AutoCodes – Mazda – P0685 Mazda

P0685 Mazda Code - Engine Control Module Power Relay Control Circuit Open

Quick Answer

The Engine Control Module (ECM) monitors the power inputs. Common causes include Faulty Engine Control Module (ECM) power relay, ECM power relay harness is open or shorted, ECM power relay circuit poor electrical connection. 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 Mazda indicates Engine Control Module Power Relay Control Circuit Open.
Common causes: Common causes include Faulty Engine Control Module (ECM) power relay, ECM power relay harness is open or shorted, ECM power relay circuit poor electrical connection.
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 25,417

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 May 05, 2019

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0685 Mazda Description

The Engine Control Module (ECM) monitors the power inputs. The ECM sets the OBDII code when the ECM remains powered up after the ignition switch has been turned OFF.

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

What does this mean?

What are the Possible Causes of the DTC P0685 Mazda?

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 Mazda?

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 Mazda 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 Mazda 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 Mazda Code

1. What does the OBDII code P0685 mean on a Mazda?

P0685 indicates an issue with the Engine Control Module (ECM) Power Relay Control Circuit, specifically that the circuit is open or not functioning properly.

2. What are the common symptoms of a P0685 code on a Mazda?

Symptoms may include the engine not starting, stalling while driving, reduced engine performance, and the Check Engine Light illuminating.

3. What causes the P0685 code to appear on a Mazda?

Common causes include a faulty ECM power relay, damaged or corroded wiring, a blown fuse, or a defective Engine Control Module (ECM).

4. Can I drive my Mazda with a P0685 code?

Itâ€™s not recommended to drive with this code as it could lead to engine stalling, which may pose safety risks.

5. How do I diagnose the P0685 code on a Mazda?

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

6. What repairs are needed to fix the P0685 code on a Mazda?

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

7. How much does it cost to fix a P0685 code on a Mazda?

Costs vary depending on the issue but typically range from $50-$200 for relay or wiring repairs, and up to $1,000 or more if the ECM needs replacement.

8. Can a dead battery cause the P0685 code on a Mazda?

A dead or weak battery can sometimes trigger electrical issues, but itâ€™s more likely related to the power relay or circuit.

9. Will clearing the P0685 code fix the problem?

Clearing the code without addressing the underlying issue will not fix the problem, and the code is likely to return.

10. Can the P0685 code be caused by a software issue in the ECM?

While rare, a software glitch in the ECM can cause this code. Updating or reprogramming the ECM may resolve the issue if no hardware problems are found.