AutoCodes – Mercury – P0688 Mercury

P0688 Mercury Code - Electronic Control Module Power Relay Sense 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: P0688 Mercury indicates Electronic Control Module Power Relay Sense 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 1,393

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
Cost to Diagnose
FAQs
Comments
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Code P0688 Mercury 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 P0688 Mercury - Electronic Control Module Power Relay Sense Circuit/Open - AutoCodes.com — P0688 Mercury Code - Electronic Control Module Power Relay Sense Circuit/Open

What does this mean?

What are the Possible Causes of the DTC P0688 Mercury?

Faulty Engine Control Module (ECM) power relay
ECM power relay harness is open or shorted
ECM power relay circuit poor electrical connection
Faulty ECM

How to Fix the DTC P0688 Mercury?

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 is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0688 Mercury 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 P0688 Mercury code?

Need more information on how to fix the P0688 Mercury code? Get Access to Factory Service Manuals

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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 P0688 Mercury Code

1. What are the common symptoms of OBDII code P0688 in a Mercury vehicle?

- Common symptoms include engine stalling, difficulty starting the vehicle, and illuminated check engine light.

2. What does the OBDII code P0688 in a Mercury indicate?

- The code P0688 indicates a problem with the Electronic Control Module (ECM) power relay sense circuit being open.

3. What are the possible causes of OBDII code P0688 in a Mercury?

- Possible causes include a faulty ECM power relay, damaged wiring or connectors in the power relay circuit, or a malfunctioning ECM.

4. How can I diagnose the OBDII code P0688 in my Mercury?

- Diagnosis involves checking the ECM power relay and related wiring for continuity, inspecting for any loose or damaged connections, and testing the ECM for proper functioning.

5. Can I still drive my Mercury with the OBDII code P0688?

- It is not recommended to drive the vehicle with code P0688 as it can lead to potential engine performance issues and further damage if left unresolved.

6. How can I repair OBDII code P0688 in my Mercury?

- Repair involves replacing the faulty ECM power relay if necessary, repairing any damaged wiring or connectors, and clearing the trouble codes from the vehicle's system.

7. Is it possible to reset the OBDII code P0688 in my Mercury without fixing the underlying issue?

- While you can clear the trouble code temporarily, it will likely reappear until the root cause of the problem is addressed.

8. How much does it typically cost to repair OBDII code P0688 in a Mercury?

- The cost of repair can vary depending on the specific issue, but it may range from $100 to $300 for parts and labor.

9. Will OBDII code P0688 cause my Mercury to fail an emissions test?

- Yes, having an unresolved OBDII code like P0688 can cause your Mercury to fail an emissions test due to potential issues with engine performance.

10. Can I fix OBDII code P0688 in my Mercury myself, or do I need to take it to a mechanic?

- While some DIY enthusiasts may be able to address the issue, it is recommended to seek assistance from a qualified mechanic for proper diagnosis and repair to ensure the problem is resolved correctly.