Circuit Description

The Camshaft Position (CMP) sensor consists of a magnet and an iron core which is wrapped with copper wire, and is installed onto the cylinder head. When the camshaft rotates, each of 3 teeth on the camshaft passes through the CMP sensor. This activates the internal magnet in the sensor, generating a voltage in the copper wire. The camshaft rotation is synchronized with the crankshaft rotation. When the crankshaft turns twice the voltage is generated 3 times in the CMP sensor. The generated voltage in the sensor acts as a signal, allowing the ECM to locate the camshaft position. This signal is then used to control ignition timing, fuel injection timing, and the VVT system.

Fig 1: DTC Trouble Detection Chart (DTC P0340/0341)

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

HINT:

• DTC P0340 indicates a malfunction relating to the CMP sensor (+) circuit (the wire harness between the ECM and CMP sensor, and the CMP sensor itself).
• DTC P0341 indicates a malfunction relating to the CMP sensor (-) circuit (the wire harness between the ECM and CMP sensor, and the CMP sensor itself).

Reference: Inspection using an oscilloscope.

HINT:

• The correct waveform is as shown on the left.
• G2+ stands for the CMP sensor signal, and NE+ stands for the Crankshaft Position (CKP) sensor signal.

Fig 2: View Of ECM And CMP Sensor Signal Waveform

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.