AutoCodes – Chevrolet – P0685 2018 Chevrolet Silverado

P0685 2018 Chevrolet Silverado 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 2018 Chevrolet Silverado 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 408

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 19, 2022

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0685 2018 Chevrolet Silverado 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 2018 Chevrolet Silverado - Engine Control Module Power Relay Control Circuit Open - AutoCodes.com — P0685 2018 Chevrolet Silverado Code - Engine Control Module Power Relay Control Circuit Open

What does this mean?

What are the Possible Causes of the DTC P0685 2018 Chevrolet Silverado?

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 2018 Chevrolet Silverado?

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 2018 Chevrolet Silverado 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 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?

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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 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 thereâ€™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 $50â€“$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 itâ€™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.