How to Fix P0685 Code: A Step-by-Step Guide

AvatarByCarl Frisch

P0685 is a diagnostic trouble code (DTC) that indicates an issue with the engine control module (ECM) power relay circuit. The ECM power relay is responsible for providing power to the ECM and other related components. When the ECM detects an issue with the power relay circuit, it will set a P0685 code.

To fix this code, you will need to identify and repair any faulty wiring or connections in the circuit. You will also need to check the ECM power relay and related components for signs of damage or failure. If necessary, you will need to replace any damaged or faulty parts so that the circuit can be restored to its proper functioning condition. Finally, you will need to reset any stored codes in order for the P0685 code not to reappear.

Identifying the P0685 Code



When your vehicle’s engine control module (ECM) detects an issue with the ECM circuit, it will store a P0685 code. This code is used to indicate a problem with the ECM relay or circuit, and can cause a wide range of issues with your vehicle’s performance. It is important to understand the meaning of this code in order to properly diagnose and fix any problems.

The ECM relay is responsible for controlling the voltage supply to the ECM, which allows it to power up and make all necessary adjustments for optimal vehicle performance. If this relay is not working correctly, then the ECM may not be able to perform its functions properly. Additionally, a faulty wiring or connection in the ECM circuit can cause a P0685 code as well.

Diagnosing the P0685 Code



When diagnosing a P0685 code, you should first check for any faulty wiring or connections in the ECM circuit. This includes ensuring that all wires are properly connected and that none are corroded or loose. You should also look for any damaged components that may be causing an issue with the circuit as well.

In some cases, it may be necessary to use a multimeter to test each wire in order to ensure that there are no issues with them. Additionally, you should check all of the relays in your vehicle’s engine compartment and replace any that are not working correctly.

Fixing the P0685 Code



Once you have identified any faulty wiring or connectors in your vehicle’s ECM circuit, then it is time to fix them. This can involve replacing damaged wires and connectors as well as replacing any damaged components such as relays or ECMs themselves. You should also ensure that all connections are secure before reassembling your vehicle’s engine compartment again.

It is important to take extra care when fixing any issues related to your vehicle’s electrical system so as not to cause further damage or create additional problems down the road. Additionally, if you are unsure of how to properly diagnose or fix any issues related to your vehicle’s electrical system then it is best to seek professional assistance from an experienced mechanic.

Causes of a P0685 Error Code



There can be several causes of a P0685 error code including poor electrical connections in the ECM circuit and defective components within this same circuit such as failing relays or modules. Poor electrical connections could include anything from loose wires and corroded connectors causing an issue with power flow through this system as well as broken wires or harnesses preventing proper communication between different components within it.

Defective components in an ECM circuit may also cause these codes including failing relays or bad modules which prevent proper communication between different parts within this system as well as incorrect voltages being sent through various parts due to failed internal circuitry within these components themselves.

Steps To Take Before Diagnosing A P0685 Error Code



Before attempting any diagnosis on an issue related to your vehicle’s electrical system such as a P0685 error code, there are certain steps you should take first such as visually inspecting all wiring and connectors for signs of damage, corrosion, wear etc., testing each wire for continuity using a multimeter if necessary and checking each component individually for proper operation by performing tests specific for that part type (e.g., resistance tests on relays). Taking these steps beforehand will help save time when diagnosing an issue related to your vehicle’s electrical system by quickly identifying any faults before attempting more complex tests which would otherwise take longer without having done these initial checks first

Checking Battery Voltage Level



One of the first steps when diagnosing a P0685 error code is to check the vehicle’s battery voltage level. This can be done easily with a digital multimeter. It is important to make sure that the battery is supplying enough power for all the components in the electrical system. If it is not, then the ECM may be unable to communicate properly with other components and cause a P0685 error.

Inspecting The ECM Fuse And Relays



The ECM fuse and relays should also be inspected when diagnosing a P0685 error code. Checking for blown fuses is important, as these can prevent power from reaching the ECM and cause an error. Testing the relays is also important as they can help supply power to other components in the system if they are working properly. If any of these parts are damaged, then they should be replaced before further diagnosis takes place.

Visually Inspecting The Electrical System



It is also important to visually inspect the electrical system when diagnosing a P0685 error code. This involves looking for loose connections and examining the wiring harness for signs of damage or wear. If any loose connections or damaged wiring are found, then they should be repaired or replaced before further diagnosis takes place.

Common Questions About A P0685 Error Code



There are several common questions about a P0685 error code that are asked by many people who have experienced this issue in their vehicle. One such question is “How common is a P0685 error?” The answer to this question varies depending on several factors such as make and model of vehicle as well as how often it has been driven, but typically these errors are not very common and usually only occur due to an underlying issue with another component in the vehicle’s electrical system. Another common question about a P0685 error code is “What are the symptoms of a P0685 error?” Generally speaking, symptoms of this type of error include loss of power or stalling while driving, difficulty starting the engine, reduced fuel economy, and illuminated check engine light on dashboard display among others.

FAQ & Answers



Q: What is the P0685 code?
A: The P0685 code is a trouble code that indicates an issue with the ECM relay circuit.

Q: What are the symptoms of a P0685 code?
A: Symptoms of a P0685 code can include engine misfires, stalling, and/or difficulty starting the engine.

Q: What are the causes of a P0685 error code?
A: Possible causes of a P0685 error code include poor electrical connections in the ECM circuit, defective components in the ECM circuit, and/or damaged wiring or components.

Q: What steps should be taken before diagnosing a P0685 error code?
A: Before diagnosing a P0685 error code, it is important to check battery voltage level, inspect the ECM fuse and relays, and visually inspect the electrical system for any signs of damage or loose connections.

Q: How common is a P0685 error?
A: The frequency of a P0685 error can vary depending on several factors such as vehicle make and model, driving conditions, and maintenance history.

In conclusion, the P0685 code can be solved by replacing a faulty PCM, replacing a blown fuse or relay, repairing a damaged wiring harness or connector, or simply resetting the ECU. To identify the exact cause of the code, it is important to perform a thorough inspection of the system and perform appropriate diagnostic tests. With proper diagnosis and repair, this code can be resolved quickly and easily.

Author Profile

Carl Frisch
Carl Frisch
With more than 30 years in the bicycle industry, I have a strong background in bicycle retailing, sales, marketing and customer service. I have a passion for cycling and a dedication to excellence. As a manager, I worked diligently to increase my capabilities and responsibilities, managing up to eleven mechanics (at Palo Alto Bicycles) and later as a working partner in my own store.

As the shop owner of Spoke n’ Word Cycles in Socorro, NM, the success of the mission was my responsibility, which I pursued passionately since we opened in 2003 through the spring of 2011. I am adept at managing owned and loan inventory, preparing weekly & annual inventory statements, and managing staff. The role as managing partner also allowed me tremendous freedom. I used this personal freedom to become more deeply involved in my own advancement as a mechanic, to spearhead local trail building, and advocating for cycling both locally and regionally.

As a mechanic, I have several years doing neutral support, experience as a team mechanic, and experience supporting local rides, races, club events. I consistently strive to ensure that bicycles function flawlessly by foreseeing issues and working with the riders, soigners, coaches and other mechanics. Even with decades of experience as a shop mechanic and team mechanic, and continue to pursue greater involvement in this sport as a US Pro Mechanic, and UCI Pro Mechanic.

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