AutoCodes – Buick – P0691 Buick

P0691 Buick 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 Buick 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 1,231

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

What does this mean?

What are the Possible Causes of the DTC P0691 Buick?

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 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 P0691 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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Need Help with the Code?

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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 P0691 Buick Code

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

- Common symptoms include the cooling fan not working properly, engine overheating, and illuminated engine warning light.

2. What are the possible causes of OBDII code P0691 in a Buick indicating Cooling Fan 1 Control Circuit Low?

- Possible causes include a faulty cooling fan relay, damaged wiring or connectors in the cooling fan circuit, or a malfunctioning cooling fan control module.

3. How can I diagnose the issue causing OBDII code P0691 in my Buick related to Cooling Fan 1 Control Circuit Low?

- You can diagnose the issue by checking the cooling fan fuse, inspecting the wiring and connectors in the cooling fan circuit, testing the cooling fan relay, and checking the cooling fan control module.

4. Can a malfunctioning coolant temperature sensor cause OBDII code P0691 in a Buick for Cooling Fan 1 Control Circuit Low?

- Yes, a faulty coolant temperature sensor can sometimes trigger this code by providing incorrect temperature readings to the cooling fan control system.

5. What are some repair tips for resolving OBDII code P0691 in a Buick associated with Cooling Fan 1 Control Circuit Low?

- Repair tips include checking and replacing the cooling fan relay, repairing any damaged wiring or connectors, testing and replacing the cooling fan control module if necessary, and ensuring the cooling system is functioning properly.

6. Is it safe to continue driving my Buick with OBDII code P0691 related to Cooling Fan 1 Control Circuit Low?

- It is not recommended to drive your Buick with this code active, as it can lead to engine overheating and potential damage. It's best to address the issue promptly.

7. Can resetting the OBDII system clear the P0691 code in a Buick indicating Cooling Fan 1 Control Circuit Low?

- Resetting the OBDII system may temporarily clear the code, but if the underlying issue causing the code is not addressed, it is likely to reappear.

8. Will a mechanic be able to determine the exact cause of OBDII code P0691 in my Buick for Cooling Fan 1 Control Circuit Low?

- A qualified mechanic can perform diagnostic tests to pinpoint the exact cause of the code, such as testing components in the cooling fan circuit and using specialized equipment.

9. Are there any recalls or technical service bulletins related to OBDII code P0691 in Buick vehicles for Cooling Fan 1 Control Circuit Low?

- It's advisable to check with your Buick dealership or visit the National Highway Traffic Safety Administration's website for any relevant recalls or technical service bulletins related to this code.

10. How much can I expect to pay to repair OBDII code P0691 in a Buick associated with Cooling Fan 1 Control Circuit Low?

- The cost of repair can vary depending on the exact cause of the issue, but it may involve expenses for parts replacement, labor costs, and diagnostic fees. Be sure to obtain estimates from reputable repair shops.