Circuit Description
The engine coolant temperature (ECT) sensor uses a thermistor to control the signal voltage to the powertrain control module (PCM). The PCM applies a voltage on CKT 410 to the sensor. When the engine is cold, the sensor resistance is high, therefore, PCM terminal J1-08 voltage will be high.
As the engine warms, the sensor resistance becomes less and the voltage drops. At normal engine operating temperature, the voltage will measure between 1.5 V to 2 V at PCM terminal J1-08.
The engine coolant temperature sensor is one of the inputs used to control:
| • | The fuel delivery |
| • | The torque converter clutch (TCC) |
| • | The ignition control (IC) |
| • | The evaporative emission (EVAP) canister purge valve |
| • | The idle air control (IAC) |
| • | The electric cooling fan |
Conditions for Setting the DTC
| • | DTC P0117 is not set. |
| • | The engine coolant temperature sensor is out of a calibrated range for 10 out of a 100 samples. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after passing three consecutive diagnostic test. |
| • | A history DTC P1114 will clear after 40 consecutive ignition cycles have occurred without a fault. |
| • | History and current DTC P1114 can be cleared by using the scan tool. |
Diagnostic Aids
| • | If a DTC P1114 cannot be duplicated, the information included in the freeze frame data can be useful. Use the freeze frame data to determine how many ignition cycles have passed since last set. |
| • | Inspect the wiring and connector for proper mating or damage. |
| • | Move the ECT sensor harness and circuitry while observing the scan tool Any circuit that causes the scan tool reading to vary should be thoroughly inspected for the problem causing the condition. |
| • | Inspect the CKT 417 to connect terminal H6 for a short to voltage or a short to ground. |
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Controls Schematics | |||
1 | Was the On-Board Diagnostic (OBD) System Check performed | Go to Step 2 | |
2 | Install a scan tool. Is the DTC P0117 also set? | Go to appropriate DTC chart first | Go to Step 3 |
3 | Check for a poor ECT signal circuit terminal connection at the ECT sensor. Refer to Troubleshooting Procedures in the Electrical Diagnosis section. Was a problem found? | Go to Step 5 | Go to Step 4 |
4 | Check the ECT signal circuit between the ECT sensor connector and the PCM for an intermittent open or short to ground. Refer to Troubleshooting Procedures in the Electrical Diagnosis section. Was a problem found? | Go to Step 6 | Go to Diagnostic Aids |
5 | Replace the faulty harness connector terminal in the ECT sensor signal circuit. Refer to Repair Procedures in Electrical Diagnosis section. Is the action complete? | Repair complete. If a driveability symptom still exists, Go to Symptoms Section 6E3-B | -- |
6 | Repair the intermittent open/short circuit in the wiring harness as necessary. Refer to Repair Procedures in the Electrical Diagnosis section. Is the action complete? | Repair complete. If a driveability symptom still exists, Go to Symptoms Section 6E3-B | -- |
