P0685 2018 GMC Sierra 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 2018 GMC Sierra 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.
Code P0685 2018 GMC Sierra Description
What are the Possible Causes of the DTC P0685 2018 GMC Sierra?
- 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 2018 GMC Sierra?
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.
Code Tech Notes
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the P0685 2018 GMC Sierra 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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Frequently Asked Questions about P0685 2018 GMC Sierra Code
What does the OBDII code P0685 mean on a 2018 GMC Sierra?
P0685 indicates an issue with the Engine Control Module (ECM) Power Relay Control Circuit, specifically an open circuit preventing proper power delivery to the ECM.
What are common symptoms of the P0685 code on a 2018 GMC Sierra?
Symptoms include difficulty starting the engine, stalling, reduced engine performance, and the check engine light being illuminated.
What causes the P0685 code on a 2018 GMC Sierra?
Common causes include a faulty ECM power relay, damaged wiring or connectors in the control circuit, or a malfunctioning ECM.
Can I still drive my 2018 GMC Sierra with a P0685 code?
Driving with a P0685 code is not recommended as it can lead to stalling and unreliable engine operation, potentially leaving you stranded.
How do I diagnose the P0685 code on a 2018 GMC Sierra?
Diagnosis typically involves inspecting the ECM power relay, checking for damaged wiring or loose connections, and testing the power circuit with a multimeter.
How do you fix the P0685 code on a 2018 GMC Sierra?
Repairs may involve replacing the ECM power relay, repairing or replacing damaged wiring, and ensuring all connectors are secure and functioning properly.
Will the check engine light turn off automatically after fixing the P0685 code?
The check engine light may turn off after the issue is resolved, but clearing the code with an OBDII scanner is often necessary.
How much does it cost to fix the P0685 code on a 2018 GMC Sierra?
Repair costs vary but typically range from $50 to $150 for parts (such as a new relay) and additional labor costs depending on the complexity of the issue.
Can a weak battery cause the P0685 code on a 2018 GMC Sierra?
Yes, a weak or failing battery can contribute to insufficient power delivery to the ECM, potentially triggering the P0685 code.
Is replacing the ECM necessary to fix the P0685 code on a 2018 GMC Sierra?
Replacing the ECM is rare and only necessary if all other components, including the relay and wiring, are confirmed to be functioning properly.
Discuss the causes and fixes for P0685 2018 GMC Sierra OBDII Code
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