You’ve got a P0685 code and want to fix it quickly? Here’s how to get it done.
First, check the ECM/PCM power relay, wiring, and connectors for any obvious damage or rust.
Use a multimeter to test the relay and check the battery voltage to make sure there’s a proper power supply and circuit connection.
Replace any damaged parts you find right away.
Regularly cleaning connections and using dielectric grease can help prevent this OBD2 Codes issue in the future.
Want to get your car back on the road without any extra fuss? Follow these steps to pinpoint the problem and fix it fast.
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Key Takeaways
- Look at the ECM/PCM power relay and swap it out if it’s broken or damaged.
- Fix any wiring in the power relay circuit that’s damaged or rusty.
- Make sure all electrical connections are tight and free of rust.
- Check the battery voltage; if it’s not between 12.4V and 12.7V, get a new battery.
What Is the P0685 Code?
The P0685 code means there’s a problem with the power relay control circuit for your car’s Engine Control Module (ECM) or Powertrain Control Module (PCM).
This issue can mess with your engine and transmission, causing stalling, bad fuel mileage, and trouble starting your car.
When this code shows up, it points to a problem in the electrical system that controls the ECM or PCM.
To fix it, you’ll need to check the wiring, connectors, and the relay.
It’s important to diagnose the issue correctly to get your car running smoothly again.
Importance of Addressing P0685
If you ignore the P0685 code, your engine could run poorly and you might end up with some expensive repairs. Over time, this issue can cause major engine damage, lower your gas mileage, and make your car idle unevenly.
Fixing the P0685 code right away can help you avoid these problems. You’ll need to use diagnostic tools to find out what’s wrong. Start by looking at the wiring and connectors, then test the ECM/PCM power relay.
Also, check the battery voltage and do continuity tests on the circuits. Fixing the problem early keeps your engine running well and saves you money, so it’s important to act quickly.
Common Symptoms
If your car is stalling, getting worse gas mileage, or having trouble starting, these could be signs of the P0685 code. These problems can seriously affect how well your car runs and how reliable it is. By looking at these symptoms, you can figure out how your car’s performance is being affected.
Common signs to watch for:
- Engine stalling: The engine might suddenly turn off while you’re driving.
- Poor fuel economy: You may notice that your car is using more gas than usual.
- Hard starting: The engine might take longer to start or not start at all.
Noticing these symptoms early can help you fix the P0685 code quickly and prevent more damage to your car’s electrical systems.
Typical Causes
Common reasons for the P0685 code include a bad ECM/PCM power relay and damaged wiring or connectors in the power relay circuit.
Different types of relays can wear out over time, leading to electrical problems. A malfunctioning ECM or PCM might also be the culprit.
Additionally, poor electrical connections and corrosion can mess up the circuit and trigger the code.
Don’t ignore issues like a dead battery or a faulty alternator, as they can also contribute to the problem.
Thoroughly inspecting these components will help you find the exact cause. Fixing these common issues can resolve the P0685 code and get your vehicle running smoothly again.
Affected Car Models
Some car models are more likely to have the P0685 code, which makes it important to know which vehicles are commonly affected. This way, you can take steps to prevent issues and spot symptoms early.
- Honda Civic: Often has problems with the power relay for the engine control module (ECM) or powertrain control module (PCM).
- Dodge RAM: Known for failures in the relay circuit, especially in certain models.
- Ford F-150: Frequently faces the same relay issues as the Civic.
These models are some of the most affected by the P0685 code, so it’s important to stay alert if you own one.
Fixing the issue early can save you from expensive repairs and long downtime.
Visual Inspection Steps
Start your visual check by looking closely at the ECM/PCM power relay and the wires around it for any signs of damage or rust. Use a good flashlight and a magnifying glass to help you spot problems. Look for frayed wires, broken connectors, or any discoloration that could mean overheating.
| Inspection Step | What to Look For |
|---|---|
| ECM/PCM Relay | Any physical damage or burn marks. |
| Wiring | Frayed or broken wires. |
| Connectors | Make sure they are secure and not rusty. |
| Relay Contacts | Check that they are clean and not damaged. |
| Harness | Look for wear and tear or any damage. |
Testing Battery Voltage
After you’ve inspected the battery, the next thing to do is test its voltage to make sure it’s in the right range. A healthy battery is crucial because voltage issues can cause misdiagnosis.
Use a multimeter to get an accurate reading. Here’s how to do it:
- Make sure the engine is off: Also, turn off all electrical components.
- Set the multimeter to DC volts: Choose the 20V setting.
- Check the battery terminals: Put the positive lead on the positive terminal and the negative lead on the negative terminal.
If the voltage is outside this range, you might need to look into it further or replace the battery. This step helps rule out battery-related causes of the P0685 code.
Checking Wiring Circuits
Checking Wiring Circuits
To make sure the wiring circuits are in good shape, start by visually checking all the connections for any damage, rust, or wear. Look over the wiring harness carefully to ensure the cables are secure and not frayed. Use a multimeter to test for continuity and make sure the circuit is complete.
| Step | Action |
|---|---|
| 1 | Disconnect the battery |
| 2 | Visually inspect the wiring harness |
| 3 | Use a multimeter to check continuity |
| 4 | Look for signs of rust or corrosion |
| 5 | Tighten any loose connections |
Pay special attention to the connectors and terminals, as rust can mess up the circuit. Make sure all connections are tight and secure. This careful inspection can help you spot problems early, avoiding issues with the ECM/PCM power relay.
Relay and ECM Testing
Testing the Relay and ECM
After confirming all the wiring circuits are good, the next step is to test the relay and ECM to find any issues. Here’s how you can do that:
- Check the Relay:
- Use a multimeter to make sure the relay isn’t open or shorted.
- Confirm the relay is getting the right voltage.
- Inspect the ECM:
- Make sure all the input and output signals are within the required ranges.
- Verify the ECM is getting proper power and ground connections.
Following these steps will help you identify the problem causing the P0685 code more easily.
Repair and Maintenance Tips
When dealing with the P0685 code, make sure all electrical connections are clean and tight to avoid future problems.
Start by carefully checking your vehicle’s electrical systems. Look for any signs of rust or loose connections and clean them thoroughly.
Regular maintenance is important; regularly check and tighten all electrical connectors to prevent issues. Replace any damaged wiring or faulty parts right away.
Using dielectric grease on connectors can help stop rust. Regularly test your battery and alternator to make sure they’re working properly.
Keeping your vehicle’s electrical systems in good shape can save you from expensive repairs and prevent the P0685 code from coming back.
Keep a multimeter handy for regular checks and stay on top of your maintenance.
More OBD-II Codes
Frequently Asked Questions
Can a Loose Battery Terminal Cause the P0685 Code?
Yes, a loose battery terminal can cause the P0685 code. Make sure the battery connections are tight and check for other electrical problems that could be affecting the ECM/PCM power relay control circuit.
How Do I Reset the Ecm/Pcm After Fixing the P0685 Code?
To reset the ECM/PCM after fixing the P0685 code, you can disconnect the car battery for 15 minutes and then reconnect it. Another option is to use diagnostic tools for a professional ECM reset or PCM reprogramming to make sure everything works correctly.
What Tools Are Needed to Diagnose the P0685 Code?
You’ll need diagnostic scanners and multimeters to check for error codes and test circuits. Look at the wiring for any visible damage and use continuity tests to check if the electrical connections are good. You might also need special tools to test the ECM/PCM power relay accurately.
Will a Generic OBD-II Scanner Detect the P0685 Code?
Yes, your basic OBD-II scanner can detect the P0685 code. It’s made to work with OBD-II systems and read codes, helping you find and fix problems with the ECM/PCM power relay control circuit.
How Long Does It Take to Fix the P0685 Code?
It usually takes about 1 to 3 hours to fix the P0685 code. You’ll need to do some detailed troubleshooting, like looking for obvious issues, checking electrical connections, and testing the relay to make sure you find and fix the problem accurately.
Conclusion
Got a P0685 code? Don’t worry.
Grab your multimeter, check the relays, and inspect the wiring.
If you find any damage, replace the parts quickly.
A little maintenance can make a big difference.
Plus, working on your car can be pretty satisfying!
