AutoCodes – Cadillac – P0685 Cadillac

P0685 Cadillac 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 Cadillac 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 4,272

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

What does this mean?

What are the Possible Causes of the DTC P0685 Cadillac?

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 Cadillac?

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 Cadillac 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.

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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 Cadillac Code

1. What are the common symptoms of OBDII code P0685 in a Cadillac?

The common symptoms of code P0685 in a Cadillac include engine stalling, difficulty starting the engine, and the illumination of the check engine light.

2. What could cause the Engine Control Module Power Relay Control Circuit to be open in a Cadillac?

Potential causes of an open Engine Control Module Power Relay Control Circuit in a Cadillac include a faulty relay, damaged wiring, or a malfunctioning engine control module.

3. How can I diagnose the OBDII code P0685 in my Cadillac?

To diagnose code P0685 in your Cadillac, you can start by checking the power relay, inspecting the wiring for any damage, and testing the engine control module for proper functionality.

4. Can I drive my Cadillac with OBDII code P0685?

It is not recommended to drive your Cadillac with OBDII code P0685, as it can lead to engine stalling and potential safety hazards. It is best to address the issue promptly.

5. What are some repair tips for fixing OBDII code P0685 in a Cadillac?

Repair tips for addressing code P0685 in a Cadillac include checking and replacing the power relay, repairing any damaged wiring, and, if necessary, replacing the engine control module.

6. Is it safe to reset the check engine light after fixing OBDII code P0685 in a Cadillac?

Yes, once you have fixed the issue causing code P0685 in your Cadillac, it is safe to reset the check engine light using an OBDII scanner or by disconnecting the car battery for a few minutes.

7. How much does it typically cost to fix OBDII code P0685 in a Cadillac?

The cost of fixing OBDII code P0685 in a Cadillac can vary depending on the specific cause of the issue. It may involve replacing a faulty relay, repairing wiring, or replacing the engine control module, which can range in cost.

8. Can a DIY enthusiast fix OBDII code P0685 in a Cadillac?

If you have experience working on automotive electrical systems, you may be able to fix OBDII code P0685 in a Cadillac yourself by following diagnostic procedures and making the necessary repairs carefully.

9. Will OBDII code P0685 in a Cadillac affect fuel efficiency?

Yes, OBDII code P0685 in a Cadillac can affect fuel efficiency due to engine performance issues like stalling and difficulty starting. Resolving the code promptly can help restore optimal fuel efficiency.

10. How long does it take to repair OBDII code P0685 in a Cadillac?

The time it takes to repair OBDII code P0685 in a Cadillac can vary based on the specific cause of the issue and the complexity of the repair. It may take anywhere from a few hours to a full day at a repair shop.