Circuit Description
The Engine Coolant Temperature (ECT) sensor is a thermistor that controls signal voltage to the PCM. When the engine is cold, the sensor resistance is high, therefore the PCM will see high signal voltage. As the engine warms, sensor resistance becomes less and voltage drops. The voltage measured across the thermister is interpreted as a temperature. This is a type B DTC.
Conditions for Setting the DTC
Engine coolant temperature greater than or equal to 151°C (304°F) for 2 seconds.
Action Taken When the DTC Sets
| • | High idle |
| • | No TCC |
| • | Shift schedules will be affected. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the MIL off after three consecutive trips without a fault condition. |
| • | A History DTC will clear when forty consecutive warm-up cycles that the diagnostic does not fail (coolant temperature has risen 5°C (40°F) from start up coolant temperature and engine coolant temperature exceeds 71°C (160°F) that same ignition cycle. |
| • | Use of a Scan Tool |
Diagnostic Aids
Check harness routing for a potential short to ground. After engine is started, the ECT temperature should rise steady to about 85°C (185°F). A mis-scaled sensor could result in poor driveability complaints.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
If the fault is still present, the engine coolant voltage will greater than 151°C (304°F).
-
This test simulates a DTC P0117. If the PCM recognizes the high signal voltage (low temperature) the PCM and the wiring are okay.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 |
Important: Before clearing the DTCs, use the scan tool to record the Freeze Frame and the Failure Records for reference. This data will be lost when the Clear Info function is used. Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to A Powertrain On Board Diagnostic (OBD) System Check | |
Does the scan tool display an ECT greater than the specified value? | 151°C (304°F) | |||
Does the scan tool display an ECT less than or equal to the specified value? | -40°C (-40°F) | |||
4 |
Is the resistance at the specified value? | ∞ | ||
5 | The DTC is intermittent. If no additional DTCs are stored, refer to the Diagnostic Aids. If the additional DTCs are stored, refer to those tables first. | -- | Go to The Applicable DTC Table | |
6 | Repair the short to the ground in the ECT signal circuit. Refer to Wiring Repairs in Engine Electrical. Is the action complete? | -- | -- | |
7 | Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Is the replacement complete? | -- | -- | |
8 | Replace the PCM. Important: If the PCM is faulty, reprogram the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the replacement complete? | -- | -- | |
9 |
Does the scan tool indicate that this diagnostic ran and passed? | -- | ||
10 | Using the scan tool, select the Capture Info and the Review Info. Are any DTCs displayed that have not been diagnosed? | -- | Go to The Applicable DTC Table | System OK |
