Parts for your 2015 Mazda Cx-9-Camshaft sensor

2015 Mazda CX-9 camshaft sensor: purpose, servicing and FAQs

Technical sources confirm the 2015 Mazda CX-9 (3.7-litre MZI/Cyclone V6) is fitted with camshaft position sensors. In the Mazda Workshop Manual for this model year, the Engine Control System section details “Camshaft Position (CMP) Sensor — Inspection/Removal/Installation,” plus fault diagnosis for CMP-related DTCs such as P0340/P0341/P0344. The 2015 CX-9 wiring diagram likewise shows two CMP sensors (Bank 1 and Bank 2) providing inputs to the PCM for variable valve timing and sequential injection. These factory references make it clear the camshaft sensor is essential on this vehicle.

The camshaft sensor on a 2015 Mazda CX-9 keeps the V6 in sync by telling the powertrain control module exactly where each cam is in its rotation. Teaming up with the crank sensor, it lets the PCM fire the injectors and coils at the right moment and command the variable valve timing phasers. That means easier cold starts, smoother idle, better fuel economy and emissions, and solid pull when it’s time to overtake.

It’s not a scheduled service item, but it does benefit from good habits. Clean engine oil is key because the VVT system relies on oil pressure, sludgy oil can cause cam timing performance issues that look a lot like a failing sensor. During routine servicing, a quick check of the CMP connectors and loom routing under the bonnet is smart—heat, oil weep, or a rubbed-through harness can cause intermittent faults.

When the sensor or its circuit plays up, the CX-9 may show a Check Engine light and store codes like P0340/P0341/P0344, along with hard starting, rough idle, misfires, poor fuel economy, or a sudden lack of go. Before swapping parts, it’s worth scanning live data, checking for loose pins, corrosion, oil intrusion at the connector, and verifying 5 V reference, ground, and signal. The CMPs on this engine are three-wire Hall-effect sensors, one on each bank.

• Replacement tips: disconnect the battery, remove the engine cover, unplug the sensor, undo the hold-down bolt, and ease the sensor out. Lightly oil the new O-ring, seat the sensor fully, refit the bolt to factory torque, and route the loom as original.
• Parts choice: stick with quality OEM-equivalent sensors—cheapies can cause timing sync gremlins.
• Afterwards: clear codes, start the engine, and let it idle to stabilise. A short relearn drive helps the PCM optimise cam timing.

Access on the front bank is straightforward from the radiator side, the rear bank is tighter against the firewall, so patience (and a small ratchet) helps. If the vehicle has clocked high kilometres and one sensor has failed intermittently, replacing the pair can be sensible, but it’s not mandatory—diagnosis should lead the decision.

FAQs

How many camshaft sensors does a 2015 Mazda CX-9 have?
It has two camshaft position sensors—one for Bank 1 and one for Bank 2. The PCM uses both to manage sequential injection and variable valve timing, so a fault on either bank can affect starting, idle quality, and power delivery.

Where are the camshaft sensors located?
They sit at the ends of the cylinder heads near the cam gears—one toward the radiator side (front bank) and one toward the firewall (rear bank). Remove the plastic engine cover for a clear view, each sensor has a three-pin connector and a single hold-down bolt.

Do both sensors need replacing at the same time?
Not necessarily. Replace the sensor on the bank that’s flagged by diagnostics. If the vehicle has high kilometres and shows intermittent issues on both banks, replacing them as a pair can prevent repeat visits, but always verify with scan data and wiring checks first.