P2181

DTC P2181 (LUW)

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) controls the pulse width modulated (PWM) engine coolant thermostat heater. The thermostat controls coolant flow and regulates the engine operating temperature. Ignition voltage is supplied directly to the engine coolant thermostat heater. The ECM controls the engine coolant thermostat heater by grounding the control circuit with a solid state device called a driver.

Conditions for Running the DTC

* DTCs P00B3, P00B4, P0101, P0102, P0103, P0112, P0113, or P0114 are not set.
* The engine run time is between 2-22 min.
* The engine coolant temperature (ECT) sensor at start-up is between -20 to +45°C (19-113°F).
* The intake air temperature (IAT) sensor is between -7 to +60°C (-4 to +140°F).
* The engine coolant thermostat heater command is greater than 50%.
* The airflow into the engine is between 11-100 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 heated thermostat is stuck open for 160 s.

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.
* The engine coolant thermostat heater has a mechanical fail-safe in case of an electrical condition with the thermostat heater. The mechanical thermostat will open at approximately 104°C (220°F). The mechanical thermostat will cycle from approximately 104°C (220°F) to approximately 98°C (208°F).

Reference Information
Schematic Reference

Engine Controls Schematics (LUW) [1][2]Electrical Diagrams
Connector End View Reference

Component Connector End Views Sunshade - Left (D6I)
Description and Operation

Cooling System Description and Operation (LDE, LLU, LXV, 2H0 LUW and LFH) Description and OperationCooling System Description and Operation (1.4L LUH, LUJ, and LUV) Description and Operation
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. Ignition ON, observe the DTC information with a scan tool. DTC P00B3, P00B4, P00B6, P0117, P0118, P0480, P0481, P0597, P0598, or P0599 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 (Static Fill) Cooling System Draining and Filling (Static Fill)Cooling System Draining and Filling (GE-47716 Fill) Cooling System Draining and Filling (GE-47716 Fill) and Loss of Coolant Loss of Coolant.
3. Engine idling for 15 min with the A/C OFF. Verify the engine cooing fan is not ON at all times. Refer to PSD SIE TITLE Error: SIE linked to empty Cell ID 37447.

Note: Depending on ambient temperature, it may take up to 4 min for the temperature to increase greater than the specified value.

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