Loading...

Infiniti Q40 Engine Coolant Temperature Sensors

Infiniti Q40 Engine coolant temperature sensors

Starting at $7.95, AutoBuffy stocks 7 engine coolant temperature sensors from Delphi, Four Seasons, and Standard Ignition for the Infiniti Q40. The ECT sensor measures coolant temperature and sends that data to the ECU, which uses it to control fuel trim, ignition timing, and cooling fan operation. A failed sensor triggers poor fuel economy, rough cold starts, and a check engine light.

Signs your Infiniti Q40 needs a new engine coolant temperature sensor

  • Check engine light on with a stored code P0115–P0119 (ECT circuit fault)
  • Engine runs rich and fuel economy drops noticeably, especially during warm-up
  • Hard or rough cold starts because the ECU cannot calculate proper cold-start fueling
  • Cooling fan runs continuously or never kicks on, even when the engine is hot
  • Temperature gauge reads erratically, pegs full hot immediately, or stays at cold
  • Black smoke from the exhaust or a noticeable fuel smell from over-fueling

Which engine coolant temperature sensor should you buy for your Infiniti Q40?

The main decision is matching the correct sensor to your engine's specific port location and connector type — many Q40 engines use more than one coolant temperature sensor, one for the ECU and one for the dash gauge, and they are not interchangeable. Beyond fitment, choose between OE-equivalent and performance-grade sensors based on whether your vehicle is stock or modified.

OE-Equivalent (ECU/PCM sensor)
Best for
Daily drivers, stock engines
What you get
Direct plug-and-play fit, calibration matched to factory ECU fuel and timing maps
OE-Equivalent (gauge/cluster sensor)
Best for
Fixing inaccurate dash temperature readings
What you get
Separate resistive sensor tuned to the instrument cluster, not the engine management system
High-Quality Aftermarket (brass or stainless tip)
Best for
High-mileage or high-heat applications
What you get
More corrosion-resistant tip material, longer service life in older cooling systems with scale buildup
OEM / Dealer-Grade
Best for
Owners wanting exact factory spec
What you get
Identical to the original part, highest calibration accuracy, typically highest price point

Engine coolant temperature sensors brands we stock for your Infiniti Q40

Delphi
1 option · from $51.95
Four Seasons
1 option · from $20.95
Standard Ignition
1 option · from $23.95
Autotecnica
1 option · from $7.95
VEMO
1 option · from $16.95
GPD
1 option · from $10.95
Beck/Arnley
1 option · from $19.95

Replacing the engine coolant temperature sensor on a Infiniti Q40

Easy⏱ 30–60 minutesScan tool or OBD-II code reader (to confirm code and clear after repair)Deep socket or sensor socket sized to fit the ECT sensor hexRatchet and short extensionDrain panThread seal tape or manufacturer-supplied sealing washer

Allow the engine to cool completely before starting — hot coolant under pressure is dangerous. Partially drain the cooling system below the sensor location, unplug the electrical connector, and unthread the old sensor. Install the new sensor hand-tight first, then snug it firmly with the socket without overtightening, as the sensor body can crack. Refill and bleed the cooling system, then clear any stored fault codes with a scan tool and confirm the temperature gauge and cooling fan behavior return to normal.

Frequently asked questions

How much does it cost to replace engine coolant temperature sensors on a Infiniti Q40?
The sensor itself starts at $7.95 for the Infiniti Q40. DIY total cost is usually just the part plus a small amount of fresh coolant to top off after removal. A shop will add one to two hours of labor, so expect a higher total for professional installation depending on sensor location and accessibility.
Can I drive my Infiniti Q40 with a bad coolant temperature sensor?
You can drive short distances, but it is not recommended. A failed ECT sensor causes the ECU to run a default or open-loop fuel strategy, which often means over-fueling. This wastes fuel, washes oil off cylinder walls, raises emissions, and can foul spark plugs. Fix it promptly to avoid secondary damage.
Will a bad coolant temperature sensor cause my Infiniti Q40 to overheat?
It can. If the sensor sends a false cold signal, the ECU may not command the electric cooling fan to turn on at the correct threshold. Without proper fan activation, especially at low road speeds or in stop-and-go traffic, coolant temperatures can climb high enough to cause genuine overheating and engine damage.
How many coolant temperature sensors does a Infiniti Q40 have?
Most Infiniti Q40 engines have two coolant temperature sensors — one wired to the ECU or PCM that controls fuel delivery and ignition timing, and a second wired to the instrument cluster that drives the dashboard temperature gauge. They serve different functions and must be replaced with the correct corresponding part for proper operation.
How long does an engine coolant temperature sensor last on a Infiniti Q40?
ECT sensors typically last many years and well into high mileage, but they degrade over time due to heat cycling, coolant contamination, and corrosion on the tip or connector. Neglected coolant that is acidic or full of scale accelerates failure significantly. Replacing coolant on schedule helps extend sensor life.
Do I need to drain the coolant to replace the ECT sensor on my Infiniti Q40?
Not always, but expect some coolant loss. The sensor threads directly into the coolant passage, so removing it while the system is full will cause spillage. Many technicians partially drain the cooling system below the sensor's location first. Have fresh coolant ready to top off the system after the new sensor is installed and torqued.

Shop engine coolant temperature sensors by year for the Infiniti Q40

2015

More parts for your Infiniti Q40

Brake Pad SetIgnition Coil SetWiper BladeEngine Timing Belt TensionerVehicle BatteryCatalytic ConverterCanister Vent Solenoid ConnectorEngine Coolant Thermostat Housing Assembly

Engine coolant temperature sensors for other Infiniti models

Infiniti FX50Infiniti G35Infiniti I30Infiniti QX55Infiniti G37Infiniti JX35