Diagnostic Instructions

•	Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

•	Review Strategy Based Diagnosis for an overview of the diagnostic approach.

•	Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0116

Engine Coolant Temperature (ECT) Sensor Performance

Diagnostic Fault Information

Circuit	Short to Ground	High resistance	Open	Short to Voltage	Signal Performance
ECT Sensor Signal	P0117	P0118	P0118	P0118	P0116, P0119, P0128
Low Reference	-	P0118	P0118	P0118	P0119, P0128

Typical Scan Tool Data

ECT Sensor Temperature

Circuit	Short to Ground	Open	Short to Voltage
Operating Conditions: Engine running Parameter Normal Range: -39 to +120°C (-38 to +248°F)
ECT Sensor	143°C (289°F)	-40°C (-40°F)	-40°C (-40°F)
Low Reference	-	-40°C (-40°F)	-40°C (-40°F)

Circuit/System Description

The engine coolant temperature (ECT) sensor is a variable resistor that measures the temperature of the engine coolant. The engine control module (ECM) supplies 5V to the ECT sensor signal circuit and a ground for the low reference circuit.

The purpose of this diagnostic is to determine if the input from the ECT sensor is skewed warmer than normal. The internal clock in the ECM registers how long the engine is OFF. If the time that the engine must be OFF has been fulfilled when starting then the ECM compares the temperature difference between the actual measured ECT with a calibrated ECT model. The information for this model is derived from the previous drive cycle and includes the accumulated mass air flow (MAF), the engine run time, the ambient air temperature and the ECT at the end of the drive cycle.

If the ECM detects that the temperature difference between the measured and modeled ECT is not within an acceptable operating range of each other, then the ECM will continue to run this diagnostic to determine if a block heater was active during the engine OFF time.

Conditions for Running the DTC

•	DTCs P0111, P0112, P0113, P0114, P0117, P0118, P0128, P0502, P0503, P0601, P1621, or P2610 are not set.

•	The vehicle has had a minimum ignition OFF time of 8 hours.

•	The engine is running.

•	The start-up modeled ECT is colder than 50°C (+122°F).

•	The previous accumulated MAF is greater than 6,000 grams.

•	The previous engine run time is greater than 600 seconds. OR

•	The vehicle has had a minimum ignition OFF time of 8 hours.

•	The engine is running.

•	The previous ECT at engine shutdown is warmer than 75°C (+167°F).

•	The previous accumulated MAF is greater than 6,000 grams.

•	The previous engine run time is greater than 600 seconds.

•	This DTC runs once per ignition cycle within the enabling conditions.

Conditions for Setting the DTC

P0116

The ECM detects a temperature difference at initial power-up that indicates that the actual measured ECT is 10°C (18°F) greater than the modeled ECT, and an active block heater has not been detected.

Action Taken When the DTC Sets

DTC P0116 is a Type B DTC.

Conditions for Clearing the MIL/DTC

DTC P0116 is a Type B DTC.

Diagnostic Aids

•	Engine coolant that is leaking through the sensor will create a high resistance short to ground. This condition results in less voltage on the ECT sensor signal circuit, which is interpreted by the ECM as a warmer ECT.

•	The ECM memory which includes the ignition OFF timer is maintained by battery power. If the ECM or the battery are disconnected for less than 15 seconds the proper operation of the ECM memory and the timer can be disrupted. Always disconnect these components for greater than 30 seconds.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

•	Circuit Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1.	Turn OFF the ignition.

2.	Inspect the cooling system surge tank for the proper engine coolant level. Refer to Cooling System Leak Testing and Cooling System Draining and Filling (LAU/A28NER) Cooling System Draining and Filling (LBS/A20DTH) Cooling System Draining and Filling (LHU/A20NFT).

3.

If the ignition has been OFF for 8 hours or greater, the intake air temperature (IAT) sensor, the IAT sensor 2, and the ECT sensor should be within 9°C (16°F) of each other and also the ambient temperature. Ignition ON, observe the scan tool IAT Sensor, IAT Sensor 2 and the ECT Sensor parameters. Compare those sensor parameters to each other and also to the ambient temperature to determine if the ECT sensor is skewed warmer.

4.	Engine running, observe the ECT Sensor parameter. The reading should be between -39 to +120°C (-38 to +248°F) depending on the current ambient temperature and the vehicle operating conditions.

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.

Circuit/System Testing

1.	Ignition OFF for 90 seconds, disconnect the harness connector at the B34 ECT sensor.

2.	Inspect the ECT sensor terminals for corrosion and for engine coolant leaking through the sensor.

3.	Test for less than 5 Ω between the low reference circuit terminal A and ground.

4.	If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K20 ECM.

5.	Ignition ON, verify the scan tool ECT Sensor parameter is colder than -39°C (-38°F).

6.	If warmer than the specified range, test the signal circuit terminal B for a short to ground. If the circuit tests normal, replace the K20 ECM.

7.	Install a 3A fused jumper wire between the signal circuit terminal B and the low reference circuit terminal A. Verify the scan tool ECT Sensor parameter is warmer than 142°C (288°F).

8.	If colder than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 ECM.

9.	If the circuits test normal, test or replace the B34 ECT sensor.

Component Testing

Measure and record the resistance of the ECT sensor at various ambient temperatures, then compare those measurements to the Temperature Versus Resistance (IAT 2) Temperature Versus Resistance (ECT) Temperature Versus Resistance (IAT) table.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

•	Engine Coolant Temperature Sensor Replacement

•	Control Module References for ECM replacement, setup, and programming