Newer Subaru vehicles are known to encounter issues with their Variable Valve Timing (VVT) systems, often storing fault data in the EEPROM. Traditionally, clearing this data has been a challenge, often requiring costly ECM replacement or complex EEPROM work. Subaru Technical Service Bulletin 02-163-16r even specifies ECM replacement as the necessary solution. However, a more efficient and cost-effective method has emerged, eliminating the need for ECM replacement or intricate EEPROM procedures. This method leverages readily available OBD scan tools to reset the cam phaser ranges, simplifying the repair process.
This innovative solution utilizes the inspection mode present in Subaru vehicles, combined with the capabilities of standard OBD scan tools such as Launch or Autel (compatibility may extend to other brands). The process begins by activating inspection mode, typically by installing a designated fuse in the underhood fuse panel. The exact fuse location can vary depending on the Subaru model year, but this information is readily available in service documentation. Once the inspection fuse is in place and the ignition is turned on, the cooling fans may cycle – this is a normal indication of inspection mode activation.
Next, using your OBD scan tool, connect to the vehicle’s ECM and navigate to the special functions menu. Within this menu, locate and select the option to change the test mode. Activating this test mode will typically cause the check engine light to begin flashing. While the test mode is active, return to the scan tool’s main menu and perform a code clearing procedure. After clearing the codes, turn the ignition off, remove the inspection fuse from the underhood fuse panel, and then turn the ignition back on. Verify that the VVT system values have been successfully reset.
OBD Scan Tool Interface Displaying Special Functions Menu
This procedure has been successfully tested and verified on a range of Subaru models, including 2015, 2016, and 2019 vehicles, demonstrating its effectiveness in resetting cam phaser ranges for both in-range and out-of-range values. This method offers a significant advantage by providing a quicker and more economical alternative to ECM replacement for resolving VVT system data issues.
This breakthrough was inspired by the work of Robbie Magill, who shared a similar technique for resetting the misfire profile learning on timing belt engines. While initial attempts to apply this to VVT systems were unsuccessful, collaboration and further investigation by Rob Dotterer and Joe Bonino led to the crucial discovery of activating the test mode via the scan tool after engaging inspection mode. This final piece of the puzzle unlocked the solution for resetting Subaru VVT systems efficiently.
For a visual guide and detailed walkthrough of this process, refer to the video demonstration available here: youtu.be/aR6fHMxlZgU. This method empowers technicians and DIY enthusiasts to address Subaru VVT system data issues effectively using standard OBD scan tools, saving both time and resources compared to traditional ECM replacement.
