DTC Descriptor
DTC P0117: Engine Coolant Temperature Circuit Low InputDTC P0118: Engine Coolant Temperature Circuit High Input
DTC P1258: Engine Coolant Over Temperature Fuel Disabled
Diagnostic Fault Information
Perform the Diagnostic System Check - Vehicle , prior to using this diagnostic procedure.
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
ECT Sensor Signal | P0117 | P0118, P0119 | P0118, P0119¹ | P0116 |
Low Reference | -- | P0118, P0119 | P0118, P0119¹ | P0116 |
¹ Sensor or ECM damage may occur if the circuit is shorted to B+ | ||||
Typical Scan Tool Data
Circuit | Short to Ground | Open | Short to Voltage |
|---|---|---|---|
Operating Conditions: Engine operating in Closed Loop. Parameter Normal Range: -39°C to 142°C (-38° to 288°F) Varies with coolant temperature. | |||
ECT Sensor Signal | 143°C (289°F) | -40°C (-40°F) | -40°C (-40°F)¹ |
Low Reference | -- | -40°C (-40°F) | -40°C (-40°F)¹ |
¹ Internal ECM or ECT sensor damage may occur if the circuit is shorted to B+ | |||
Circuit Description
The engine coolant temperature (ECT) sensor is a variable resistor that measures the temperature of the engine coolant. The engine control module (ECM) supplies 5 volts to the ECT signal circuit and supplies a ground to the low reference circuit.
The following table illustrates the difference between temperature, resistance and voltage:
ECT | ECT Resistance | ECT Signal Voltage |
|---|---|---|
Cold | High | High |
Warm | Low | Low |
Conditions for Running the DTC
P0117
| • | The engine is operating. |
| • | The start up intake air temperature (IAT) is less than 72°C (161°F). |
| • | The DTC runs continuously once the above condition is met. |
P0118
| • | The start up intake air temperature (IAT) is more than 72°C (161°F). |
| • | The engine run time is more than 59 seconds. |
| • | The DTC runs continuously once the above condition are met. |
P1258
| • | The ignition is ON or the engine is operating. |
| • | The DTC runs continuously once the above condition is met. |
Conditions for Setting the DTC
P0117
The ECM detects that the ECT is more than 140°C (284°F) for more than 4 seconds.
P0118
The ECM detects that the ECT is less than -42°C (-43.6°F) for more than 4 seconds. The scan tool is limited to -40°C (-40°F), so the diagnostic procedure uses -39°C (-38°F) to determine if there is an ECT condition.
P1258
The ECM detects that the ECT is greater than 1312°C (268°F) for longer than 2 seconds.
Action Taken When the DTC Sets
DTCs P0117, P0118 and P1258 are type B DTCs.
Conditions for Clearing the MIL/DTC
DTCs P0117, P0118 and P1258 are type B DTCs.
Diagnostic Aids
| • | Test the ECT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor can result in a DTC or a driveability condition. Refer to Temperature Versus Resistance - Engine Coolant Temperature Sensor . |
| • | If the vehicle has sat overnight, the IAT sensor and the ECT sensor values should display within 3°C (5°F). |
| • | After starting a cold engine the ECT sensor temperature should rise steadily then stabilise after the thermostat opens. |
| • | High resistance in the circuits of either the ECT or IAT sensor may set a DTC. |
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Circuit/System Verification
Engine idling for 1 minute. Observe the DTC information with a scan tool. DTC P0117, P0118 and P1258 should not set.
Circuit/System Testing
- Ignition OFF, disconnect the ECT sensor.
- Ignition ON, verify that the ECT sensor parameter is at -40°C (-40°F).
- Test for less than 5 volts between the low reference circuit terminal and a known ground.
- Ignition OFF, remove the fuse that supplies B+ to the ECM.
- Test for less than 5 ohms between the low reference circuit terminal and a known ground.
- Install the fuse that supplies B+ to the ECM.
- Ignition ON, install a 3-A fusible link wire between the signal circuit terminal and the low reference circuit terminal, Verify the ECT sensor parameter is greater than 142°C (288°F).
- If all circuits test normal, replace the ECT sensor.
| ⇒ | If greater than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit test normal, replace the ECM. |
Notice: Do NOT use a test lamp to test the continuity of the circuit. Damage to the control module may occur due to excessive current draw.
Important:
• The ECT sensor shares its low reference circuit with other sensors. If
the low reference circuit internal to the ECM is open, 1-5 volts will
be measured on the low reference circuit due to a backfeed condition through the other
sensors. • The control module or the sensor may be damaged if the circuit is shorted
to B+.
| ⇒ | If greater than the specified range, test low reference circuit for a short to B+, if circuit test normal, replace the ECM. |
| ⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit test normal, replace the ECM. |
| ⇒ | If less than specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM. |
Component Testing
- Ignition OFF, disconnect the harness connector of the engine coolant temperature (ECT) sensor.
- Test the ECT sensor by varying the sensor temperature while monitoring the sensor resistance. Compare the readings with the Temperature Versus Resistance - Intake Air Temperature Sensor . Verify that the resistance is within 5 percent of the specification.
Important: A thermometer can be used to test the sensor off the vehicle.
| ⇒ | If the resistance vs temperature is not within 5 percent, replace the ECT sensor. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
