This bulletin applies to 2017 Subaru Impreza and 2015-2017 WRX and WRX STI vehicles. A new VDC (Vehicle Dynamics Control) module and HCU (Hydraulic Control Unit) have been designed to address customer concerns regarding a clicking or ticking type noise coming from the driver’s side footrest area. The new modules incorporate logic with enhanced internal solenoid and motor control characteristics.
The new control unit was incorporated into production on WRX and WRX STI, starting with VIN H9840542.
The new hydraulic unit assembly is available as follows:
P/N APPLICATION
27596VA073......................2017 WRX/WRX STI
27596FL00B......................2017 Impreza (w/o EyeSight)
27596FL01B......................2017 Impreza (w/EyeSight)
After confirming the customer’s concern, open the hood and verify that the sound is actually coming from the VDCCM & HCU and not another component.
Connect the SM4 and access data monitoring for the brake control system. Select the data for Motor Relay Signal and Motor Relay Monitor Voltage (V) as shown in the accompanying illustration.
Inspect the value for Motor Relay Voltage. If any spikes of voltage exceeding 0.2V are identified while the Motor Relay Signal shows either ON or OFF, the VDCCM&HCU must be replaced.
About the Author
Mike Mavrigian
Motor Age Editor
Mike Mavrigian has written thousands of automotive technical magazine articles involving a variety of specialties, from engine building to wheel alignment, and has authored more than a dozen books that crisscross the automotive spectrum. Mike operates Birchwood Automotive, an Ohio shop that builds custom engines and performs vintage vehicle restorations. The shop also features a professional photo studio to document projects and to create images for articles and books.