It has come to light that newer Subaru vehicles are encountering challenges with their Variable Valve Timing (VVT) systems. Specifically, data is being stored within the EEPROM (Electrically Erasable Programmable Read-Only Memory), and conventionally, clearing this data necessitates either replacing the Engine Control Module (ECM) or undertaking intricate EEPROM workarounds. This issue is even acknowledged in Subaru Technical Service Bulletin (TSB) 02-163-16r, which officially recommends ECM replacement as the resolution.
However, there’s now a more streamlined solution available that bypasses the need for ECM replacement or complex EEPROM manipulation. This method allows for an ECM reset using readily available scan tools, potentially even tools applicable to models around the 2010 Impreza Ecm Reset Scan Tool era, although this specific procedure is verified for newer models.
Here’s a step-by-step guide to perform this ECM reset:
- Initiate Inspection Mode: Begin with the vehicle ignition turned off. Locate the inspection mode fuse location within the underhood fuse panel. This location can vary depending on the Subaru model year, so consult your vehicle’s service information for precise identification. Install a fuse in the designated inspection mode slot.
- Power Up and Observe: Turn the ignition key to the “on” position (without starting the engine). You may hear the engine cooling fans begin to cycle as the system enters inspection mode.
- Scan Tool Connection: Employ a professional-grade scan tool, such as Launch or Autel (compatibility may extend to other scan tool brands as well). Establish a connection to the vehicle’s ECM using the scan tool interface.
- Access Special Functions: Navigate within the scan tool menu to locate “Special Functions” or a similarly named section that allows for advanced ECM controls.
- Engage Test Mode: Within the Special Functions menu, look for an option related to “Test Mode” or “Change Test Mode.” Select this option to activate the ECM’s test mode. Upon activation, the check engine light on the dashboard should begin to flash, indicating test mode is active.
- Clear Diagnostic Trouble Codes (DTCs): While test mode remains active (check engine light flashing), return to the main diagnostic menu of the scan tool and initiate the “Clear Codes” or “Erase DTCs” function. This step is crucial for resetting the VVT system data.
- завершение Reset Procedure: Turn the ignition key back to the “off” position. Physically remove the inspection fuse that was installed in the underhood fuse panel in step 1.
- Verification: Turn the ignition key back to the “on” position. Using the scan tool, verify that the ECM values related to the VVT system have been successfully reset to their default or expected ranges.
This procedure has been successfully validated on Subaru vehicles from model years 2015, 2016, and 2019. The reset has proven effective both in vehicles exhibiting normal VVT values and those with values outside of the acceptable range, demonstrating its robustness in addressing the VVT data storage issue.
This innovative approach is inspired by the work of Robbie Magill, who initially shared a similar methodology for resetting the learning misfire profile on timing belt engines. While initial attempts to adapt that method were unsuccessful, collaborative efforts and insights from Rob Dotterer and Joe Bonino were instrumental in pinpointing the critical missing element: activating the test mode within the scan tool after engaging inspection mode via the fuse. Thanks to these combined efforts, a practical solution for resetting these Subaru ECMs is now available.
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