P0685 2018 Chevrolet Silverado Code - Engine Control Module Power Relay Control Circuit Open
Quick Answer
The P0685 diagnostic trouble code (DTC) for a 2018 Chevrolet Silverado indicates a problem with the Engine Control Module (ECM) Power Relay Control Circuit being open. Common causes include Faulty Power Relay: A malfunctioning power relay can cause an open circuit and prevent power from reaching the ECM, Wiring Issues: Damaged or corroded wiring connections between the power relay and ECM can disrupt the circuit, ECM Failure: A faulty ECM itself can also be the root cause of the P0685 code, requiring replacement. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
- What it means
- P0685 2018 Chevrolet Silverado indicates Engine Control Module Power Relay Control Circuit Open.
- Common causes
- Common causes include Faulty Power Relay: A malfunctioning power relay can cause an open circuit and prevent power from reaching the ECM, Wiring Issues: Damaged or corroded wiring connections between the power relay and ECM can disrupt the circuit, ECM Failure: A faulty ECM itself can also be the root cause of the P0685 code, requiring replacement.
- Severity
- High - diagnose this code as soon as possible.
- Can I drive?
- Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
Fix Your Car Smarter
Try the New AutoCodes App!
Get complete OBDII diagnostics, repair solutions, and cost estimates, plus AI chat support on demand.
Code P0685 2018 Chevrolet Silverado Description
The P0685 diagnostic trouble code (DTC) for a 2018 Chevrolet Silverado indicates a problem with the Engine Control Module (ECM) Power Relay Control Circuit being open. The ECM, also known as the engine control unit (ECU), is a crucial component that manages various engine functions, such as fuel injection, ignition timing, and emissions control. The power relay control circuit is responsible for providing power to the ECM, allowing it to function properly. When this circuit is open, it means that there is a break or interruption in the electrical connection between the power relay and the ECM.
Common Causes of P0685 2018 Chevrolet Silverado
- Faulty Power Relay: A malfunctioning power relay can cause an open circuit and prevent power from reaching the ECM.
- Wiring Issues: Damaged or corroded wiring connections between the power relay and ECM can disrupt the circuit.
- ECM Failure: A faulty ECM itself can also be the root cause of the P0685 code, requiring replacement.
- Loose Connections: Loose or poor connections at the power relay or ECM can lead to an open circuit.
- Electrical Short: An electrical short in the circuit can cause the power relay control circuit to be open.
Symptoms of P0685 2018 Chevrolet Silverado
- Check Engine Light: The most common symptom associated with the P0685 code is the illumination of the check engine light on the vehicle's dashboard.
- Engine Stalling: The engine may stall unexpectedly or have difficulty starting due to the lack of power to the ECM.
- Reduced Performance: The vehicle may experience a decrease in performance, such as sluggish acceleration or rough idling.
- Poor Fuel Efficiency: An open circuit in the power relay control can lead to increased fuel consumption and decreased fuel efficiency.
- Transmission Issues: The vehicle may exhibit transmission shifting problems or erratic behavior due to communication issues with the ECM.
How to Fix P0685 2018 Chevrolet Silverado
- Diagnose the Issue: Use a diagnostic scanner to retrieve the trouble code and perform a thorough inspection of the power relay control circuit and related components.
- Check Power Relay: Test the power relay for proper operation and replace it if necessary.
- Inspect Wiring: Check the wiring harness for any damage, corrosion, or loose connections, and repair or replace as needed.
- Test ECM: Verify the functionality of the ECM by testing its power supply and communication with other vehicle systems.
- Clear Codes: After completing the repairs, clear the DTC using a diagnostic scanner and test drive the vehicle to ensure the issue has been resolved.
Cost to Fix P0685 2018 Chevrolet Silverado
The typical repair costs for addressing a P0685 code on a 2018 Chevrolet Silverado can range from $150 to $500, depending on the specific cause of the issue and the extent of repairs needed. This estimate includes the cost of parts, such as a new power relay or wiring harness, as well as labor charges for diagnosis and repair. It's important to note that actual costs may vary based on factors such as the location of the repair shop, the expertise of the technician, and any additional components that may need to be replaced. It is recommended to consult with a qualified mechanic or dealership for a more accurate cost estimate based on your vehicle's specific needs.
Tech Notes for P0685 2018 Chevrolet Silverado
Need more information about the P0685 2018 Chevrolet Silverado code?
Need more information on how to fix the P0685 2018 Chevrolet Silverado code? Get Access to Factory Service Manuals
Need Help with the Code?
Get the P0685 2018 Chevrolet Silverado code diagnosed by a professional: Find a repair shop in your area
Frequently Asked Questions about P0685 2018 Chevrolet Silverado Code
1. What does the OBDII code P0685 mean on a 2018 Chevrolet Silverado?
P0685 indicates an "Engine Control Module (ECM) Power Relay Control Circuit Open," meaning there’s an issue with the circuit controlling the ECM power relay.
2. What are the common symptoms of code P0685 on a 2018 Silverado?
Symptoms may include engine stalling, failure to start, intermittent power issues, or an illuminated check engine light.
3. What causes the P0685 code to appear on a 2018 Chevrolet Silverado?
Common causes include a faulty ECM power relay, damaged wiring or connectors in the circuit, a blown fuse, or a malfunctioning ECM.
4. Can I drive my 2018 Silverado with a P0685 code?
Driving with this code is not recommended, as the engine may stall unexpectedly or fail to restart, posing safety risks.
5. How do I diagnose a P0685 code on a 2018 Chevrolet Silverado?
Start by checking the ECM power relay, related fuses, and wiring for damage or loose connections. Use a multimeter to test for proper voltage in the circuit.
6. How do I fix a P0685 code on my 2018 Silverado?
Repairs may involve replacing a faulty ECM power relay, repairing damaged wiring, replacing a blown fuse, or in rare cases, replacing the ECM itself.
7. How much does it cost to fix a P0685 code on a 2018 Chevrolet Silverado?
Repair costs can vary, but replacing the ECM power relay typically costs $50–$150, while more extensive electrical repairs or ECM replacement may exceed $500.
8. Can a dead battery cause the P0685 code on my Silverado?
A weak or dead battery can sometimes trigger electrical issues, but it’s more likely caused by a fault in the ECM power relay circuit.
9. Will clearing the P0685 code with a scanner fix the problem?
Clearing the code may temporarily turn off the check engine light, but the underlying issue in the ECM power relay circuit must be fixed to prevent the code from returning.
10. Is the P0685 code related to other OBDII codes on a 2018 Silverado?
Yes, it may be accompanied by other codes related to the ECM, such as P0686 or P0687, which indicate additional issues in the ECM power relay circuit.
Discuss the causes and fixes for P0685 2018 Chevrolet Silverado OBDII Code
Code P0685 2018 Chevrolet Silverado comments
No comments found for this page.
Fix Your Car Smarter
Try the New AutoCodes App!
Get complete OBDII diagnostics, repair solutions, and cost estimates, plus AI chat support on demand.