DTC P0118 Engine Coolant Temperature (ECT) Sensor Circuit High Voltage. Cadillac Seville 2000

For 1990-2009 cars only

Makes 🢒 Cadillac 🢒 2000 🢒 Seville 🢒 DTC 🢒 DTC P0118 Engine Coolant Temperature (ECT) Sensor Circuit High Voltage

Engine Controls Component Views
Sensors
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The engine coolant temperature (ECT) sensor is a thermistor, or variable resistor, that measures the temperature of the engine coolant. The PCM supplies 5 volts to the ECT signal circuit through a pull-up resistor. When the engine coolant temperature is cold, the sensor resistance is high. When the engine coolant temperature increases, the sensor resistance lowers. With high sensor resistance, the PCM detects a high voltage on the ECT signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the ECT signal circuit. If the PCM detects an excessively high ECT signal voltage (a low temperature indication), DTC P0118 will set.

Conditions for Running the DTC

•	IAT sensor DTCs are not set.

•	The engine has been running for 60 seconds.

•	Intake air temperature is more than -7°C (19°F).

Conditions for Setting the DTC

•	The ECT sensor signal voltage is more than 4.9 volts. The temperature would be approximately -37°C (-35°F).

•	The conditions exists for less than 1 second.

Action Taken When the DTC Sets

•	The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test runs and fails.

•	The PCM stores the conditions present when the DTC set as Freeze Frame/Failure Records data.

Conditions for Clearing the MIL/DTC

•	The PCM will turn the MIL OFF after the third consecutive trip in which the diagnostic runs and passes.

•	The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

•	The DTC can be cleared by using the scan tool Clear DTC Information function.

Diagnostic Aids

For intermittent conditions, refer to DTC P1115 Engine Coolant Temperature (ECT) Sensor Circuit Intermittent High Voltage and/or Symptoms .

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	Connect the scan tool. Turn ON the ignition, with the engine OFF. Observe the ECT sensor display. Does the scan tool indicate ECT below the specified value?	-24°C (-11°F)	Go to Step 4	Go to Step 3
3	Review and record the scan tool Fail Records data. Operate the vehicle within the Fail Records conditions. With the scan tool, monitor the Specific DTC information for DTC P0118 until the test runs. Does the scan tool indicate that DTC P0118 failed last test?	--	Go to Step 4	Go to Diagnostic Aids
4	Turn the ignition to the LOCK position. Disconnect the ECT sensor connector. Turn the ignition to the RUN position with the engine OFF. Using DMM, measure the voltage between the ECT sensor signal and battery ground. Does the DMM indicate a voltage near the specified value?	5V	Go to Step 5	Go to Step 10
5	Install the scan tool. Connect a jumper between the IAT signal and sensor ground circuits. Observe both of the 5 volt reference displays on the scan tool. Do both 5 volt reference displays indicate OK?	--	Go to Step 7	Go to Step 6
6	Locate and repair the short between the ECT signal circuit and 5 volt reference A, or 5 volt reference B. Is the action complete?	--	Go to Step 15	--
7	Leave the jumper connected between the ECT signal and sensor ground circuits in the harness connector. Observe the ECT sensor display on the scan tool. Does the scan tool indicate an ECT sensor display near the specified value?	150°C (302°F)	Go to Step 8	Go to Step 9
8	Test for poor connections at the ECT sensor. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. If the condition is found, repair as necessary. Refer to Repairing Connector Terminals in Wiring Systems Did you find and correct the condition?	--	Go to Step 15	Go to Step 13
9	Turn the ignition to the LOCK position. Disconnect the PCM connector. Test the ECT sensor ground for an open or poor connections at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. If the condition is found, repair as necessary. Refer to Repairing Connector Terminals in Wiring Systems. Did you find and correct the condition?	--	Go to Step 15	Go to Step 14
10	Does the DMM indicate a voltage more than the specified value?	5V	Go to Step 11	Go to Step 12
11	Turn the ignition to the LOCK position. Disconnect the PCM connector. Test the ECT sensor signal circuit for a short to voltage. If the condition is found, repair as necessary. Refer to Repairing Connector Terminals in Wiring Systems. Did you find and correct the condition?	--	Go to Step 15	Go to Step 14
12	Turn the ignition to the LOCK position. Disconnect the PCM connector. Test the ECT sensor signal circuit for an open or poor connections at the PCM. Refer to Repairing Connector Terminals in Wiring Systems. If the condition is found, repair as necessary. Refer to Repairing Connector Terminals in Wiring Systems. Did you find and correct the condition?	--	Go to Step 15	Go to Step 14
13	Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Is the action complete?	--	Go to Step 15	--
14	Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete?	--	Go to Step 12	--
15	Review and record the scan tool Fail Records data. Operate the vehicle within the parameters listed in the Conditions for Running the DTC. With the scan tool, monitor the Specific DTC Information for DTC P0118 until the test runs. Does the scan tool indicate that DTC P0118 passed?	--	System OK	Go to Step 2