Theory Of Operation
The Variable Valve Timing (VVT) system continuously varies the Camshaft target position based on the engine operating parameters. Based on these parameters, the PCM calculates or models the optimum Camshaft position. The Camshaft angular position is varied by the oil control valve. The VVT solenoid pushes on a plunger (spring loaded spool valve) in the center of the Oil Control Valve (OCV) which directs oil pressure to the hydraulic actuator (Phaser) on the Camshaft Sprocket to change the Camshaft position relative to the Crankshaft position. The VVT Solenoid, acting on the Oil Control Valve and Phaser is controlled by the PCM. The CMP Sensor is used to monitor the position of the Camshaft.
A VVT diagnostic is performed to detect a Target Error and a Slow Response of the camshaft, problems which could potentially increase tailpipe emissions. The diagnostic is primarily performed by comparing the actual camshaft position to that of a calculated model for the camshaft position. This diagnostic is continuous once the enable conditions are met, however the Slow Response and Target Error conditions are not performed simultaneously.
- The Target Error diagnostic evaluates the actual Camshaft position versus the modeled position when the Camshaft is in a relatively stable position. The difference between the two is considered to be the amount of "error". If the error amount is greater than a calibrated threshold, it is considered failing.
- The Slow Response diagnostic is only performed when the modeled Camshaft position is moving (phasing) in a particular direction, advancing or retarding. The modeled Camshaft phasing position is created to match only the worst possible case of a passing camshaft position. If the actual camshaft phasing operates slower than the model by a calibrated threshold, it is considered failing.
If either of these diagnostics fail, the Camshaft Position Slow Response DTC will set.
There are four camshafts and two Camshaft Position (CMP) Sensors. Each CMP Sensor will detect the position of both camshafts on its correlating engine bank.
| 3.2L/3.6L VVT Component Locations | |
|---|---|
| CALLOUT | DESCRIPTION |
| 1 | VVT Actuator Bank 1 Position 1 (Intake) |
| 2 | VVT Actuator Bank 1 Position 2 (Exhaust) |
| 3 | VVT Actuator Bank 2 Position 1 (Intake) |
| 4 | VVT Actuator Bank 2 Position 2 (Exhaust) |
| 5 | Bank 1 Camshaft Sensor |
| 5A | CMP Bank 1 Sensor 1 (Exhaust) |
| 5B | CMP Bank 1 Sensor 2 (Intake) |
| 6 | Bank 2 Camshaft Sensor |
| 6A | CMP Bank 2 Sensor 1 (Exhaust) |
| 6B | CMP Bank 2 Sensor 2 (Intake) |