Home / Nissan CEL
Code reference
Nissan Check Engine Light Codes: The Common Ones Decoded
The check-engine codes that show up most on Nissans — P0420, P0171, P0300, P0455, plus the CVT-related ones — what each means and how urgent it is.
What it isOBD2 trouble codes — the specific reason the computer lit the dash
UrgencyModerate
Safe to drive?Depends on the code — sensor/evap can wait; misfire and CVT codes can't
Typical costReading codes is free at most parts stores; fixes vary widely by code
P0420P0171P0300P0455P0744P0011
A check engine light is a doorbell; a code is who’s at the door. Until you read it, you’re guessing — and guessing is how a $200 sensor gets “fixed” with a $1,000 converter. So step one is always to pull the code, with a scanner or a free read at a parts counter.
The first letter tells you the neighborhood: P is powertrain (engine and transmission, where nearly all check-engine codes live), B is body, C chassis, U network. The number is the specific fault. The ones that turn up on Nissans again and again:
- P0420 — catalyst efficiency low. The common high-mileage code. Sometimes the converter, sometimes a lying downstream oxygen sensor. Not urgent, but the expensive one to diagnose right.
- P0171 — running lean. Too much air, not enough fuel. Think vacuum leak or a dirty mass-airflow sensor.
- P0300 / P0301–P0304 — misfire. P0300 random, the others name the cylinder. Blinking light? Don’t keep driving.
- P0455 — evap leak. Usually the gas cap. Cheap, low urgency, common.
- P0744 and the P07xx range — transmission/CVT. The Nissan-specific cluster. Paired with shuddering or limp mode, this is a transmission conversation, not a sensor.
Match the code to its urgency and the scary dashboard becomes a to-do item. Evap and slow sensor codes can ride a few days; misfire and transmission codes move to the front of the line.
The move, step by step
- Read the code first — A scanner or a free parts-store read turns the light into a P-code. Everything else depends on it.
- Check the first letter — P = powertrain (engine/trans), B = body, C = chassis, U = network. Most check-engine codes are P-codes.
- Look up the number — P0420 (converter), P0171 (lean), P0300s (misfire), P0455 (evap), P0744 (CVT) are the Nissan regulars.
- Match urgency to the code — Evap and slow sensor codes can wait. Misfire and transmission codes go to the front.
Tool for the job: a basic OBD2 scanner reads the exact code in under a minute. See scanners on Amazon →
As an Amazon Associate, Nissan Dash Decoder earns from qualifying purchases made through links on this page. It costs you nothing extra and helps keep this desk running.
Nissan owners ask
How do I read the codes behind my Nissan's check engine light?
Plug an OBD2 scanner into the diagnostic port — it's under the dash on the driver's side, near your knee. Turn the key to 'on' and the scanner lists stored codes like P0420. No scanner? Most auto-parts stores read codes free in the parking lot. Write them down before clearing anything, because the code is what tells you whether you're looking at a cheap fix or a big one.
What does P0420 mean on a Nissan?
P0420 is 'catalyst system efficiency below threshold' — the computer thinks the catalytic converter isn't cleaning the exhaust as well as it should. It's one of the most common Nissan codes at higher mileage. It doesn't automatically mean the converter is shot; a lazy downstream oxygen sensor can trigger it too, so a little diagnosis is worth it before buying an expensive converter.
Are there Nissan-specific transmission codes I should know?
Yes. Because so many Nissans use a CVT, transmission-related codes show up more than on a typical lineup. Codes in the P0700–P0900 range (for example P0744, which involves the torque converter/transmission performance) point at the transmission rather than the engine. If you see one of those alongside shuddering, slipping, or limp mode, treat it as a transmission diagnosis, not a sensor swap.
Are Nissan check engine codes the same as other cars?
The generic P0-codes (P0420, P0171, P0300, P0455 and so on) are standardized across all OBD2 vehicles, so they mean the same on a Nissan as anywhere. Nissan also has manufacturer-specific codes (often starting with P1) that a basic reader may show as a number without a description — those you look up against Nissan-specific references or have a shop interpret.
Updated 2026-07-01 · Independent reference, not a substitute for a hands-on diagnosis.