AutoCodes – Buick – P0685 Buick

P0685 Buick 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 Buick 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 2,914

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

What does this mean?

What are the Possible Causes of the DTC P0685 Buick?

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 Buick?

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 Buick 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 Buick 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 P0685 Buick Code

1. What are the common symptoms of OBDII code P0685 in a Buick related to the Engine Control Module Power Relay Control Circuit Open?

- Common symptoms include engine stalling, difficulty starting the vehicle, and in some cases, the engine may not start at all.

2. What are the possible causes of OBDII code P0685 in a Buick related to the Engine Control Module Power Relay Control Circuit Open?

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

3. How can I diagnose OBDII code P0685 in a Buick related to the Engine Control Module Power Relay Control Circuit Open?

- Diagnosis typically involves checking the power relay, inspecting the wiring and connectors for any damage, and testing the engine control module for proper function.

4. What are some repair tips for resolving OBDII code P0685 in a Buick related to the Engine Control Module Power Relay Control Circuit Open?

- Repair tips may include replacing the faulty power relay, repairing any damaged wiring or connectors in the circuit, or replacing the engine control module if necessary.

5. Can OBDII code P0685 in a Buick related to the Engine Control Module Power Relay Control Circuit Open cause any long-term damage to the vehicle?

- If left unresolved, this code can potentially lead to further damage to the engine control module or other related components, so it is important to address the issue promptly.

6. Is it safe to continue driving my Buick with OBDII code P0685 related to the Engine Control Module Power Relay Control Circuit Open?

- It is not recommended to continue driving the vehicle with this code present, as it can cause potential reliability issues and may lead to more severe problems if not addressed.

7. How much does it typically cost to repair OBDII code P0685 in a Buick related to the Engine Control Module Power Relay Control Circuit Open?

- The cost of repair can vary depending on the exact cause of the issue, but it may range from a few hundred to a thousand dollars, including parts and labor.

8. Can I reset the OBDII code P0685 in my Buick related to the Engine Control Module Power Relay Control Circuit Open on my own?

- While you can clear the code with an OBDII scanner, it is important to diagnose and address the underlying issue causing the code before resetting it to prevent it from reoccurring.

9. Will disconnecting the battery reset OBDII code P0685 in my Buick related to the Engine Control Module Power Relay Control Circuit Open?

- Disconnecting the battery may clear the code temporarily, but it is not a permanent solution as the underlying issue still needs to be diagnosed and repaired.

10. Can a mechanic easily fix OBDII code P0685 in a Buick related to the Engine Control Module Power Relay Control Circuit Open?

- A qualified mechanic with experience in automotive electrical systems should be able to diagnose and repair this issue effectively to resolve the code.