DTC P0118. Isuzu Isuzu MD F-Series 2004

For 1990-2009 cars only

Makes 🢒 Isuzu 🢒 2004 🢒 Isuzu MD F-Series 🢒 Engine 🢒 Engine Controls - 7.8L 🢒 DTC P0118

DTC P0118 Without RPO CTF

Circuit Description

The engine coolant temperature (ECT) sensor is a variable resistor, sometimes called a thermistor, that measures the temperature of the engine coolant. The engine control module (ECM) supplies 5 volts to the ECT signal circuit. When the ECT is cold, the sensor resistance is high. When the ECT increases, the sensor resistance lowers. With high sensor resistance, the ECM detects a high voltage on the ECT signal circuit. With lower sensor resistance, the ECM detects a lower voltage on the ECT signal circuit. If the ECM detects an excessively high ECT signal voltage, which is a low temperature indication, this DTC will set.

Conditions for Running the DTC

The engine has been running for more than 8 minutes.

Conditions for Setting the DTC

The ECT sensor temperature is less than -39°C (-38°F) for 20 seconds.

Action Taken When the DTC Sets

The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

Conditions for Clearing the MIL/DTC

•	The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

•	A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

•	Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

•	If a short to a separate 5-volt source occurs, this DTC may set. If this is the problem, a continuity test to all other ECM circuits will be necessary in order to diagnose the specific circuit.

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

•	Use the Temperature vs. Resistance table in order to test the ECT sensor at various temperature levels and in order to evaluate the possibility of a skewed sensor. A skewed sensor could result in poor driveability conditions. Refer to Temperature Versus Resistance .

•	If the condition is suspected of being intermittent, refer to Intermittent Conditions .

Test Description

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

If DTC P0118 can only be repeated by duplicating the Failure Records, refer to the Temperature vs Resistance table. The table may be used to test the ECT sensor at various temperatures to evaluate the possibility of a shifted sensor that may be shorted above or below a certain temperature. If this is the case, replace the ECT sensor. If the ECT sensor appears to be OK, the malfunction is intermittent. Refer to Diagnostic Aids.

This step tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.

The ECM in this vehicle use an electrically erasable programmable read-only memory (EEPROM). If the ECM is replaced, the new ECM must be programmed.

Step

Action

Values

Yes

Schematic Reference: Engine Controls Schematics

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

Install a scan tool.
Turn ON the ignition, with the engine OFF.
Use the scan tool in order to observe the ECT sensor temperature.

Is the ECT sensor temperature less than the specified value?

-38°C (-36°F)

Go to Step 4

Go to Step 3

Observe the Freeze Frame/Failure Records data for this DTC.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC or as closely as possible to the Freeze Frame/Failure Records conditions.

Does the DTC reset?

Go to Step 4

Go to Diagnostic Aids

Turn OFF the ignition.
Disconnect the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement .
Connect a 3-amp fused jumper between the signal circuit of the ECT sensor and the low reference circuit. Refer to Using Fused Jumper Wires in Wiring Systems.
Turn ON the ignition, with the engine OFF.
Use the scan tool in order to observe the ECT sensor temperature.

Is the ECT sensor temperature more than the specified value?

138°C (280°F)

Go to Step 8

Go to Step 5

Turn OFF the ignition.
Connect a 3-amp fused jumper between the signal circuit of the ECT sensor and ground.
Turn ON the ignition, with the engine OFF.
Use the scan tool in order to observe the ECT sensor temperature.

Is the ECT sensor temperature more than the specified value?

138°C (280°F)

Go to Step 7

Go to Step 6

Test the signal circuit of the ECT sensor for the following conditions:

•	A short to voltage

•	A high resistance

•	An open circuit

Repair the circuit as necessary. Refer to Circuit Testing , and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 9

Test the reference low circuit of the ECT sensor for a high resistance or an open.
Repair the circuit as necessary. Refer to Circuit Testing , and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 9

Test the signal circuit of the ECT sensor for the following conditions:

•	A short to voltage

•	Any poor connections at the harness connector of the ECT sensor.

Repair the connections as necessary. Refer to Circuit Testing and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 10

Inspect for poor connections at the harness connector of the ECM. Refer to Engine Control Module Replacement/Restore Fuel Rate Data .
Repair the connections as necessary. Refer to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 11

Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement .

Did you complete the replacement?

Go to Step 12

Replace the ECM. Refer to Engine Control Module Replacement/Restore Fuel Rate Data .

Did you complete the replacement?

Go to Step 12

Use the scan tool in order to clear the DTCs.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

Go to Step 13

Go to Step 2

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

Go to Diagnostic Trouble Code (DTC) List

System OK

DTC P0118 With RPO CTF

Circuit Description

Conditions for Running the DTC

•	The ignition is ON.

•	The battery voltage is between 10-16 volts.

Conditions for Setting the DTC

The ECM detects that the ECT signal voltage is more than 4.95 volts.

Action Taken When the DTC Sets

•	The ECM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.

•	The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records.

•	The ECM uses an ECT value of -29°C (-20.2°F) for engine starting.

•	The ECM uses an ECT value of 0°C (32°F) for engine running.

•	The ECM closes the exhaust gas recirculation (EGR) valve.

•	The ECM disables oil pressure sensor diagnostics.

Condition for Clearing the DTC

•	A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

•	Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

•	After starting the engine, the ECT should rise steadily to about 80°C (176°F), then stabilize when the thermostat opens.

•	Use the Temperature vs. Resistance table to test the ECT sensor at various temperature levels to evaluate the possibility of a skewed sensor. A skewed sensor could result in poor driveability concerns. Refer to Temperature Versus Resistance .

•	If an intermittent condition is suspected, refer to Intermittent Conditions .

Test Description

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

This step tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.

Step

Action

Values

Yes

Schematic Reference: Engine Controls Schematics

Did you perform the Diagnostic System Check - Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

Observe the Failure Records for this DTC.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 3

Go to Diagnostic Aids

Turn OFF the ignition.
Disconnect the engine coolant temperature (ECT) sensor connector.
Connect a DMM between the signal circuit and the low reference circuit of the ECT sensor harness.
Turn ON the ignition, with the engine OFF.

Is the DMM voltage more than the specified range?

4.5-5.5 V

Go to Step 4

Go to Step 5

Important: The ECT sensor may be damaged if the circuit is shorted to a voltage source.

Test the signal circuit for a short to voltage circuit.
Repair the circuits, as necessary.

Did you find and correct the condition?

Go to Step 13

Go to Step 12

Turn OFF the ignition.
Disconnect the ECT sensor connector.
Connect a 3-amp fused jumper wire between the signal circuit of the ECT sensor and the low reference circuit at the ECT sensor.
Turn ON the ignition, with the engine OFF.
Observe the ECT Sensor parameter with a scan tool.

Is the ECT Sensor parameter more than the specified value?

120°C (248°F)

Go to Step 9

Go to Step 6

Turn OFF the ignition.
Connect a 3-amp fused jumper wire between the signal circuit of the ECT sensor and a known good ground.
Turn ON the ignition, with the engine OFF.
Observe the ECT Sensor parameter with a scan tool.

Is the ECT Sensor parameter more than the specified value?

120°C (248°F)

Go to Step 8

Go to Step 7

Test the signal circuit between the engine control module (ECM) and the ECT sensor for the following conditions:

•	An open circuit

•	High resistance

Repair the circuits, as necessary.

Did you find and correct the condition?

Go to Step 13

Go to Step 10

Test the low reference circuit between the ECM and the ECT sensor for the following conditions:

•	An open circuit

•	High resistance

Repair the circuits, as necessary.

Did you find and correct the condition?

Go to Step 13

Go to Step 10

Turn OFF the ignition.
Disconnect the ECT sensor.
Inspect for poor connections at the harness connector of the ECT sensor.
Repair the circuits, as necessary.

Did you find and correct the condition.

Go to Step 13

Go to Step 11

Turn OFF the ignition.
Disconnect the ECM sensor.
Inspect for poor connections at the harness connector of the ECM.
Repair the circuits, as necessary.

Did you find and correct the condition.

Go to Step 13

Go to Step 12

Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement .

Did you complete the replacement?

Go to Step 13

Important: The new ECM must be programmed.

Replace the ECM. Refer to Engine Control Module Replacement/Restore Fuel Rate Data .

Did you complete the replacement?

Go to Step 13

Clear the DTCs with a scan tool.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 2

Go to Step 14

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

Go to Diagnostic Trouble Code (DTC) List

System OK