P0685 code — how to fix error fast

If there’s something wrong with the performance of your car and the scanner tool shows the code P0685, the situation can be rather serious. It takes both understanding the P0685 code meaning and taking immediate action to repair the problem behind it to save your vehicle from severe engine damage.

We know it sounds pretty dire, but our team will give you a helping hand in diagnosing and fixing the issue. We’ll also give you a hint on some main reasons behind the code to help you figure out what caused it in your car, and go over some car models that are most commonly associated with this code.

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What does the P0685 code mean?

The P0685 code indicates a problem with the ECM/PCM power relay control circuit. The ECM/PCM (Engine Control Module/Powertrain Control Module) is responsible for controlling various functions of the vehicle, including the engine and transmission. The power relay control circuit is a vital part of this system, as it provides power to the ECM/PCM. When the power relay control circuit malfunctions, it can cause a range of issues with the vehicle’s performance and drivability.

To put it into perspective, it could mean bad things for your car’s engine performance, idle speed, and a drastic change in your car’s fuel consumption. So, there’s no point in wasting any time while figuring this issue out and it takes addressing it promptly to make sure your car’s computer keeps working properly.

What causes the P0685 code?

There are several potential causes of the P0685 code, including a faulty ECM/PCM power relay, damaged wiring or connectors in the power relay circuit, or a malfunctioning ECM/PCM. It is essential to diagnose the specific cause of the code to address it effectively, so here’s a complete guide on potential causes of it:

Problems with the ECM power relay

The ECM/PCM power relay is responsible for providing power to the vehicle’s ECM or PCM. If this relay fails, the ECM or PCM will not receive power, which can cause a variety of issues, including setting the P0685 code.

Wiring issues

The wiring that connects the ECM/PCM power relay to the ECM or PCM can become damaged or corroded over time. This can cause an open circuit or a short circuit, which can trigger the P0685 code.

Problems with the ECM

In some cases, the P0685 code can be caused by a failed ECM or PCM. This is rare, but it can happen if there is an internal fault in one of these modules.

Failed battery or alternator

A failed battery or alternator can also cause the P0685 code to appear on some vehicles. This is because these components are responsible for supplying power to the vehicle’s electrical system, including the ECM or PCM.

Which car models does the P0685 code affect the most?

The P0685 code can appear in various car models, but it is most common in Honda and Acura vehicles. This is because these vehicles have a specific design that makes them more susceptible to power relay issues. We’ve done some more digging to give you completely verified information, and these are the models that came up as most prone to the code P0685:

• Honda Civic: The Honda Civic is one of the most popular cars on the road today, and it’s also one of the models that are most likely to experience the P0685 code. This is because many Civic models use a specific type of ECM/PCM power relay that is known to fail over time.
• Ford F-150: The Ford F-150 is another vehicle that is frequently affected by the P0685 code. This is because many F-150s use a similar type of ECM/PCM power relay as the Civic, which can also fail over time.
• Jeep Grand Cherokee: The Jeep Grand Cherokee is a mid-size SUV that has been in production since 1993. While it’s a popular and reliable vehicle, some Grand Cherokees have been known to experience issues with the ECM/PCM power relay circuit, leading to the P0685 code.
• Dodge RAM: The Dodge Ram 1500 is a full-size pickup truck that has been in production since 1981. Some Ram models have been known to experience issues with the ECM/PCM power relay circuit, which can trigger the P0685 code.

How to diagnose the P0685 code

Diagnosing the P0685 code can be challenging, as it requires specialized tools and knowledge of the vehicle’s electrical system. However, there are several steps that can be taken to diagnose the code effectively even if you aren’t that experienced:

Visual inspection

The first step in diagnosing the P0685 code is to perform a visual inspection of the wiring and connectors associated with the ECM/PCM power relay circuit. This can help identify any obvious issues, such as frayed wires or corroded connectors.

Check the battery voltage

The mechanic will also check the battery voltage to ensure that it is within the proper range. If the battery voltage is too low, it can cause issues with the power relay circuit and trigger the P0685 code.

Check the wiring with continuity tests

You can also perform continuity tests on the wiring associated with the ECM/PCM power relay circuit. This can help identify any open or short circuits that could be causing the issue.

Test the ECM’s power relay

Finally, the mechanic will test the ECM/PCM power relay itself to see if it is functioning properly. This may involve using a multimeter or other specialized tools to test various components of the relay.

How to fix the P0685 code

Fixing the P0685 code will depend on the specific cause of the issue. The cost of fixing the P0685 code will also vary depending on the specific cause of the issue and the vehicle’s make and model, so let’s take a look at potential solutions:

Replace the faulty ECM power relay

If the root cause of the P0685 code is a faulty ECM/PCM power relay, then the mechanic will need to replace the relay. This usually involves removing the old relay and installing a new one in its place.

Repair wiring issues

If the issue is caused by damaged wiring, the mechanic will need to repair or replace the affected wiring. This may involve splicing in new sections of wire or replacing entire wire harnesses.

Clean the corroded connections

Corroded connectors can cause issues with the ECM/PCM power relay circuit and trigger the P0685 code. In some cases, cleaning or replacing the affected connectors can resolve the issue.

Check the battery voltage

If the battery voltage is too low, it can cause issues with the power relay circuit and trigger the P0685 code. Checking and correcting the battery voltage can sometimes resolve this issue.

How to prevent the P0685 code

Preventing the P0685 code can be challenging, as it is often caused by wear and tear on the vehicle. However, routine maintenance can help prevent the code from appearing, including the following preventive actions:

• Battery voltage inspections
• Checking the alternator
• Making sure that the ECM’s connections are in place

Additionally, drivers should be cautious when driving in extreme temperatures, as this can put extra strain on the vehicle’s electrical system. If you notice any symptoms of the P0685 code, it is important to address them as soon as possible to prevent further damage to the vehicle.

Our take

Now that you know a bit more about the code in general and how it may affect your vehicle, you can use this information to your advantage when fixing the code. We hope that this guide was helpful enough to get you on the right path when dealing with the code, and preventing it from appearing again in the future.

Make sure to check your car’s connections and the voltage of the electrical system’s performance to ensure that everything works properly with the ECM.