P0691 2018 GMC Sierra Code - Cooling Fan Speed Output Circuit Low Voltage
Quick Answer
The diagnostic trouble code P0691 for a 2018 GMC Sierra indicates a problem with the Cooling Fan Speed Output Circuit Low Voltage. Common causes include Faulty cooling fan relay: A defective cooling fan relay can disrupt the voltage signal to the cooling fan speed output circuit, causing it to operate at low voltage, Wiring issues: Damaged or corroded wiring connections can also lead to a low voltage signal in the cooling fan speed output circuit, Blown fuse: If the fuse that controls the cooling fan circuit is blown, it can result in low voltage to the cooling fan speed output circuit. 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 2018 GMC Sierra indicates Cooling Fan Speed Output Circuit Low Voltage.
- Common causes
- Common causes include Faulty cooling fan relay: A defective cooling fan relay can disrupt the voltage signal to the cooling fan speed output circuit, causing it to operate at low voltage, Wiring issues: Damaged or corroded wiring connections can also lead to a low voltage signal in the cooling fan speed output circuit, Blown fuse: If the fuse that controls the cooling fan circuit is blown, it can result in low voltage to the cooling fan speed output circuit.
- 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 P0691 2018 GMC Sierra Description
The diagnostic trouble code P0691 for a 2018 GMC Sierra indicates a problem with the Cooling Fan Speed Output Circuit Low Voltage. This code is set when the Engine Control Module (ECM) detects that the voltage signal from the cooling fan speed output circuit is below the specified range. The cooling fan is a crucial component in the vehicle's cooling system, responsible for regulating the engine temperature by dissipating heat. When the cooling fan speed output circuit is not functioning properly, it can lead to inadequate cooling system performance, potentially causing the engine to overheat.
Common Causes of P0691 2018 GMC Sierra
- Faulty cooling fan relay: A defective cooling fan relay can disrupt the voltage signal to the cooling fan speed output circuit, causing it to operate at low voltage.
- Wiring issues: Damaged or corroded wiring connections can also lead to a low voltage signal in the cooling fan speed output circuit.
- Blown fuse: If the fuse that controls the cooling fan circuit is blown, it can result in low voltage to the cooling fan speed output circuit.
- Faulty cooling fan motor: A malfunctioning cooling fan motor may not be able to operate at the correct speed, resulting in low voltage in the cooling fan speed output circuit.
- ECM failure: In rare cases, a failure of the Engine Control Module (ECM) could also trigger this code, as it is responsible for monitoring and controlling the cooling fan speed output circuit.
Symptoms of P0691 2018 GMC Sierra
- Engine overheating: One of the most common symptoms of a faulty cooling fan speed output circuit is engine overheating. If the cooling fan is not operating at the correct speed, it may not be able to sufficiently cool the engine, leading to overheating.
- High engine temperature gauge: A high engine temperature gauge reading may indicate that the engine is running hotter than normal, which could be a result of inadequate cooling due to a faulty cooling fan speed output circuit.
- Poor air conditioning performance: If the cooling fan is not functioning properly, it can also impact the air conditioning system's performance, as the cooling fan helps cool the condenser when the AC is running.
- Engine stalling: In severe cases, a malfunctioning cooling fan speed output circuit can lead to engine stalling, as overheating can cause the engine to shut down to prevent damage.
How to Fix P0691 2018 GMC Sierra
- Diagnose the issue: Begin by using a scan tool to retrieve the trouble code and assess the cooling fan speed output circuit for any faults. Check the cooling fan relay, wiring connections, fuse, and cooling fan motor for any issues.
- Replace faulty components: If a specific component such as the cooling fan relay, wiring, fuse, or cooling fan motor is found to be faulty, it should be replaced with a new part.
- Repair wiring connections: If the issue is related to damaged or corroded wiring connections, repair or replace the affected wires to ensure proper voltage flow in the cooling fan speed output circuit.
- Clear trouble codes: Once the repairs are completed, clear the trouble codes from the ECM memory using a scan tool to reset the system and ensure the issue has been resolved.
- Test the cooling system: After completing the repairs, test the cooling system to ensure that the cooling fan is operating at the correct speed and that the voltage in the cooling fan speed output circuit is within the specified range.
Cost to Fix P0691 2018 GMC Sierra
The typical repair costs for addressing a P0691 code related to the Cooling Fan Speed Output Circuit Low Voltage can vary depending on the specific cause of the issue. In general, the cost of replacing components like the cooling fan relay, wiring, fuse, or cooling fan motor can range from $100 to $500, including parts and labor. However, the actual cost may be higher or lower based on the extent of the repairs needed and the rates charged by auto repair shops. It is recommended to consult with a qualified mechanic or service center to obtain a more accurate estimate based on the specific circumstances of the vehicle in question. Labor rates at auto repair shops typically range from $80 to $150 per hour, but can vary based on location and other factors.
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Frequently Asked Questions about P0691 2018 GMC Sierra Code
1. What does the OBDII code P0691 mean on a 2018 GMC Sierra?
P0691 indicates a low voltage issue in the cooling fan speed output circuit, which controls the fan's operation to prevent the engine from overheating.
2. What are the common symptoms of the P0691 code in a 2018 GMC Sierra?
Symptoms can include the engine running hotter than normal, the cooling fan not operating, or the Check Engine Light illuminating.
3. What causes the P0691 code to appear in a 2018 GMC Sierra?
Common causes include a faulty cooling fan relay, a damaged cooling fan motor, wiring issues such as shorts or open circuits, or a malfunctioning Engine Control Module (ECM).
4. How do I troubleshoot the P0691 code on my 2018 GMC Sierra?
Start by inspecting the cooling fan relay, fan motor, and related wiring for damage or loose connections. Use a multimeter to check for proper voltage and continuity in the circuit.
5. Can I drive my 2018 GMC Sierra with the P0691 code active?
It’s not recommended, as the cooling fan may not function properly, potentially leading to engine overheating and significant damage.
6. How is the P0691 code typically fixed on a 2018 GMC Sierra?
Repairs may include replacing a faulty cooling fan relay, repairing or replacing damaged wiring, replacing a defective fan motor, or reprogramming or replacing the ECM if necessary.
7. How much does it cost to fix the P0691 code on a 2018 GMC Sierra?
Repair costs can vary but generally range from $100 to $500, depending on whether the issue is with the relay, wiring, fan motor, or ECM.
8. Can a blown fuse cause the P0691 code in a 2018 GMC Sierra?
Yes, a blown fuse in the cooling fan circuit can result in low voltage and trigger the P0691 code.
9. How can I prevent the P0691 code from recurring in my 2018 GMC Sierra?
Regular maintenance, including checking the cooling fan system and associated wiring for wear or damage, can help prevent this issue.
10. Will clearing the P0691 code with a scan tool fix the issue in a 2018 GMC Sierra?
Clearing the code may turn off the Check Engine Light temporarily, but the underlying issue must be repaired to prevent the code from returning.
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