P0117
DTC P0117 Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage
Circuit Description
The Engine Coolant Temperature (ECT) sensor is a thermistor that controls the signal voltage to the Powertrain Control Module (PCM). The PCM supplies a 5 volt reference circuit and a ground circuit to the ECT sensor. When 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 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 has been running for 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 control module illuminates the malfunction indicator lamp (MIL) if a failure is detected during 2 consecutive key cycles.
- The control module sets the DTC and records the operating conditions at the time the diagnostic fails. The control module stores the failure information in the scan tool's Freeze Frame and Failure Records.
Conditions for Clearing the MIL/DTC
- The control module turns OFF the MIL after 3 consecutive drive trips during which the diagnostic test Runs and Passes.
- A history DTC clears after 40 consecutive warm-up cycles during which no fault is detected. A warm up cycle occurs when the engine coolant temperature rises 22° C (40° F) above the startup temperature and exceeds 70° C (158° F) during the same ignition cycle.
- The DTCs can be cleared using the scan tool Clear Information function.
Diagnostic Aids
After the engine has started, the ECT should rise steadily to about 90° C (194° F) then stabilize when the thermostat opens.
Steps 1 - 4:
Steps 5 - 7:
Steps 8 - 9:
Test Description
The numbers below refers to the step numbers in the Diagnostic Table.
1. 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.
4. 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.
7. Program the replacement PCM and perform the crankshaft position system variation learn procedure. Refer to the latest Isuzu Technical Communications System (ITCS) information for PCM programming.