A P0636 code in your 2021 Kia Sorento indicates low voltage in the power steering control circuit. This code is more specific than P0635, telling us the communication signal between the ECM and electronic power steering system is reading below normal voltage levels.
Understanding Low Circuit Voltage
The communication circuit between the ECM and EPS module operates at specific voltage levels. When voltage drops below the expected range, it indicates either excessive resistance (causing voltage drop), a short to ground pulling voltage down, or inadequate power supply to the circuit. P0636 triggers when the ECM detects these low readings.
What Causes Low Voltage
Corroded connectors or terminals create resistance that drops voltage. A short to ground in the communication wiring pulls voltage lower than it should be. Weak vehicle battery or charging issues affect available voltage for all systems. The ECM's power steering communication driver may have partially failed. The EPS module itself may be loading down the circuit due to internal issues.
Symptoms in Your Sorento
Power steering assist may be reduced or absent at certain speeds. Warning lights for both check engine and power steering illuminate. Steering may feel heavier than normal, especially at low speeds. The EPS system may enter a fault mode that limits functionality.
Diagnostic Procedure
Test battery and charging system voltage first—this affects all circuits. Using Kia KDS, monitor the power steering control circuit voltage. Compare readings to specifications. Inspect wiring for physical damage, corrosion, or potential ground shorts. Disconnect and test each component individually to isolate the source of low voltage.