AutoCodes – Generic – P2681

P2681 Code - Engine Coolant Bypass Valve Control Circuit/Open

Quick Answer

The passenger compartment heater coolant control valve regulates the engine coolant flow into the cabin heater loop depending on engine coolant temperature and ambient temperature conditions. Common causes include Faulty Engine Coolant Bypass Valve, Engine Coolant Bypass Valve harness is open or shorted, Engine Coolant Bypass Valve 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: P2681 indicates Engine Coolant Bypass Valve Control Circuit/Open.
Common causes: Common causes include Faulty Engine Coolant Bypass Valve, Engine Coolant Bypass Valve harness is open or shorted, Engine Coolant Bypass Valve 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 61,473

How popular is this code, among other codes? Medium

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 Jan 03, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P2681 Description

The passenger compartment heater coolant control valve regulates the engine coolant flow into the cabin heater loop depending on engine coolant temperature and ambient temperature conditions. The passenger compartment heater coolant control valve has two positions: ByPass or Link. In the ByPass position, the coolant in the engine loop and heater loop are separated and in the link position the coolant circulates through both loops. The valve movement is controlled by a PWM signal. A 50% duty cycle is a normal duty cycle. A 75% duty cycle represents a valve commanded to the link position. A 25% duty cycle represents a valve commanded to the ByPass position. The passenger compartment heater coolant control valve uses an internal position sensor that sends a signal to the hybrid powertrain control module to determine the valve position.
When the engine coolant temperature heats up, a valve learn procedure takes place. The hybrid powertrain control module 2 commands the valve to the link position and records the voltage coming back from the position sensor. Then the hybrid powertrain control module 2 commands the valve back to the bypass position and records the voltage coming back from the position sensor. The voltage values in both the link and bypass positions must fall within calibrated ranges.

OBDII Code P2681 - Engine Coolant Bypass Valve Control Circuit/Open - AutoCodes.com — P2681 Code - Engine Coolant Bypass Valve Control Circuit/Open

What does this mean?

What are the Possible Causes of the DTC P2681?

Faulty Engine Coolant Bypass Valve
Engine Coolant Bypass Valve harness is open or shorted
Engine Coolant Bypass Valve circuit poor electrical connection

How to Fix the DTC P2681?

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 P2681 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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Need more information on how to fix the P2681 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the P2681 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

P2681 Buick — Engine Coolant Bypass Valve Control Circuit/Open
P2681 Cadillac — Engine Coolant Bypass Valve Control Circuit/Open
P2681 Chevrolet — Engine Coolant Bypass Valve Control Circuit/Open
P2681 Ford — Engine Coolant Bypass Valve 'A' Control Circuit/Open
P2681 GMC — Engine Coolant Bypass Valve Control Circuit/Open
P2681:15 Lexus — Engine Coolant Bypass Valve Circuit Short to Battery or Open
P2681:11 Lexus — Engine Coolant Bypass Valve Circuit Short to Ground
P2681 Lincoln — Engine Coolant Bypass Valve 'A' Control Circuit/Open
P2681 Mercury — Engine Coolant Bypass Valve 'A' Control Circuit/Open
P2681:15 Toyota — Engine Coolant Bypass Valve Circuit Short to Battery or Open
P2681:11 Toyota — Engine Coolant Bypass Valve Circuit Short to Ground

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 P2681 Code

1. What are the common symptoms of OBDII code P2681?

The common symptoms of OBDII code P2681 include engine overheating, poor heater performance, and a check engine light illuminated on the dashboard.

2. What can cause the Engine Coolant Bypass Valve Control Circuit/Open code P2681?

The P2681 code is typically caused by a faulty engine coolant bypass valve, damaged wiring or connectors in the coolant bypass valve circuit, or a malfunctioning engine control module (ECM).

3. How serious is the P2681 code related to the Engine Coolant Bypass Valve Control Circuit/Open?

The P2681 code is moderately serious as it can lead to engine overheating and potential damage if not addressed promptly. It is recommended to address this issue as soon as possible to prevent further issues.

4. Can I drive my vehicle with the P2681 code present?

It is not recommended to drive your vehicle with the P2681 code present, especially if you are experiencing symptoms like engine overheating. Continuing to drive may cause further damage to the engine.

5. How can I diagnose and repair the P2681 code on my own?

Diagnosing and repairing the P2681 code usually involves checking the coolant bypass valve for proper operation, inspecting the wiring and connectors for any damage, and testing the ECM for faults. It is advisable to have a professional mechanic perform these diagnostics.

6. Will resetting the check engine light make the P2681 code go away?

Resetting the check engine light may temporarily clear the code, but it will likely return if the underlying issue causing the P2681 code is not addressed.

7. Can a faulty thermostat cause the P2681 code to appear?

While a faulty thermostat is not a direct cause of the P2681 code, it can contribute to engine overheating issues that may trigger this code. It is essential to address all potential cooling system problems when dealing with OBDII code P2681.

8. How much does it typically cost to repair the P2681 code?

The cost of repairing the P2681 code can vary depending on the cause of the issue, parts needed, and labor costs. It is recommended to get a diagnostic from a qualified mechanic to determine the exact cost of repair.

9. Are there any preventive measures to avoid the P2681 code in the future?

Regular maintenance of the cooling system, including checking coolant levels, replacing coolant as recommended, and inspecting the bypass valve and related components, can help prevent issues that may lead to the P2681 code.

10. Can a DIY enthusiast with basic automotive knowledge fix the P2681 code?

While some DIY enthusiasts may be able to address simple cooling system issues, diagnosing and repairing the P2681 code may require specialized tools and expertise. It is advisable to consult with a professional mechanic for proper diagnosis and repair.