| CAUTION | If ECM replacement is instructed in following testing, always ensure ECM harness connector and ground circuits are okay. If either are defective, repair and repeat testing to confirm ECM malfunction. If ECM is replaced, ECM must be programmed with proper ignition key code for engine immobilizer system. For programming procedures, see COMPUTER RELEARN PROCEDURES - IMPORT article in GENERAL INFORMATION, or appropriate ENGINE IMMOBILIZER SYSTEMS article in ACCESSORIES & EQUIPMENT. |
Note. For component location, see appropriate illustration in THEORY & OPERATION article.
Circuit Description
The Variable Valve Timing (VVT) system controls intake valve timing in response to driving conditions. Engine Control Module (ECM) controls Variable Valve Timing (VVT) Oil Control Valve (OCV) to ensure correct valve timing. VVT OCV is located is mounted on intake side of cylinder head, on flywheel side of engine. Oil pressure controlled by the VVT OCV is supplied to the VVT controller. VVT controller then changes relative position between camshaft and crankshaft. VVT controller is located on the back of intake camshaft. DTC P1656 is for bank No. 1. DTC P1663 is for bank No. 2. DTC is set if ECM detects an open or short in VVT OCV circuit. Possible causes are
- VVT OCV circuit is open or shorted.
- Defective VVT OCV.
- Defective ECM.
Diagnostic Aids
Using Toyota hand-held tester or scan tool, read FREEZE FRAME data. Freeze frame data records engine conditions when malfunction is detected.