Toyota Celica 2005 Repair Manual page 543

DI−344
CIRCUIT INSPECTION
DTC P0010
CIRCUIT DESCRIPTION
The Variable Valve Timing (VVT) system includes the ECM, the Oil Control Valve (OCV) and the VVT control-
ler. The ECM sends a target "duty−cycle" control signal to the OCV. This control signal, sent to the OCV,
regulates the oil pressure applied to the VVT controller. Camshaft timing control is performed based on en-
gine operation conditions such as the intake air volume, throttle position and engine coolant temperature.
The ECM controls the OCV, based on the signals output from the sensors. The VVT controller regulates the
intake camshaft angle using oil pressure through the OCV. As a result, the relative position between the cam-
shaft and the crankshaft is optimized, and the engine torque and fuel economy improve, and exhaust emis-
sions decrease under overall driving conditions. Also, the ECM detects the actual valve timing using signals
from the camshaft position sensor and crankshaft position sensor, and performs the feedback control. This
is how target valve timing is verified by the ECM.
Crankshaft Position Sensor
Mass Air Flow Sensor
Throttle Position Sensor
Engine Coolant Temp. Sensor
Vehicle Speed Signal
Camshaft Position Sensor
DTC No.
Open or short in Oil Control Valve (OCV) circuit
P0010
(1 trip detection logic)
MONITOR DESCRIPTION
After the ECM sends the "target" duty−cycle signal to the OCV (Oil Control Valve), the ECM monitors the
OCV current to establish an "actual" duty−cycle. When the actual duty−cycle ratio varies from the target
duty−ratio, the ECM sets a DTC.
2005 CELICA (RM1131U)
DIAGNOSTICS
Camshaft Position "A" Actuator circuit
(Bank 1)
DTC Detecting Condition
− ENGINE (2ZZ−GE)
ECM
Target Valve Timing
Feedback
Correction
Actual Valve Timing
S Open or short in oil control valve circuit
S Oil control valve for VVT−i
S ECM
542
Camshaft Timing
Oil Control
Valve (OCV)
Duty Control
Trouble Area
DIC75−02
A21252