AutoCodes – GMC – P0691 GMC

P0691 GMC Code - Cooling Fan 1 Control Circuit Low

Quick Answer

The engine cooling fan system is composed of electric cooling fan and a cooling fan control module. Common causes include Faulty Cooling Fan 1 Relay, Cooling Fan 1 Relay harness is open or shorted, Cooling Fan 1 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: P0691 GMC indicates Cooling Fan 1 Control Circuit Low.
Common causes: Common causes include Faulty Cooling Fan 1 Relay, Cooling Fan 1 Relay harness is open or shorted, Cooling Fan 1 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 2,934

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 Jul 19, 2022

Description
Possible Causes
How To Fix
Cost to Diagnose
FAQs
Comments
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Code P0691 GMC Description

The engine cooling fan system is composed of electric cooling fan and a cooling fan control module. The Engine Control Module (ECM) controls the fan speed by sending a Pulse Width Modulated (PWM) signal to the cooling fan control module. The cooling fan control module varies the voltage drop across the cooling fan motor in relation to the pulse width modulated signal, allowing the cooling fan to operate at variable speeds. The cooling fan speed is affected by many different operating conditions and the ECM will adjust the duty cycle based on cooling system requirements.
Generally, the ECM will operate the cooling fan at specific percentages but, may scale the percentages either higher or lower in response to generator demand. The percentages at which the cooling fan operates may vary between vehicle lines and engines.
The cooling fan control module is thermally protected to prevent module damage in the case of a short circuit condition in the cooling fan motor. The scan tool output control is only capable of operating the cooling fan in the speed percentages allowed by the ECM. When multiple cooling fan speed requests are received, the ECM operates the fan at the highest of the speed requests.
The Diagnostic Trouble Code (DTC) will be set when the commanded state of the driver and the actual state of the control circuit do not match for greater than 5 s.

**Cooling Fan design may vary

OBDII Code P0691 GMC - Cooling Fan 1 Control Circuit Low - AutoCodes.com — P0691 GMC Code - Cooling Fan 1 Control Circuit Low

What does this mean?

What are the Possible Causes of the DTC P0691 GMC?

Faulty Cooling Fan 1 Relay
Cooling Fan 1 Relay harness is open or shorted
Cooling Fan 1 Relay circuit poor electrical connection
Faulty Cooling Fan 1
Faulty Cooling Fan Control Module
Faulty Engine Control Module (ECM)

How to Fix the DTC P0691 GMC?

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 P0691 GMC 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 P0691 GMC code?

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Need Help with the Code?

Get the P0691 GMC code diagnosed by a professional: Find a repair shop in your area

Information for Specific GMC Models

P0691 2014 GMC Sierra — Cooling Fan Speed Output Circuit Low Voltage
P0691 2015 GMC Sierra — Cooling Fan Speed Output Circuit Low Voltage
P0691 2016 GMC Sierra — Cooling Fan Speed Output Circuit Low Voltage
P0691 2017 GMC Sierra — Cooling Fan Speed Output Circuit Low Voltage
P0691 2018 GMC Sierra — Cooling Fan Speed Output Circuit Low Voltage

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 P0691 GMC Code

1. What are the common symptoms of OBDII code P0691 in a GMC related to the Cooling Fan 1 Control Circuit Low?

- Common symptoms may include the cooling fan not running at the correct speed or not turning on at all, engine overheating, and an illuminated check engine light.

2. What are the possible causes of the Cooling Fan 1 Control Circuit Low OBDII code in a GMC?

- Possible causes include a faulty cooling fan motor, a malfunctioning cooling fan relay, damaged wiring or connectors in the cooling fan circuit, or a problem with the engine control module (ECM).

3. How can I diagnose the Cooling Fan 1 Control Circuit Low issue in my GMC?

- Diagnosis typically involves checking the cooling fan operation, inspecting the cooling fan relay, testing the wiring and connectors for damage, and using a scan tool to retrieve and analyze the OBDII code data.

4. What are some repair tips for addressing OBDII code P0691 in a GMC?

- Repair tips may include replacing the cooling fan motor if it's faulty, replacing the cooling fan relay if needed, repairing any damaged wiring or connectors, and resetting the ECM after completing the repairs.

5. Can driving with the OBDII code P0691 related to the Cooling Fan 1 Control Circuit Low cause further damage to my GMC?

- Continuing to drive with this issue can lead to engine overheating and potential engine damage, so it's important to address the problem promptly to prevent any further issues.

6. Is it safe to clear the OBDII code P0691 related to the Cooling Fan 1 Control Circuit Low without fixing the underlying problem?

- Clearing the code without fixing the underlying issue may temporarily turn off the check engine light, but the problem will likely persist and could lead to engine overheating if not properly addressed.

7. How much does it typically cost to repair OBDII code P0691 in a GMC related to the Cooling Fan 1 Control Circuit Low?

- The cost of repairs can vary depending on the specific cause of the issue, but it may involve replacing the cooling fan motor, relay, or addressing any wiring issues. Costs can range from a few hundred to over a thousand dollars.

8. Are there any preventative measures I can take to avoid OBDII code P0691 in my GMC?

- Regularly inspecting the cooling fan system, performing routine maintenance checks, and addressing any cooling system issues promptly can help prevent the occurrence of the Cooling Fan 1 Control Circuit Low code.

9. Can a DIY enthusiast with some automotive knowledge repair OBDII code P0691 in a GMC themselves?

- Depending on the cause of the issue, DIY repairs may be possible for those with automotive knowledge and the necessary tools. However, complex issues or wiring problems may require professional assistance.

10. How long does it typically take to repair OBDII code P0691 in a GMC related to the Cooling Fan 1 Control Circuit Low?

- Repair times can vary based on the specific cause of the issue, but it may take a few hours to a full day to diagnose, repair, and test the cooling fan system to resolve the problem.