AutoCodes – Chevrolet – P0685 2017 Chevrolet Silverado

P0685 2017 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 2017 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 478

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 2017 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 2017 Chevrolet Silverado - Engine Control Module Power Relay Control Circuit Open - AutoCodes.com — P0685 2017 Chevrolet Silverado Code - Engine Control Module Power Relay Control Circuit Open

What does this mean?

What are the Possible Causes of the DTC P0685 2017 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 2017 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 2017 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 2017 Chevrolet Silverado code?

Need more information on how to fix the P0685 2017 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 2017 Chevrolet Silverado Code

1. What does OBDII code P0685 mean on a 2017 Chevrolet Silverado?

P0685 indicates an open circuit in the Engine Control Module (ECM) Power Relay Control Circuit, meaning the ECM may not be receiving the proper power supply.

2. What are the common symptoms of code P0685 in a 2017 Chevy Silverado?

Symptoms may include the engine not starting, stalling while driving, no communication with the ECM, or the Check Engine Light being illuminated.

3. What causes the P0685 code to appear on a 2017 Chevrolet Silverado?

Common causes include a faulty ECM power relay, damaged wiring or connectors in the power relay circuit, a blown fuse, or a malfunctioning ECM.

4. How can I diagnose the P0685 code on my Silverado?

Start by inspecting the ECM power relay, checking for blown fuses, and examining the wiring and connectors for damage or corrosion. Use a multimeter to test voltage and continuity in the circuit.

5. Can a faulty ECM power relay cause the P0685 code?

Yes, a malfunctioning ECM power relay is a common cause of this code, as it can prevent proper power delivery to the ECM.

6. Is it safe to drive my 2017 Chevrolet Silverado with the P0685 code?

It is not recommended to drive with this code, as it may cause the engine to stall unexpectedly or fail to start, potentially leaving you stranded.

7. How do I fix the P0685 code on my Silverado?

Repairs may include replacing the ECM power relay, repairing or replacing damaged wiring or connectors in the circuit, replacing blown fuses, or, in rare cases, replacing the ECM.

8. How much does it cost to fix the P0685 code on a 2017 Chevy Silverado?

Repair costs vary depending on the issue. Replacing an ECM power relay typically costs $20â€“$50 for the part, while wiring repairs or ECM replacement can be significantly more expensive.

9. Can a weak battery trigger the P0685 code?

While unlikely, a weak or failing battery can sometimes cause electrical issues, so itâ€™s worth checking the battery and charging system if the code persists.

10. Do I need to reprogram the ECM after fixing the P0685 code?

In most cases, reprogramming is not required, but if the ECM itself is replaced, it will need to be programmed to match your vehicle's specifications.