What does it mean?
The internal combustion engine needs three basic things to start and run: air, fuel, and spark. With regards to this DTC (diagnostic trouble code), we’ll be focusing on fuel. The fuel system includes the fuel tank, a low-pressure fuel pump, sometimes a high-pressure fuel pump, fuel tubes and hoses, a fuel pressure regulator, and the fuel injectors. The fuel pump and fuel injectors are operated electrically and electronically, so there are also fuses, relays, and a controller for these.
Usually, the controller is part of the ECM (engine control module), though some vehicles, such as some diesels, may have a separate fuel injector driver module. Usually, the fuel pump relay is commanded by the ECM. The ECM grounds the fuel pump relay control or primary circuit, which then feeds power to the fuel pump using the power or secondary circuit. On some vehicles, turning the key on will turn the pump, on for a few seconds, to prime the system.
If the ECM detects crank but not engine starting, using the RPM signal from the crank position sensor, it will turn off the fuel pump after a set period. To ensure proper fuel system function, everything needs to work in concert. If there is insufficient fuel pressure, the fuel injectors won’t be able to deliver fuel properly, for example. Insufficient fuel pressure can be caused by any number of electrical problems. The ECM monitors the fuel pump relay circuit for voltage.
If voltage malfunctions, it will set DTC P0230, which is defined as “Fuel Pump Relay – Circuit Malfunction.” “Circuit Malfunction” indicates that there is a malfunction in the control circuit, as opposed to a fault in a sensor or other component. With “Circuit Malfunction” codes, replacement of sensors and components in the affected circuit will almost never resolve the problem, since as the code suggests, the trouble is in the circuit .
This distinction between “circuit” and “sensor/component” is a great help to anyone trying to diagnose a circuit malfunction code, since it narrows the list of possible causes down considerably.
The causes of “Circuit Malfunction” codes are much the same as those for “Open Circuits” i.e., broken wiring, poor connections across electrical connectors or previously repaired wiring, loss of ground that prevents current flow, blown fuses, defective relays, faulty switches, or any of a host of other issues and problems that prevents a flow of current through wiring. Issues like high/low/intermittent voltages can set a “Circuit Malfunction” code on some applications.
Moreover, “Circuit Malfunction” codes could also indicate a problem with negative current control / flow, as well as issues with failed or failing PCM’s (Powertrain Control Modules), although control module failure is a rare event.