AutoCodes – GMC – P0686 2015 GMC Sierra

P0686 2015 GMC Sierra Code - Engine Control Module Power Relay Control Circuit Low

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: P0686 2015 GMC Sierra indicates Engine Control Module Power Relay Control Circuit Low.
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 178

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
Cost to Diagnose
FAQs
Comments
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Code P0686 2015 GMC Sierra 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 P0686 2015 GMC Sierra - Engine Control Module Power Relay Control Circuit Low - AutoCodes.com — P0686 2015 GMC Sierra Code - Engine Control Module Power Relay Control Circuit Low

What does this mean?

What are the Possible Causes of the DTC P0686 2015 GMC Sierra?

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 P0686 2015 GMC Sierra?

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 is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0686 2015 GMC Sierra 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 P0686 2015 GMC Sierra code?

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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 P0686 2015 GMC Sierra Code

1. What does OBDII code P0686 mean on a 2015 GMC Sierra?

P0686 indicates a problem with the Engine Control Module (ECM) Power Relay Control Circuit being too low, meaning the ECM may not be receiving sufficient power.

2. What are the common symptoms of code P0686 on a 2015 GMC Sierra?

Common symptoms include difficulty starting the engine, engine stalling, reduced fuel efficiency, and illuminated check engine light.

3. What causes code P0686 on a 2015 GMC Sierra?

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

4. Can I drive my 2015 GMC Sierra with code P0686 active?

Driving with code P0686 is not recommended, as it can lead to engine stalling or prevent the engine from starting, potentially causing unsafe driving conditions.

5. How is code P0686 diagnosed on a 2015 GMC Sierra?

A technician will use a scan tool to confirm the code, inspect the ECM power relay, check for damaged wiring or connectors, and test the power and ground circuits.

6. What repairs can fix code P0686 on a 2015 GMC Sierra?

Repairs may include replacing the ECM power relay, repairing damaged wiring or connectors, replacing a blown fuse, or, in rare cases, replacing the ECM itself.

7. How much does it cost to fix code P0686 on a 2015 GMC Sierra?

Repair costs vary depending on the issue but typically range from $50 to $300, with relay replacements being on the lower end and ECM replacements on the higher end.

8. Can a bad battery cause code P0686 on a 2015 GMC Sierra?

Yes, a weak or failing battery can cause low voltage in the ECM power relay circuit, triggering code P0686.

9. How can I prevent code P0686 from recurring on my 2015 GMC Sierra?

Regularly inspect the wiring and connections for corrosion or damage, ensure the battery is in good condition, and replace the ECM power relay if it shows signs of wear.

10. Will disconnecting the battery clear code P0686 on a 2015 GMC Sierra?

Disconnecting the battery may temporarily clear the code, but it wonâ€™t fix the underlying issue, and the code is likely to return until the problem is resolved.