Parts for your 2009 Mazda 6-Temperature sensors

2009 Mazda 6 temperature sensors — what they do and how to look after them

Temperature sensors absolutely are used on the 2009 Mazda 6. Technical references including the Mazda 6 (GE/GH) Workshop Manual, Mazda MS3 service information, and standard OBD‑II (SAE J1979) data lists confirm multiple temperature sensors are fitted and read by the powertrain and HVAC systems. That includes the Engine Coolant Temperature (ECT) sensor, Intake Air Temperature (IAT) sensor, ambient air temperature sensor for the climate control, automatic transmission fluid temperature (on autos), and—on the 2.2L diesel—exhaust gas temperature (EGT) sensors for DPF control.

On this model, these sensors quietly keep things sweet by letting the ECU manage fuelling, ignition timing, cooling fan operation and A/C performance. The ECT sensor is the big player: it tells the PCM how hot the engine is so it can enrich a cold start, switch fans on, and protect the engine from overheating. The IAT trims fuelling for air density, the ambient sensor helps the climate control blow the right temp, and the ATF and diesel EGT sensors protect the gearbox and aftertreatment when the going gets tough.

• Common symptoms of a dodgy temp sensor: hard cold starts, rough idle, poor fuel economy, over‑cooling/overheating, lazy A/C, erratic fan operation, or a check‑engine light with related codes (e.g. P0115–P0119 for ECT).

As for maintenance, these sensors aren’t regular replacement items, but they do benefit from a bit of love during routine servicing. Keep coolant fresh and correct—Mazda FL22 long‑life coolant typically lasts up to 10 years/200,000 km on the factory fill, then 5 years/100,000 km, always follow the vehicle’s schedule. Corroded connectors or old coolant can mislead the sensor and the ECU.

1. If replacement’s needed, confirm with live data on a scan tool. On a warm engine, ECT should typically read around 85–100 °C at operating temp.
2. Use quality OEM‑spec parts. Cheap sensors can read “close enough” but still cause grief.
3. When fitting an ECT sensor, work on a cool engine, capture coolant, and use a new sealing washer/O‑ring as specified. Torque to workshop‑manual spec and bleed the cooling system properly.
4. Inspect and clean connectors, a bit of dielectric grease can help keep moisture out.

For diesel GH models, treat EGT sensors with care—heat‑seized threads are common. Use penetrating oil, correct socket, and replace crush washers where specified to prevent exhaust leaks.

What are the signs my 2009 Mazda 6 ECT sensor is failing?

Expect hard cold starts, the temp gauge behaving oddly, cooling fans running too much or not enough, and fault codes like P0116 or P0117. Fuel economy can drop and the idle can feel off because the ECU is guessing the engine temperature.

A quick test is to check the ECT reading on a scan tool after an overnight sit: it should match ambient temperature before start, then climb smoothly to operating temp as the engine warms.

Do I need to replace temperature sensors as preventive maintenance?

Not usually. They’re replaced on condition. What’s worth doing is keeping the cooling system in top nick—fresh FL22 coolant at the right intervals, clean connectors, and fixing any wiring damage. That prevents false readings and extends sensor life.

Can I drive with a faulty temperature sensor?

Short answer: it’s risky. The car may run rich, overwork the fans, or miss an actual overheat. On diesel models, an EGT sensor fault can disrupt DPF regeneration. Best to diagnose promptly and sort it before it snowballs into bigger repairs.