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.
• After the repair, give the car up to a week of mixed driving so the monitors finish, then retest.
• On a newer vehicle, ask the dealer about a recall or the federal emissions warranty first: federal law covers some expensive emission components for up to 8 years or 80,000 miles.