AutoCodes – GMC – P0686 GMC

P0686 GMC 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 GMC 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 2,309

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 GMC 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 GMC - Engine Control Module Power Relay Control Circuit Low - AutoCodes.com — P0686 GMC Code - Engine Control Module Power Relay Control Circuit Low

What does this mean?

What are the Possible Causes of the DTC P0686 GMC?

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 GMC?

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 GMC 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 GMC code?

Need more information on how to fix the P0686 GMC code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P0686 GMC code diagnosed by a professional: Find a repair shop in your area

Information for Specific GMC Models

P0686 2014 GMC Sierra — Engine Control Module Power Relay Control Circuit Low
P0686 2015 GMC Sierra — Engine Control Module Power Relay Control Circuit Low
P0686 2016 GMC Sierra — Engine Control Module Power Relay Control Circuit Low
P0686 2017 GMC Sierra — Engine Control Module Power Relay Control Circuit Low
P0686 2018 GMC Sierra — Engine Control Module Power Relay Control Circuit Low

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 GMC Code

1. What are the common symptoms of OBDII code P0686 in a GMC vehicle?

The common symptoms of OBDII code P0686 in a GMC vehicle may include engine stalling, rough idling, difficulty starting the engine, and decreased fuel efficiency.

2. What can cause the Engine Control Module Power Relay Control Circuit Low code P0686 in a GMC vehicle?

The P0686 code in a GMC vehicle is usually caused by a faulty engine control module power relay, poor electrical connections, a damaged relay control circuit, or a defective engine control module.

3. How can I diagnose the OBDII code P0686 in my GMC vehicle?

Diagnosing the P0686 code in a GMC vehicle involves using an OBDII scanner to retrieve the trouble code, inspecting the engine control module power relay and related wiring for any damage, and testing the relay control circuit for proper voltage and continuity.

4. Can I still drive my GMC vehicle with the P0686 trouble code?

It is not recommended to drive your GMC vehicle with the P0686 trouble code present, as it can lead to potential engine performance issues and further damage if left unresolved.

5. What are some repair tips for fixing the P0686 code in a GMC vehicle?

Repair tips for addressing the P0686 code in a GMC vehicle include checking and replacing the engine control module power relay if necessary, repairing any damaged wiring or connections, and clearing the trouble code after completing the repairs.

6. How much does it cost to fix the P0686 code in a GMC vehicle?

The cost of fixing the P0686 code in a GMC vehicle can vary depending on the underlying cause of the issue, the cost of parts needed for repair, and labor charges. It is recommended to consult with a professional mechanic for an accurate cost estimate.

7. Can a DIY enthusiast repair the P0686 code in a GMC vehicle?

While some DIY enthusiasts may be able to address the P0686 code by following repair guides and using the necessary tools, it is recommended to consult with a professional mechanic for proper diagnosis and repair to ensure the issue is fully resolved.

8. Will resetting the trouble code make the P0686 issue go away permanently?

Simply resetting the trouble code associated with the P0686 issue may temporarily clear the warning light, but it will not resolve the underlying problem causing the code to reappear. It is essential to diagnose and fix the root cause of the issue to prevent future occurrences.

9. Is the P0686 code specific to GMC vehicles only?

The OBDII code P0686 related to the Engine Control Module Power Relay Control Circuit Low is not specific to GMC vehicles only. It can appear in various makes and models, so it is essential to consult the vehicle's specific diagnostic manual for accurate information.

10. Can a faulty battery or alternator trigger the P0686 trouble code in a GMC vehicle?

While a faulty battery or alternator can cause electrical issues in a vehicle, they are not common triggers for the P0686 trouble code specifically. It is best to focus on diagnosing the engine control module power relay and related components when addressing the P0686 code in a GMC vehicle.