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For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 1999 🢒 S/T Isuzu - 2WD 🢒 Engine 🢒 Engine Controls - 2.2L 🢒 DTC P0117 Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage

Object Number: 50791 Size: SF
Engine Controls Components
Cell 20: 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 greater 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 two 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 malfunction indicator lamp (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.
    • Use a scan tool to clear the DTCs.

Diagnostic Aids

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

Test Description

The number(s) below refer(s) to the step number(s) 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.

    2.

  2. 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.

    3.

  3. Reprogram 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 and the Crankshaft Position System Variation Learn for the Crankshaft Position System Variation Learn Procedure.

DTC P0117 - Engine Coolant Temperature (ECT) Circuit - Low Voltage

Step

Action

Value(s)

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
  1. Turn ON the ignition switch leaving the engine OFF.
  2. Install a scan tool.

Is the ECT sensor value greater than the specified value?

130°C (266°F)

Go to Step 4

Go to Step 3

3
  1. Review the Freeze Frame data and record the parameters.
  2. Start the engine.
  3. Operate the vehicle within the Freeze Frame conditions and Conditions For Setting this DTC.

Is the ECT sensor value greater than the specified value?

130°C (266°F)

Go to Step 4

Go to Diagnostic Aids

4

  1. Turn OFF the ignition switch.
  2. Disconnect the ECT sensor electrical connector.
  3. Turn ON the ignition switch leaving 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
  1. Turn OFF the ignition switch.
  2. Check the ECT sensor signal circuit for a short to ground.
  3. Repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 8

Go to Step 7

6
  1. Turn OFF the ignition switch.
  2. Check for a poor electrical terminal connection at the ECT sensor.
  3. If the electrical connection is OK, replace the ECT sensor. Refer to the Engine Coolant Temperature Sensor Replacement .

Is the action complete?

--

Go to Step 8

--

7

  1. Turn OFF the ignition switch.
  2. Check for a poor electrical terminal connection.
  3. If the electrical connection is OK, replace the PCM. Refer to the Powertrain Control Module Replacement .

Is the action complete?

--

Go to Step 8

--

8
  1. Using the scan tool, clear the DTCs.
  2. Start the engine.
  3. Idle the engine at the normal operating temperature.
  4. 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 9

Go to Step 2

9

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