What is the fault code P0685? What is the ECM/PCM Power Relay Control Circuit open fault? How can you fix the fault code P0685? What are the causes and symptoms of the P0685 error code?
What is the P0685 Fault code? What does it signify?
The engine control module or powertrain controller module (PCM), which performs various actions within the engine and transmission, aims to maximize efficiency. Through a power relay, the battery supplies the electrical current required for the computer to work. The power relay’s job is to control the voltage flow to the PCM, and supply enough power to run the system. A P0685 fault code is triggered when the PCM detects the circuit is not closed as it should.
Relay operation is quite simple. The relay’s working structure is simple. It is usually set to the ON position, and the battery voltage flows continuously to it. The relay’s small coil is activated when the ignition switch is in the ON position. After that, the electromagnet causes two contacts to close. This completes the circuit, and the electrical current is sent from the battery to a PCM via a fused circuit.
The PCM continuously checks the voltage level in the power relay circuit. The PCM will set the fault code P0685 if it detects low voltage, or no voltage in the circuit.
Note: This code will only be applied to vehicles that use a relay power source for the PCM. Some applications use an alternative power relay, such as a fused circuit.
P0685 fault codes can be found on many vehicles, including, but not limited, to Honda, Audi and Isuzu models.
What Are the Possible Causes of P0685 Fault Codes?
Below are some reasons to set fault code P0685:
- – ECM/PCM power relay defect
- – Corroded, shorted or disconnected wires and/or cables, including battery terminals.
- – Blown PCM fuse
- – Defective ignition switches
- – Low battery voltage
- – Defective ECM/PCM (rarely)
What are the symptoms for P0685 Malfunction Codes?
These symptoms may be present in vehicles with code P0685.
- – Illumination at the check engine lights
- – There are no lights on the instrument panel
- – If there is no starting condition, the engine might not start at all
- – Engine may not start but it starts
- – In cold weather, hard starting the engine
- – Engine stalling right after starting
- – The ECM/PCM has the ability to enter fail-safe mode in order to limit engine power
How do I fix the P0685 fault code?
This code refers to electrical components. Do not rush to make a decision. This can be a costly repair and often the only option to resolve the problem. This fault code is typically caused by corroded or loose connections to the relay. They should be checked first.
Some repairs that could resolve the P0685 fault code are:
- – Repair of shortcircuits or damaged terminals or connections
- – Relay for powertrain control module replacement
- – Battery cables and/or connectors can be replaced
- – Replacing blown fuse
- – Replacing fuse box
How serious is the P0685 Fault code?
Your vehicle may still stop if it starts with a P0685 fault code. This code can affect all security components. You may lose your headlights, the lights on the instrument panels, and the traction controller or ABS system could be disabled. This code must be resolved immediately to avoid any damage or accidents.
