AutoCodes – Chevrolet – P0685 Chevrolet

P0685 Chevrolet Code - Engine Control Module Power Relay Control Circuit Open

Quick Answer

The powertrain relay is a normally open relay. Common causes include Weak battery, Low voltage while cranking, Faulty Engine Control Module (ECM) power relay. 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 Chevrolet indicates Engine Control Module Power Relay Control Circuit Open.
Common causes: Common causes include Weak battery, Low voltage while cranking, Faulty Engine Control Module (ECM) power relay.
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.

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Code Popularity 13,668

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jul 18, 2022

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0685 Chevrolet Description

The powertrain relay is a normally open relay. The relay armature is held in the open position by spring tension. Battery positive voltage is supplied directly to the relay coil and the armature contact at all times. The Engine Control Module (ECM) supplies the ground path to the relay coil control circuit via an internal integrated circuit called an Output Driver Module (ODM). The ODM output control is configured to operate as a low side driver for the powertrain relay. The ODM for the powertrain relay also incorporates a fault detection circuit, which is continuously monitored by the ECM. When the ECM commands the powertrain relay ON, ignition 1 voltage is supplied to the ECM, and to several additional circuits.

OBDII Code P0685 Chevrolet - Engine Control Module Power Relay Control Circuit Open - AutoCodes.com — P0685 Chevrolet Code - Engine Control Module Power Relay Control Circuit Open

What does this mean?

What are the Possible Causes of the DTC P0685 Chevrolet?

Weak battery
Low voltage while cranking
Faulty Engine Control Module (ECM) power relay
ECM power relay harness is open or shorted
ECM power relay circuit poor electrical connection
Blown ECM fuse
Faulty ECM

How to Fix the DTC P0685 Chevrolet?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

Check all the Engine Control Module (ECM) fuses, if the fuses are OK, then replacing the ECM relay should take care of the problem.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0685 Chevrolet code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

Need more information about the P0685 Chevrolet code?

Need more information on how to fix the P0685 Chevrolet code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P0685 Chevrolet code diagnosed by a professional: Find a repair shop in your area

Information for Specific Chevrolet Models

P0685 2014 Chevrolet Silverado — Engine Control Module Power Relay Control Circuit Open
P0685 2015 Chevrolet Silverado — Engine Control Module Power Relay Control Circuit Open
P0685 2016 Chevrolet Silverado — Engine Control Module Power Relay Control Circuit Open
P0685 2017 Chevrolet Silverado — Engine Control Module Power Relay Control Circuit Open
P0685 2018 Chevrolet Silverado — Engine Control Module Power Relay Control Circuit Open

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0685 Chevrolet Code

1. What are the common symptoms of OBDII code P0685 in a Chevrolet vehicle?

- Common symptoms include engine stalling, difficulty starting the engine, poor engine performance, and illuminated Check Engine Light.

2. What does the OBDII code P0685 on a Chevrolet indicate?

- The code P0685 indicates a problem with the Engine Control Module Power Relay Control Circuit being open.

3. What are the possible causes of the OBDII code P0685 in a Chevrolet?

- Possible causes include a faulty engine control module relay, damaged wiring or connectors in the relay circuit, or a malfunctioning engine control module.

4. How can I diagnose the cause of OBDII code P0685 in my Chevrolet?

- You can start by checking the engine control module relay for proper operation, inspecting the wiring and connectors for any damage, and testing the engine control module for faults using a diagnostic scanner.

5. Can I still drive my Chevrolet with OBDII code P0685?

- It is not recommended to drive your vehicle with code P0685 as it can lead to engine performance issues and potential stalling, which can compromise safety.

6. How can I repair OBDII code P0685 in my Chevrolet?

- Repair methods may include replacing the faulty engine control module relay, repairing damaged wiring or connectors, or replacing the engine control module if necessary.

7. Are there any DIY tips for troubleshooting OBDII code P0685 in a Chevrolet?

- You can start by checking the relay and its connections for any obvious signs of damage and ensuring they are securely connected. However, for a more accurate diagnosis, professional help may be needed.

8. Can a weak battery cause OBDII code P0685 to trigger in a Chevrolet?

- Yes, a weak or failing battery can sometimes cause voltage fluctuations that may trigger code P0685. It is recommended to check the battery's condition as part of the diagnostic process.

9. How long does it typically take to repair OBDII code P0685 in a Chevrolet?

- The repair time can vary depending on the exact cause of the code and the availability of parts. It can range from a quick relay replacement to a more involved repair involving the engine control module.

10. Will resetting the Check Engine Light make OBDII code P0685 go away?

- Resetting the Check Engine Light may temporarily turn it off, but if the underlying issue causing code P0685 is not addressed, the light is likely to come back on once the problem is detected again.