C1774 – OBD-II DTC

OBD-II DTC C1774 – Coolant Temp Out of Range

DTC C1774 meaning

DTC C1774 refers to a diagnostic trouble code indicating that the coolant temperature is out of the expected range. This code is typically associated with the vehicle’s engine control module (ECM) or powertrain control module (PCM) detecting an abnormal reading from the coolant temperature sensor. The coolant temperature is crucial for optimal engine performance, and deviations from the normal range can lead to various issues.

DTC C1774 symptoms

Common symptoms associated with DTC C1774 may include:

• Engine overheating
• Poor engine performance
• Increased fuel consumption
• Check Engine Light illuminated
• Erratic temperature gauge readings

DTC C1774 causes

Several factors can lead to the triggering of DTC C1774, including:

• Faulty coolant temperature sensor
• Wiring issues or poor connections in the sensor circuit
• Low coolant levels or coolant leaks
• Thermostat malfunction
• Engine overheating due to other mechanical issues

DTC C1774 seriousness

DTC C1774 is considered a serious issue as it can lead to engine overheating and potential engine damage if not addressed promptly. Continuous operation under these conditions can result in severe mechanical failures, which may require costly repairs. It is essential to diagnose and resolve the issue as soon as possible to maintain vehicle reliability and performance.

How to diagnose DTC C1774

To diagnose DTC C1774, follow these steps:

1. Use an OBD-II scanner to confirm the presence of the C1774 code.
2. Inspect the coolant temperature sensor and its wiring for any visible damage or corrosion.
3. Check the coolant level and ensure it is within the recommended range.
4. Test the coolant temperature sensor using a multimeter to verify its resistance values against manufacturer specifications.
5. Examine the thermostat for proper operation and replace if necessary.
6. Clear the code and perform a road test to see if the code reappears.

How to fix DTC C1774 step-by-step instructions

To fix DTC C1774, follow these steps:

1. Identify and replace any faulty coolant temperature sensor.
2. Repair or replace damaged wiring or connectors in the sensor circuit.
3. Top off or replace coolant if levels are low or if there are leaks.
4. Replace the thermostat if it is found to be malfunctioning.
5. After repairs, clear the DTC using an OBD-II scanner.
6. Conduct a test drive to ensure the issue is resolved and the code does not return.

How to erase DTC C1774

To erase DTC C1774, follow these steps:

1. Connect an OBD-II scanner to the vehicle’s diagnostic port.
2. Turn on the ignition without starting the engine.
3. Navigate to the “Erase Codes” or “Clear DTCs” option on the scanner.
4. Confirm the action to clear the trouble codes.
5. Disconnect the scanner and start the engine to verify that the code does not reappear.

Recommended tools for OBD-II diagnostics

Explore our expert picks: The Best OBD2 Scanners for 2025

Easy-to-use Multimeter for reliable diagnostics: AstroAI Auto-ranging Multimeter

Some of the links on this page may be affiliate links, which means we may earn a small commission if you make a purchase. This helps us keep our DTC database up to date and provide valuable content for free. We only recommend products that we have tested and believe to be the best in their class.