P2181
DTC P2181
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptor
DTC P2181
- Engine Cooling System Performance
Circuit/System Description
The engine control module (ECM) monitors temperature difference between the engine coolant temperature (ECT) sensor and the radiator coolant temperature (RCT) sensor during a cold start-up. The purpose of this diagnostic is to analyze the engine coolant thermostat for being stuck open.
Conditions for Running the DTC
* DTCs P00B3, P00B4, P00B6, P0101, P0102, P0103, P0111, P0112, P0113, P0114, P0116, P0117, or P0118 are not set.
* The engine run time is between 70 s and 30 min.
* The engine coolant temperature (ECT) sensor at start-up is between -10°C to +59°C (14°F to 138°F).
* The intake air temperature (IAT) sensor is between -7°C to +60°C (-4°F to +140°F).
* The airflow into the engine is between 1 to 100 g/s.
* The DTC runs once per ignition cycle when the above conditions are met.
Conditions for Setting the DTC
The ECM detects the engine coolant thermostat is stuck open for at least 2.5 min.
Action Taken When the DTC Sets
DTC P2181 is a Type B DTC
Conditions for Clearing the DTC
DTC P2181 is a Type B DTC
Diagnostic Aids
* Insufficient vehicle interior heating is an indication of improper thermostat operation.
* The scan tool Desired ECT Sensor and the ECT Sensor parameters should be within 5°C (9°F) when the engine is at operating temperature.
* A resistance condition in the ECT sensor circuits may cause this DTC. This condition results in a greater voltage on the ECT sensor signal circuit, which is interpreted by the ECM as a colder ECT.
Reference Information
Schematic Reference
Engine Controls Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
Description and Operation
* Cooling System Description and Operation Cooling System
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
1. Engine running, observe the DTC information with a scan tool. DTC P00B3, P00B4, P00B6, P0117, or P0118 should not be set.
• If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.
2. Verify the coolant in the radiator surge tank is at the correct level and there are no engine coolant leaks. Refer to Cooling System Draining and Filling Cooling System Draining and Filling and Loss of Coolant Loss of Coolant.
Note: Depending on ambient temperature, it may take up to 4 min for the temperature to increase greater than the specified value.
3. Engine idling for 15 min with the A/C OFF. Verify the engine cooling fan is not ON at all times.
4. Command the Engine Coolant Thermostat Heater to 0 % with a scan tool. Increase the engine speed to 3,000 RPM. Observe the scan tool ECT sensor parameter. The temperature should increase to greater than 102°C (215°F).
• If less than the specified value, replace the E41 engine coolant thermostat heater.
5. Operate the vehicle within the conditions for running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the freeze frame/failure records data.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.
Engine Coolant Thermostat Replacement (LUV) Service and RepairEngine Coolant Thermostat Replacement (LUW) Service and Repair