AutoCodes – Buick – P0688 Buick

P0688 Buick Code - Electronic Control Module Power Relay Sense 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: P0688 Buick indicates Electronic Control Module Power Relay Sense 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 1,172

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 15, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P0688 Buick 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 P0688 Buick - Electronic Control Module Power Relay Sense Circuit/Open - AutoCodes.com — P0688 Buick Code - Electronic Control Module Power Relay Sense Circuit/Open

What does this mean?

What are the Possible Causes of the DTC P0688 Buick?

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 P0688 Buick?

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 Buick 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 P0688 Buick Code

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

- Common symptoms include difficulty starting the vehicle, intermittent stalling, and issues with engine performance.

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

- The code indicates a problem with the Electronic Control Module (ECM) Power Relay Sense Circuit/Open.

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

- 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 cause of OBDII code P0688 in my Buick?

- A thorough inspection of the ECM power relay, circuit wiring, and connectors is recommended. Testing the relay and checking for continuity in the wiring can help pinpoint the issue.

5. Can I drive my Buick with OBDII code P0688?

- It is not recommended to drive the vehicle with this code present, as it can lead to potential stalling and performance issues.

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

- Repair options include replacing the faulty ECM power relay, repairing damaged wiring or connectors, or replacing the ECM if necessary.

7. Will resetting the OBDII code P0688 in my Buick make it go away permanently?

- Resetting the code may temporarily clear it, but if the underlying issue is not addressed, the code is likely to return.

8. Can a DIY enthusiast fix OBDII code P0688 in a Buick?

- Depending on the skill level and access to tools, a DIY enthusiast may be able to address this code by following proper diagnostic procedures and repair steps.

9. Is OBDII code P0688 a common issue in Buick vehicles?

- While not extremely common, occurrences of this code have been reported in Buick vehicles, particularly in older models or those with high mileage.

10. How can I prevent OBDII code P0688 from occurring in my Buick?

- Regular maintenance, checking and replacing the ECM power relay as needed, and ensuring proper wiring connections can help prevent the occurrence of this code.