C1774 Coolant Temperature Out of Range

OBD2 Code: C1774

Description: Coolant temperature out of range.

Definition: This code indicates that the vehicle’s engine control module (ECM) has detected a coolant temperature reading that is outside the expected range. This could be due to a faulty coolant temperature sensor, wiring issues, or problems with the cooling system itself.

C1774 – Coolant Temperature Out of Range

Typical Severity: Moderate

Common Causes

C1774 – Coolant Temperature Out of Range

Common Causes:

• Faulty coolant temperature sensor
• Low coolant level
• Thermostat stuck open or closed
• Wiring issues in the coolant temperature sensor circuit
• Cooling system leaks

 

Common Misdiagnosis

OBD2 Code: C1774

Description: Coolant Temperature Out of Range

Common Misdiagnosis: Replacing the thermostat without checking for a faulty coolant temperature sensor or wiring issues.

 

Common Diagnostic Steps

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OBD2 Code: C1774

Description: Coolant Temperature Out of Range

• Check the coolant level and ensure it is at the proper level.
• Inspect the coolant temperature sensor for damage or corrosion.
• Test the wiring and connectors to the coolant temperature sensor for continuity and any signs of wear or damage.
• Use a scan tool to read live data from the coolant temperature sensor to verify its operation.
• If necessary, replace the faulty coolant temperature sensor.
• Check for any leaks in the cooling system that could affect temperature readings.
• Ensure that there are no air pockets in the cooling system by bleeding it properly.