The P0629 code in your 2019 Genesis G80 indicates that the ECM has detected higher than expected voltage on the fuel pump control circuit. This code suggests an open circuit condition or high resistance that prevents normal current flow, causing voltage to remain elevated.
High Voltage Circuit Conditions
When the ECM attempts to energize the fuel pump relay, current should flow through the control circuit, causing a voltage drop. If the circuit is open or has very high resistance, minimal current flows and voltage readings remain high. The ECM interprets this as a circuit fault and triggers P0629.
Causes of High Voltage
An open circuit anywhere in the fuel pump control pathway is the primary cause. This includes broken wires, disconnected connectors, or corroded terminals that prevent current flow. The fuel pump relay's control coil may have failed open. A blown fuse in the control circuit also creates an open condition. The ECM's relay driver may have failed in an off or open state.
Symptoms in Your G80
Fuel pump may not prime when the key is turned on. The engine may crank but not start due to no fuel pressure. If the condition is intermittent, starting problems occur randomly. The check engine light illuminates with P0629 stored. The luxury features of your G80 continue to work, but the engine won't run without fuel.
Diagnostic Steps
Using Hyundai/Genesis GDS or a capable scan tool, check fuel pump relay command status. Measure voltage at the relay control terminal when commanded—it should drop when active. Check the entire circuit path from ECM to relay for continuity. Test the relay coil for proper resistance. If an integrated relay module is used, the entire module may require replacement.