P0128 on Nissan
Coolant Thermostat Below Regulating Temperature
P0128 on Nissan vehicles indicates coolant thermostat below regulating temperature. Au7o has documented this code across 4 Nissan models — most commonly on Altima, NV, Rogue. This code means the engine isn't reaching its proper operating temperature within the expected time, so the coolant stays below the thermostat's regulating temperature. The computer estimates how warm the coolant should be (based on run time, airflow, and intake air temperature) and compares it to the actual reading. When the engine warms too slowly or never gets hot enough, P0128 sets. The most common cause is a thermostat stuck open, which can cause reduced heater output, poorer fuel economy, and higher emissions. Typical repair costs on Nissan range from $150 to $600, depending on the specific model and root cause.
Common Causes of P0128
- •Thermostat stuck open or opening too early
- •Faulty engine coolant temperature sensor
- •Low coolant level
- •Cooling fan running constantly (overcooling)
- •Wrong-temperature-rating thermostat installed
- •Corroded or loose coolant temperature sensor connector
- •Air pockets in the cooling system
- •Faulty PCM/ECM (rare)
P0128 on Nissan by Model
Nissan Altima(1 issue)
- P0128 — Coolant Below Regulating Temperature from Thermostat Stuck Open2007-2018
On the Altima, P0128 sets when the ECM sees that engine coolant fails to reach its target operating temperature (roughly 180-200F) within the expected time/warm-up cycle. The overwhelming Altima-specific cause is a thermostat stuck open (or a thermostat that opens too early), which lets coolant circulate continuously and never lets the engine fully warm. On the 2.5L QR25DE there are effectively two temperature-control components — the main thermostat behind the cylinder head and a secondary water-control valve at the front of the engine — and best practice is to replace both together, because replacing only one frequently leaves the code active. Drivers most often notice weak cabin heat in cold weather and a temperature gauge that sits low or drops on the highway. Left unfixed it causes poor fuel economy, higher emissions, and can fail an emissions/smog test.
Nissan NV(1 issue)
- Radiator Plastic End Tank Cracking and Coolant Leak2012-2021
The Nissan NV cargo van uses a radiator with plastic end tanks that develop cracks from heat cycling and vibration inherent to commercial van use. The cracks typically form at the crimp joint between the plastic tank and aluminum core. The V8 NV 2500/3500 models are more susceptible due to higher operating temperatures, especially when loaded to capacity. A cracked radiator causes gradual coolant loss that can lead to overheating if not caught early.
Nissan Rogue(1 issue)
- P0128 — Coolant Below Regulating Temp from Stuck Thermostat / Water Control Valve (QR25DE)2008-2020
P0128 means the engine did not reach normal operating temperature (about 195-205°F) within the ECM's expected time, or coolant temperature drops at highway speed. The QR25DE 2.5L in the Rogue has a distinctive cooling system with TWO regulating components: the main thermostat AND a secondary 'water control valve.' Either one stuck open lets coolant flow too freely, so the engine runs cool and the ECM sets P0128. This is the single most common trigger on this platform, and a frequent gotcha is that replacing only the main thermostat leaves the still-stuck water control valve, so the code returns. A stuck-cool engine hurts fuel economy, delays proper cabin heat, and keeps the engine in open-loop enrichment longer.
Nissan Sentra(1 issue)
- P0128 — Coolant Below Regulating Temperature from Thermostat Stuck Open2013-2019
On the Sentra, P0128 is set when the ECM sees the engine failing to reach normal operating temperature within an expected time — almost always a thermostat that has failed stuck open, so coolant circulates continuously and the engine runs cool. The 1.8L MRA8DE cars (2013-2019) use a more complex two-piece setup (a thermostat plus a water/coolant control valve), so it is worth identifying which unit is stuck; a false-low reading from a bad engine coolant temperature sensor can mimic the same code.
Looking for P0128 on a different make?
View P0128 across all makes →Frequently Asked Questions
What does P0128 mean on Nissan?▼
P0128 stands for "Coolant Thermostat Below Regulating Temperature." This code means the engine isn't reaching its proper operating temperature within the expected time, so the coolant stays below the thermostat's regulating temperature. The computer estimates how warm the coolant should be (based on run time, airflow, and intake air temperature) and compares it to the actual reading. When the engine warms too slowly or never gets hot enough, P0128 sets. The most common cause is a thermostat stuck open, which can cause reduced heater output, poorer fuel economy, and higher emissions. On Nissan specifically, this code is documented across 4 models.
What causes P0128 on Nissan vehicles?▼
Common causes on Nissan: Thermostat stuck open or opening too early, Faulty engine coolant temperature sensor, Low coolant level, Cooling fan running constantly (overcooling), Wrong-temperature-rating thermostat installed. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0128 on a Nissan?▼
Repair costs on Nissan range from $150 to $600, depending on the specific model and root cause.
Which Nissan models have P0128 documented?▼
Au7o has documented P0128 on 4 Nissan models: Altima, NV, Rogue, Sentra.