How do you repair code p 1604?

Code P1604 typically indicates a problem with the engine control module (ECM) or issues related to the vehicle's power supply. To repair it, first, check the battery and charging system to ensure proper voltage and connections. Inspect the wiring and connectors to the ECM for any signs of damage or corrosion. If these components are functioning correctly, consider reprogramming or replacing the ECM if necessary.