P0118

DTC P0118

DTC DESCRIPTOR

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

DTC P0118
Engine Coolant Temperature (ECT) Sensor Circuit High Voltage

DIAGNOSTIC FAULT INFORMATION

IMPORTANT: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Testing and Inspection






TYPICAL SCAN TOOL DATA

ECT Sensor Temperatures:

CIRCUIT/SYSTEM DESCRIPTION
The engine coolant temperature (ECT) sensor is a variable resistor, that measures the temperature of the engine coolant. The control module supplies 5 volts to the ECT signal circuit and a ground for the ECT low reference circuit. When the ECT is cold, the sensor resistance is high. When the ECT increases, the sensor resistance decreases. With high sensor resistance, the control module detects a high voltage on the ECT signal circuit. With lower sensor resistance, the control module detects a lower voltage on the ECT signal circuit. If the control module detects an excessively low ECT signal voltage, which is a high temperature indication, DTC P0117 sets. If the control module detects an excessively high ECT signal voltage, which is a low temperature indication, DTC P0118 sets.

CONDITIONS FOR RUNNING THE DTC

P0117
- The engine run time is more than 3 seconds. OR The ignition is ON and the intake air temperature (IAT) is less than 90°C (194°F).
- The diagnostic runs continuously when the above conditions are met.

P0118
- The engine is running for more than 30 seconds. OR The ignition is ON and the intake air temperature (IAT) is more than 0°C (32°F).
- The diagnostic runs continuously when the above conditions are met.

CONDITIONS FOR SETTING THE DTC

P0117
The control module detects that the ECT sensor parameter is more than 139°C (282°F) for more than 24 seconds.

P0118
The control module detects that the ECT sensor parameter is less than -37°C (-35°F) for more than 24 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.
- The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

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.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
- Clear the MIL and the DTC with a scan tool.

DIAGNOSTIC AIDS
- An overheating condition may cause this DTC to set.
- After starting the engine, the ECT sensor temperature should rise steadily to about 90°C (194°F) then stabilize after the thermostat opens.
- If a short to a separate voltage source occurs this DTC may set and damage the ECT sensor.

CIRCUIT/SYSTEM TESTING

IMPORTANT:
- Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Testing and Inspection
- The cooling fans are commanded ON when certain DTCs are set.
- If a short to voltage occurs, the ECT sensor may be damaged.

P0117
With the Ignition ON, and the engine OFF, disconnect the ECT sensor and observe the ECT parameter for -38°C (-36°F).
- If over -38°C (-36°F), test the signal circuit of the ECT sensor for a short to ground or a short to any low reference circuit, or an intermittent and poor connection at the control module. If checks good then replace the ECT sensor.
- If under -38°C (-36°F), test for an intermittent and for a poor connection at the ECT sensor. If checks good then replace the control module.

P0118
With the ignition ON, engine OFF, disconnect the ECT sensor and measure for 5.2 volts from the signal circuit of the ECT sensor to a good round with a DMM.
- If over 5.2 volts, then test the ECT signal circuit for a short to voltage, and test for an intermittent and for a poor connection at the control module. If all test OK then replace the control module.
- If under 5.2 volts, then test the signal circuit, low reference circuit, of the ECT sensor for high resistance or an open, or a short to any 5-Volt reference circuit. If tests OK then replace the ECT sensor.

REPAIR INSTRUCTIONS

IMPORTANT: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.
- Engine Coolant Temperature (ECT) Sensor Replacement
- Control Module References for engine control module (ECM) replacement, setup, and programming Verification Tests