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

Quick Answer

The P0685 diagnostic trouble code for Cadillac vehicles indicates an issue with the Engine Control Module (ECM) power relay control circuit being open. Common causes include Damaged wiring or connectors in the power relay control circuit, Faulty power relay, Blown fuse related to ECM power. 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 Damaged wiring or connectors in the power relay control circuit, Faulty power relay, Blown fuse related to ECM power.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 11, 2024
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Code P0685 Cadillac Description

The P0685 diagnostic trouble code for Cadillac vehicles indicates an issue with the Engine Control Module (ECM) power relay control circuit being open. The ECM power relay is responsible for providing power to the ECM, which is the brain of the vehicle's engine management system. The ECM controls various functions of the engine, including fuel injection, ignition timing, and emissions control. When the power relay control circuit is open, it means that there is a break or interruption in the circuit that prevents the ECM from receiving power or functioning properly.

OBDII Code P0685 Cadillac - Engine Control Module Power Relay Control Circuit Open
P0685 Cadillac Code - Engine Control Module Power Relay Control Circuit Open

Common Causes of P0685 Cadillac

  1. Damaged wiring or connectors in the power relay control circuit
  2. Faulty power relay
  3. Blown fuse related to ECM power
  4. Malfunctioning ECM
  5. Corrosion or poor connections in the circuit

Symptoms of P0685 Cadillac

  1. Engine stalling or rough idling
  2. Difficulty starting the engine
  3. Reduced engine performance
  4. Check engine light illuminated
  5. Vehicle going into "limp mode"

How to Fix P0685 Cadillac

  1. Diagnose the specific cause of the open circuit by inspecting wiring, connectors, fuses, and the power relay.
  2. Repair or replace damaged wiring or connectors in the power relay control circuit.
  3. Test and replace the faulty power relay if necessary.
  4. Check and replace any blown fuses related to ECM power.
  5. If the ECM is determined to be faulty, it may need to be replaced or reprogrammed.

Cost to Fix P0685 Cadillac

The typical repair costs for addressing an Engine Control Module Power Relay Control Circuit Open issue can vary depending on the specific cause and the labor rates at the auto repair shop. In general, the cost of parts for this repair can range from $50 to $200, while labor costs can range from $100 to $300. Overall, the total cost of the repair may fall between $150 and $500. It's important to keep in mind that labor rates can vary based on location, vehicle make and model, and the expertise of the technician. It's recommended to obtain a detailed estimate from a qualified mechanic before proceeding with the repair.

What does this mean?

Tech Notes for P0685 Cadillac

Check all the Engine Control Module (ECM) fuses, if the fuses are OK, then replacing the ECM relay should take care of the problem.

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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.

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