P0685 Technical Description
ECM/PCM Power Relay Control Circuit Open
If you’re reading this, you likely have a P0685 trouble code showing up on your car’s diagnostic system. We’ll cover what it means, symptoms, causes, and how to fix it.
I’ve seen this issue before, and it’s usually straightforward to resolve.
We’ll break down the technical definition, explain the symptoms to watch for, identify common causes, and provide step-by-step fixes. By the end, you’ll have a clear action plan
Ready to solve this problem? Let’s get into the details.
Key Takeaways
- P0685 trouble code means “ECM/PCM Power Relay Control Circuit Open.”
- Symptoms include engine not starting, stalling, poor performance, and electrical issues.
- Common causes are faulty relay, damaged wiring, loose connectors, faulty ECM/PCM, and blown fuse.
- Inspect and test the power relay and wiring to diagnose the issue.
- Replace faulty relays, repair damaged wiring, and check connectors for corrosion.
- Ensure ECM/PCM functionality to fully resolve the P0685 code.
Table of ContentsShow
What Does P0685 Trouble Code Mean?
The P0685 trouble code indicates a problem with the power relay control circuit in the Engine Control Module (ECM) or Powertrain Control Module (PCM).
In simpler terms, your car’s computer is having trouble controlling the power relay, which is crucial for powering the ECM/PCM itself.
When this code pops up, it means the circuit that controls the power relay is open. An “open circuit” means there’s a break somewhere along the path that electricity travels.
This could be due to a broken wire, a faulty relay, or a problem with the ECM/PCM itself.
The ECM/PCM is the brain of your car. It manages everything from the fuel mixture to the timing of the spark plugs.
For it to function, it needs a consistent power supply. The power relay ensures that the ECM/PCM gets this steady power.
When the relay control circuit is open, the ECM/PCM can’t operate correctly, leading to various performance issues or even preventing the car from starting.
The P0685 code can cause several symptoms, such as the engine not starting, stalling, or running poorly.
Sometimes, you might also notice electrical issues since the ECM/PCM isn’t getting the power it needs to regulate these systems.
To fix this issue, you’ll need to inspect the power relay, associated wiring, and connectors for any signs of damage or wear.
If the relay or wiring is faulty, replace them. In some cases, the problem might lie within the ECM/PCM, which would require a more detailed diagnosis and potentially a replacement of the module.
Understanding what the P0685 code means is the first step in diagnosing and fixing the problem.
With this knowledge, you can take the necessary steps to get your car back in working order.
P0685 Trouble Code Symptoms
When the P0685 code appears, you may notice the following symptoms:
- Engine not starting
- Engine stalling
- Poor engine performance
- Intermittent electrical issues
- Check Engine Light illuminated
P0685 Trouble Code Causes
Several factors can trigger the P0685 code:
- Faulty power relay
- Broken or damaged wiring in the relay control circuit
- Corroded or loose connectors
- Faulty ECM/PCM
- Blown fuse in the power relay circuit
How To Fix A P0685 Trouble Code
Fixing the P0685 trouble code requires a systematic approach to diagnose and repair the issue. Here’s a step-by-step guide to help you troubleshoot and resolve it:
1. Check the Battery and Fuses
Start by inspecting the battery and related fuses. Ensure the battery is fully charged and the fuses are intact. Replace any blown fuses and recharge or replace the battery if needed.
2. Inspect the Wiring and Connectors
Examine the wiring and connectors in the Engine Control Module (ECM) circuit for signs of damage, corrosion, or loose connections. Repair or replace any damaged components.
3. Test the Main Relay
The P0685 code often points to a problem with the ECM power relay. Use a multimeter to test the relay’s functionality. If the relay is faulty, replace it.
4. Examine the ECM
Check the ECM for any signs of damage or malfunction. This step usually requires professional diagnostic tools. If the ECM is faulty, it may need reprogramming or replacement.
5. Check for Short Circuits or Open Circuits
Use a multimeter to test for short circuits or open circuits in the ECM power supply circuit. Repair any shorts or open circuits found.
6. Clear the Code and Test Drive
After completing the necessary repairs, clear the code using an OBD-II scanner. Then, take the vehicle for a test drive to ensure the issue is resolved and the code does not reappear.
Following these steps will help you diagnose and fix the P0685 trouble code, ensuring your vehicle’s ECM receives the proper power supply and functions correctly.
Conclusion
Now you know what the P0685 trouble code means and how to fix it.
Got any questions about diagnosing or repairing this code?
Drop a comment below and share your experiences or ask for advice!
