Parts for your 2004 Toyota Prius-Camshaft sensor

2004 Toyota Prius Camshaft Sensor

Yes, the 2004 Toyota Prius (NHW20, 1NZ‑FXE) does use a camshaft position sensor, and it’s very relevant to how the hybrid starts and runs. This is clearly shown in Toyota’s service literature: the Repair Manual details DTCs for the camshaft position sensor circuit (e.g., P0340/P0341 – G signal), the Electrical Wiring Diagram shows the camshaft position sensor (often labelled “G2”) wired to the ECM, and the New Car Features manual explains how VVT‑i and synchronisation rely on that G signal. Toyota’s Electronic Parts Catalogue also lists a “Sensor, Camshaft Position” for the 2004 Prius.

What does it do? The camshaft sensor tells the engine computer exactly which stroke each cylinder is on so it can line up fuel injection and spark with the crankshaft signal. In the Prius, that accuracy is extra important because the engine can be stopped and started by the hybrid system at any time. The sensor also lets the ECM monitor and control intake VVT‑i, helping with smoother starts, better torque at low revs, clean emissions, and tidy fuel economy around town.

When this sensor plays up, the check engine light usually pops on with codes like P0340 or P0341. Drivers may notice hard starting (or no start when trying to make the car READY), a rough idle when the engine does run, a flat spot in performance, or a bump in fuel use. Sometimes it’s not the sensor itself but a damaged connector, oil contamination at the sensor O‑ring, or a wiring issue between the sensor and the ECM.

Servicing-wise, it’s not a regular replacement item. During routine servicing, it’s smart to check the harness for chafing, make sure the connector is snug and clean, and keep on top of oil quality—dirty oil can upset VVT‑i operation and masquerade as a sensor fault. If replacement is needed, keep hybrid safety in mind: power the car fully OFF, remove the smart key from the cabin, and disconnect the 12‑volt negative terminal so the engine can’t crank itself. The sensor sits on the timing‑chain end of the cylinder head, it’s held by a single bolt and sealed with an O‑ring. Swap the O‑ring, lightly oil it, seat the sensor cleanly, tighten the bolt to factory spec, reconnect the 12‑volt, clear codes, and road‑test. If faults persist, look at the VVT‑i oil control valve, timing chain stretch, or wiring integrity before throwing more parts at it.

• Common signs: MIL on, P0340/P0341, hard or no start, rough idle, higher fuel use.
• Good practice: inspect connector and loom, replace O‑ring with the sensor, use quality parts.

Popular questions about the 2004‑Toyota‑Prius camshaft sensor

Where is the camshaft sensor on a 2004 Prius?
It’s mounted on the intake side of the cylinder head at the timing‑chain end. Look under the bonnet on the driver’s side (RHD markets) near the upper timing cover, you’ll see a small sensor with a single retaining bolt and a two‑pin connector.

What codes point to a bad camshaft sensor on a 2004 Prius?
The big ones are P0340 (Camshaft Position Sensor Circuit) and P0341 (Camshaft Position Sensor Range/Performance). These can also be triggered by wiring faults, a loose connector, oil intrusion at the O‑ring, or VVT‑i issues, so it pays to test before replacing.

Can a 2004 Prius run without a camshaft sensor?
Not reliably. The ECM needs the cam signal to sync fuel and spark with the crank signal, especially during hybrid start‑ups. Without a clean cam signal, the car may refuse to go READY, crank repeatedly, or run roughly with the MIL illuminated.