P112F CHEVROLET – Radiator Coolant Temperature Sensor

Code P112F Chevrolet: Possible Causes

• Faulty Radiator Coolant Temperature (RCT) Sensor: Internal resistance out of specification or electronic failure.

• Electrical Harness Problem: Open circuit, short circuit, or damaged wires between the RCT sensor and the ECM.

• Faulty Connections: Oxidation, corrosion, or improperly engaged pins in the sensor or ECM connector.

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Common Symptoms

• 🔥 Check Engine Light illuminated (or “Service Engine Soon” message).

• Engine overheating or abnormal temperature displayed on the dashboard.

• Unstable idle or loss of power when cold.

• Increased fuel consumption (due to a non-optimized air-fuel mixture).

• Risk of limp mode activation to protect the engine.

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Meaning of Code P112F
The RCT (Radiator Coolant Temperature) sensor measures the coolant temperature at the radiator level. Unlike the ECT (Engine Coolant Temperature) sensor, which monitors the engine temperature, the RCT evaluates the cooling efficiency after passing through the radiator.

• Operation:

  • The RCT sensor is a thermistor (a variable resistor with temperature).

  • The ECM sends a 5 V voltage to the sensor circuit and uses the return voltage to calculate the temperature.

  • In case of prolonged engine shutdown, the ECM compares the RCT data with the ECT data to detect anomalies (e.g., abnormal temperature difference).

Code P112F is triggered when:

• The temperature measured by the RCT is inconsistent with that of the ECT after a specific shutdown period.

• The RCT signal falls outside the tolerance ranges specified by the manufacturer.

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Diagnostic and Repair Procedure

1. Visual Inspection

   • Inspect the RCT sensor harness: Check for cut, pinched, or heat-exposed wires.

   • Check the connectors: Clean the pins with contact cleaner and ensure they are intact and securely fastened.

2. RCT Sensor Test

   • Resistance Measurement:

     • Disconnect the sensor and use a multimeter in ohmmeter mode.

     • Compare the resistance with reference values (e.g., ~2,500 Ω at 20°C, ~300 Ω at 80°C).

   • Voltage Measurement:

     • Reconnect the sensor and measure the voltage between the signal wire and engine ground (should vary between 0.5 V and 4.5 V depending on temperature).

3. Checking Power and Ground

   • Ensure the sensor receives 5 V on the reference wire and that the ground is stable (resistance < 0.5 Ω between the ground pin and the battery).

4. Comparison with the ECT Sensor

   • Use a diagnostic tool to read live data from the RCT and ECT sensors.

   • After an engine shutdown period (e.g., 1 hour), verify that the temperature difference between the two sensors is consistent (generally < 10°C).

5. Replacement or Repair

   • If the RCT sensor is faulty, replace it with an ACDelco part (recommended for Chevrolet).

   • Repair the damaged harness using waterproof connectors to prevent moisture ingress.

6. Reset and Final Test

   • Clear the P112F code with an OBD2 tool.

   • Perform a complete drive cycle (engine heating and cooling) to confirm the fault is resolved.

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Important Tip
If the code persists after replacing the sensor:

• Check the thermostat or water pump: A coolant circulation fault can distort the measurements.

• Check the coolant level and quality (an improper mixture can affect thermal conductivity).

Note: A faulty RCT sensor can lead to engine overheating or premature wear of seals. Do not ignore this code!