DTC P0117 Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage. GMC Truck Sonoma Pickup

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2000 🢒 Sonoma Pickup - 2WD 🢒 DTC 🢒 DTC P0117 Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage

Engine Controls Components
MAP, IAT, TPS, and ECT Sensors
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The engine coolant temperature (ECT) sensor is a thermistor which controls the signal voltage to the powertrain control module (PCM). The PCM supplies a 5 volt reference and a ground to the ECT sensor. Whenever the engine is cold, the ECT sensor resistance will be high.

As the engine warms up, the ECT sensor resistance decreases and the voltage drops. At the normal engine operating temperature, the voltage will be between 1.5 and 2.0 volts.

The engine coolant temperature sensor is one of the inputs used to control the following items:

•	The fuel delivery

•	The torque converter clutch (TCC)

•	The ignition control (IC)

•	The evaporative emission (EVAP) canister purge valve

•	The idle air control (IAC) valve

Conditions For Running The DTC

The engine run time is more than 128 seconds.

Conditions for Setting the DTC

The ECT sensor indicates that the engine coolant temperature is more than 138°C (280°F) for 6.25 seconds.

Action Taken When the DTC Sets

•	The malfunction indicator lamp (MIL) illuminates after 2 consecutive ignition cycles with the malfunction present.

•	The PCM records the operating conditions at the time the diagnostic fails. The Freeze Frame and Failure Records buffers stores this information.

•	A history DTC is stored.

•	The PCM defaults to 20°C (68°F) for the first 60 seconds of engine run time. After 60 seconds the ECT will default to 92°C (198°F) for engine coolant temperature. The scan tool will not show the defaulted value.

Conditions for Clearing the MIL/DTC

•	The MIL will turn OFF after 3 consecutive ignition cycles in which the diagnostic runs without a fault.

•	A history DTC will clear after 40 consecutive warm up cycles without a fault.

•	A scan tool can clear the DTCs.

Diagnostic Aids

After starting the engine, the temperature should rise steadily to about 90°C (194°F) then stabilize when the thermostat opens.

Check for an intermittent short to ground in the ECT sensor signal circuit by moving the PCM harness at various locations while monitoring the ECT voltage on the scan tool. If the voltage varies, look for a short to ground in the area of the harness that caused the variance. For more information about intermittence Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Use the Temperature vs. Resistance value table to test the coolant sensor at various temperature levels in order to evaluate the possibility of a skewed (mis-scaled) sensor. A skewed sensor could affect vehicle driveability. Refer to Temperature Versus Resistance .

Test Description

The numbers below refer to the step numbers on the diagnostic table.

The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the Freeze Frame and Failure Records data on the scan tool if applicable. This creates an electronic copy of the data captured when this DTC set. The scan tool stores this data for later reference.

This step simulates a DTC P0118. The PCM and the ECT wiring are OK if the PCM senses the change in the ECT sensor signal.

Reprogram the replacement PCM and perform the Crankshaft Position System Variation Learn Procedure. Refer to the latest Techline information for PCM programming.

Step	Action	Values	Yes	No
1	Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?	--	Go to Step 2	Go to Powertrain On Board Diagnostic (OBD) System Check
2	Turn ON the ignition, with the engine OFF. Install a scan tool. Is the ECT sensor value more than the specified value?	130°C (266°F)	Go to Step 4	Go to Step 3
3	Review the Freeze Frame data and record the parameters. Start the engine. Operate the vehicle within the Freeze Frame conditions and Conditions for Setting this DTC. Is the ECT sensor value more than the specified value?	130°C (266°F)	Go to Step 4	Go to Diagnostic Aids
4	Turn OFF the ignition. Disconnect the ECT sensor electrical connector. Turn ON the ignition, with the engine OFF. Is the ECT sensor value less than the specified value?	-30°C (-22°F)	Go to Step 6	Go to Step 5
5	Turn OFF the ignition. Check the ECT sensor signal circuit for a short to ground. Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems. Was a repair necessary?	--	Go to Step 10	Go to Step 8
6	Turn OFF the ignition. Check for a poor electrical terminal connection at the ECT sensor. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you find a condition?	--	Go to Step 10	Go to Step 7
7	Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Is the action complete?	--	Go to Step 10	--
8	Turn OFF the ignition. Check for a poor electrical terminal connection. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you find a condition?	--	Go to Step 10	Go to Step 9
9	Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete?	--	Go to Step 10	--
10	Use the scan tool in order clear the DTCs. Start the engine. Idle the engine at the normal operating temperature. Operate the vehicle within the Conditions for Setting this DTC as specified in the supporting text. Does the scan tool indicate that this diagnostic Ran and Passed?	--	Go to Step 11	Go to Step 2
11	Check to see if any additional DTCs are set. Does the scan tool display any DTCs that you have not diagnosed?	--	Go to applicable DTC table	System OK