Understanding the P0685 code
The P0685 code is an OBD-II code that indicates a problem with the ECM/PCM power relay control circuit. This code is most commonly found in Ford, Lincoln, and Mercury vehicles, but can also appear in other brands.
The ECM, or Engine Control Module, is the brain of your vehicle’s engine management system. It controls the fuel injection, ignition timing, and other critical functions that keep your engine running smoothly. The ECM relies on a steady supply of power to function properly, and that’s where the power relay control circuit comes in.
The power relay control circuit is responsible for supplying power to the ECM. It does this by controlling a relay that switches power between the battery and the ECM. When the relay is in the off position, power is cut off from the ECM, and it can’t function properly.
If the ECM/PCM power relay control circuit malfunctions, the ECM may lose power intermittently or permanently. This can cause a variety of issues, including rough idling, stalling, and poor fuel economy. In some cases, the engine may not start at all.
There are several potential causes of the P0685 code. The most common cause is a faulty relay or fuse. Other potential causes include a damaged wiring harness or a bad ECM.
One of the first steps in diagnosing the P0685 code is to check the power relay and fuse. These are relatively easy to access and can often be tested with a multimeter. If the relay or fuse is found to be faulty, it can be replaced relatively easily.
If the power relay and fuse are found to be functioning correctly, the next step is to inspect the wiring harness. Look for any visible signs of damage, such as cuts or abrasions. If any damage is found, the wiring harness will need to be repaired or replaced.
If the wiring harness is found to be in good condition, the next step is to test the ECM itself. This is a more complicated process and may require specialized equipment. If the ECM is found to be faulty, it will need to be replaced.
Overall, fixing the P0685 code can be a relatively simple or complex process, depending on the underlying issue. If you’re not experienced with vehicle repairs, it’s recommended to seek assistance from a qualified mechanic. They’ll be able to diagnose the problem and recommend the best course of action to get your vehicle running properly again.
Common causes of the P0685 code
If you’re in the middle of driving and suddenly your check engine light comes on, you might be a bit worried. The reality is that a check engine light can mean a variety of things, including a P0685 code. The P0685 code is a diagnostic trouble code that indicates a problem with the ECM/PCM power relay control circuit.
When this code is detected, it usually indicates an issue with the starter relay. A starter relay is responsible for the control of the electrical supply needed to start the engine. When a faulty starter relay becomes an issue, it means that the charging system and other power-driven instruments will also fail.
The following are some of the common reasons that trigger the P0685 code:
1. Dead Battery
A common cause for a P0685 code is a dead battery. A battery that no longer has sufficient power to support a relay can trigger this code. A dead battery can also cause low voltage problems that can lead to the ECM/PCM power relay control circuit causing the P0685 code to appear.
2. Faulty Alternator
The alternator is responsible for charging the vehicle’s battery. If the alternator is faulty, it can cause low voltage problems which affects the ECM/PCM power relay control circuit. The battery will not receive enough power for the starter relay, causing a P0685 code to appear.
Apart from the P0685 code, a bad alternator can cause the battery light on the dashboard to come on as this is one of the major components of the charging system. The battery will eventually die if it is not charged by the alternator.
3. Overcharging Battery
While an undercharged battery can cause a P0685 code, an overcharged battery can also cause the code to appear. Overcharging could be caused by a defective regulator inside the alternator, which would send excessive voltage to the battery and other parts of the electrical system, causing the P0685 code to appear.
Overcharging can also cause damage to other electrical components, which could lead to expensive auto repairs, so it is important to address an overcharging battery issue immediately.
4. Corroded Battery Terminals
Corroded battery terminals could also trigger a P0685 code. The corrosion on the battery terminals is often the result of a chemical reaction with the battery acid. The corroded battery terminals can prevent the battery from providing the required voltage to the starter relay.
If the corrosion is relatively minor, it can be removed from the terminals by cleaning them. However, if the terminals are severely corroded, they may need to be replaced entirely.
5. Malfunctioning Starter Relay
A malfunctioning starter relay causes the P0685 code to appear. The starter relay is responsible for sending power to the starter, which allows the engine to turn over. If the starter relay isn’t working correctly, it might not send a signal to the starter, leading to the P0685 code appearing.
The starter relay is an essential component for starting your vehicle so it needs to be inspected regularly, and if there are issues found, it should be replaced immediately.
These are the most common reasons for a P0685 code. If your check engine light comes on and you’re not sure what’s causing it, it’s best to have it checked out by a professional mechanic who can diagnose and fix the issue to ensure your vehicle continues to operate correctly.
Diagnosing the P0685 code
When you think your car has the P0685 code, there are several steps you can follow to diagnose the problem correctly.
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Step 1: Verify the code
The first step in diagnosing this error code is to confirm if the Check Engine or Warning Light on your car’s dashboard is, indeed, the P0685 code. If you’re not sure, you can perform a manual code readout or use a OBD-II scanner to retrieve any stored codes in your car’s computer system.
Step 2: Check the battery
The battery is a fundamental part of a car’s electrical system, and if it has low voltage or discharged, it can cause various error codes, including P0685. Check the battery voltage using a multimeter when the engine is turned off and while it’s running. If the reading is lower than 12.2 volts when the engine is off and is less than 13.5 volts when the engine is on, the battery could be faulty and need to be replaced.
Step 3: Inspect the wiring and connectors
Faulty or damaged wires are common culprits for the P0685 code. Inspect all wires connected to the PCM, the alternator, the starter, and all other components in the car’s electrical system. Look for obvious signs of damage like broken insulation, exposed wires, or loose connectors that could be causing a poor connection or shorting the circuit. Use a digital multimeter to test the continuity of each wire. Any wire that does not show continuity could be the source of the problem.
In some cases, it may be necessary to inspect the wiring harness connectors and pins for damage or corrosion. Poorly connected or corroded pins can cause electrical shorts that result in various error codes, including P0685. Use a contact cleaner and a wire brush to clean any corroded connectors.
Step 4: Check PCM Ground Circuit
The Powertrain Control Module (PCM) uses various sensors and components to regulate the car’s output. If the PCM ground circuit is not working as designed, it won’t be able to regulate the car’s output correctly, leading to the P0685 error code. To test the GROUND circuit, start by disconnecting the battery. Then, use a digital multimeter to check the resistance between the PCM’s ground terminal and the chassis. If the reading is more than 5 ohms, the ground circuit is likely faulty.
There are various ways to fix an issue with a bad PCM ground circuit, depending on exactly what is causing the problem. However, it can often be as simple as cleaning or tightening any loose connections in the circuit.
Step 5: Test the Alternator
The car’s alternator is responsible for charging the battery and powering the vehicle’s various electrical components. If it is not working correctly, it can cause the P0685 error code. To check the alternator, use a digital multimeter to test the battery voltage with the engine running. It should read around 13 to 15 volts. If the reading is less than 13 volts or more than 15 volts, the alternator could be faulty and need to be replaced. You can also check the alternator belt for any signs of wear or damage.
In conclusion, the P0685 error code indicates an issue in the car’s electrical system, and diagnosing the cause can be a bit tricky. But if you follow the above steps meticulously, you should be able to diagnose and fix the issue. Remember, although the above steps are quite easy to perform, it’s always recommended to consult a certified mechanic if you’re unsure about any diagnosis and repair steps you plan to take.
What Causes the P0685 Code and How to Fix It
The P0685 code is often caused by a problem with the powertrain control module (PCM), which is part of the vehicle’s engine computer. However, there are other potential causes that may trigger this code, such as a faulty ground connection, a damaged wiring harness, or a malfunctioning alternator. When the PCM detects a problem, it will trigger the code and illuminate the check engine light. If you’re experiencing this issue, you’ll need to diagnose the root cause and fix the problem before you can clear the code and turn off the check engine light. Follow these steps to fix the P0685 code:
Step 1: Check the Wiring Harness
The first step in fixing the P0685 code is to inspect the wiring harness that connects the PCM to the vehicle’s electrical system. Look for any signs of wear or damage, such as frayed wires or loose connections. If the wiring harness is damaged, it may be necessary to replace it. You may also need to check the ground connection between the PCM and the vehicle’s chassis, as a poor ground can lead to electrical problems. Make sure that all connections are secure and free of corrosion.
Step 2: Check the Alternator
If the wiring harness and ground connection are in good condition, you may need to check the alternator. A malfunctioning alternator can cause voltage fluctuations that can damage the PCM and trigger the P0685 code. Use a multimeter to check the voltage output of the alternator when the engine is running. The voltage should be between 13.5 and 14.5 volts. If the voltage is outside of this range, you may need to replace the alternator.
Step 3: Check the Battery
Another potential cause of the P0685 code is a weak or dead battery. Use a volt meter to check the voltage of the battery when the engine is off. The voltage should be around 12.6 volts. If the voltage is below 12 volts, you may need to recharge or replace the battery. A weak battery can cause voltage fluctuations that can trigger the P0685 code and damage the PCM.
Step 4: Replace the PCM
If none of the previous steps work, you may need to replace the PCM. This is the most expensive option, but it will typically fix the P0685 code. The PCM is responsible for controlling the engine and other systems, so if it’s malfunctioning, it can cause a range of problems. To replace the PCM, you’ll need to disconnect the battery, remove the old PCM, and install the new one. Make sure that all connections are secure and that the PCM is programmed correctly for your vehicle.
Fixing the P0685 code can be a complex process, but by following these steps, you can diagnose the problem and determine the best course of action. Whether it’s a wiring issue, a faulty alternator, or a malfunctioning PCM, it’s important to address the problem quickly to avoid further damage to your vehicle. If you’re not comfortable working on your vehicle’s electrical system, it’s best to consult a professional mechanic for assistance.
Clearing the P0685 code and verifying the repair
If you’ve been experiencing problems with your vehicle, and you’ve scanned it with an OBD-II scanner, you may have encountered the P0685 code. This code indicates that there’s an issue with the ECM/PCM power relay control circuit, which can cause a host of problems with your car’s engine and transmission.
While it can be difficult to pinpoint the exact cause of the P0685 code, there are a few steps you can take to clear the code and verify the repair. In this article, we’ll outline those steps, so you can get your car back on the road as soon as possible.
Step 1: Determine the Cause of the Problem
The first step in clearing the P0685 code and verifying the repair is to determine the cause of the problem. There are several things that can cause this code to appear, including a faulty ECM/PCM power relay control circuit, a malfunctioning PCM, or a wiring issue. To determine the cause of the problem, you may need to take your car to an auto repair shop that has specialized diagnostic equipment.
Step 2: Clear the Code
Once you’ve determined the cause of the problem and made any necessary repairs, you’ll need to clear the P0685 code from your car’s computer. To do this, you’ll need an OBD-II scanner. Simply plug the scanner into your car’s OBD-II port (usually located under the dashboard on the driver’s side), turn the ignition switch on (without starting the engine), and follow the instructions on the scanner’s display to clear the code.
Note that simply clearing the code won’t necessarily fix the underlying problem. If the code reappears, you’ll need to investigate further to determine what’s causing it.
Step 3: Verify the Repair
After clearing the P0685 code, it’s important to verify that the repair was successful. The best way to do this is to take your car for a test drive. This will allow you to see if the code reappears, or if the problem has been resolved.
If you’re still experiencing problems after clearing the code, it’s possible that there’s another issue with your car’s engine or transmission. In this case, you may need to take your car to an auto repair shop for further diagnosis.
Conclusion
The P0685 code can be a frustrating problem to deal with, but by following the steps outlined in this article, you should be able to clear the code and verify the repair. Remember, it’s important to determine the cause of the problem before attempting to fix it, and to always test your car thoroughly after making any repairs.
If you’re still experiencing problems with your car, don’t hesitate to take it to a qualified auto repair shop for further diagnosis. With the right expertise and equipment, a professional mechanic should be able to get to the bottom of any issue with your car’s engine or transmission.