The P0635 code in your 2022 Hyundai Santa Fe indicates an issue with the power steering control circuit communication between the ECM and the electronic power steering (EPS) system. Your Santa Fe uses an electrically-assisted power steering system that receives information from the ECM to adjust assist levels based on vehicle speed and driving conditions.
Electronic Power Steering Integration
Unlike hydraulic power steering, your Santa Fe's EPS uses an electric motor to provide steering assist. The ECM communicates vehicle speed, engine load, and other data to the EPS control unit, which adjusts assist level accordingly. At low speeds, more assist is provided for easy maneuvering. At highway speeds, assist decreases for better road feel. P0635 indicates a problem in this communication.
Causes of Control Circuit Issues
CAN bus communication problems between the ECM and EPS module are common causes. Wiring issues, including damaged wires or corroded connectors in the communication circuit, affect data transmission. The EPS control module itself may have failed or developed communication issues. ECM configuration errors may create incompatibility with the EPS system.
Symptoms You May Notice
Steering may feel inconsistent—sometimes heavy, sometimes light. The power steering warning light illuminates on the dashboard. Speed-variable assist may not function properly. The check engine light accompanies the power steering warning. In some cases, steering remains functional but without electronic assist adjustment.
Diagnostic Steps
Using Hyundai GDS or a capable scan tool, check for communication errors between the ECM and EPS modules. Verify CAN bus integrity through network tests. Check wiring between modules for damage. Test both modules for proper operation individually. If one module was recently replaced or reprogrammed, verify configuration compatibility.