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, P0101, P0102, P0103, P0112, P0113, or P0114 are not set.
* The engine run time is between 70 s and 22 m.
* The engine coolant temperature (ECT) sensor at start-up is between -20°C to +75°C (19 to 140°F).
* The intake air temperature (IAT) sensor is between -7°C to +75°C (-4°F to +167°F).
* The airflow into the engine is between 11 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 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 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 ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector End Views By Name)
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 (Programming and Relearning) 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, or P0481 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 (Vac N Fill) (Cooling System Draining and Filling (Vac N Fill)) Cooling System Draining and Filling (Static Fill LGH) (Cooling System Draining and Filling (Static Fill VIN L)) 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. Increase the engine speed to 3000 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 Engine Coolant Thermostat.

4. 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 (V6) (Service and Repair) Engine Coolant Thermostat Replacement (LLY,LBZ) (Service and Repair) Engine Coolant Thermostat Replacement (LGH) (Service and Repair)