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 to 2.0 volts at PCM terminal J1-08.
The engine coolant temperature is one of the inputs used to control:
| • | The fuel delivery |
| • | The torque converter clutch (TCC) |
| • | The ignition control |
| • | The evaporative emission (EVAP) canister purge valve |
| • | The idle air control (IAC) |
| • | The electric cooling fan |
Conditions for Setting the DTC
| • | DTC P0118 is not set. |
| • | The malfunction is present for greater than 10 counts per 100 samples. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after passing three consecutive diagnostic test. |
| • | A history DTC P1115 will clear after 40 consecutive ignition cycles have occurred without a fault. |
| • | A history and current DTC P0117 can be cleared by using the scan tool. |
Diagnostic Aids
| • | If a DTC P1115 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 the last set. |
| • | Inspect the wiring harness 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 condition. |
| • | Inspect CKT 417 to connector 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 | Go to OBD System Check |
2 | Is DTC P0118 also set? | Go to the appropriate DTC chart first | Go to Step 3 |
3 | Is the DTC P0116, P1111, and/or P1121 also set? | Go to Step 6 | |
4 | Check for a poor sensor ground circuit terminal connection at the ECT sensor. Refer to Troubleshooting Procedures in the Electrical Diagnosis section. Was a problem found? | Go to Step 8 | Go to Step 5 |
5 | Check the ECT signal circuit between the ECT sensor connector and the PCM for an intermittent short to voltage. Refer to Troubleshooting Procedures in the Electrical Diagnosis section. Was a problem found? | Go to Step 9 | Go to Step 7 |
6 | Check for a poor sensor ground circuit terminal connection a the PCM. Refer to Troubleshooting Procedure in the Electrical Diagnosis section. Was a problem found? | Go to Step 8 | Go to Step 7 |
7 | Check for an intermittent open or a faulty splice in the sensor ground circuit. Refer to Troubleshooting Procedures in the Electrical Diagnosis section. Was a problem found? | Go to Step 9 | Go to Diagnostic Aids |
8 | Replace the faulty harness connector terminal for the sensor ground circuit. Refer to Repair Procedures in the Electrical Diagnosis section. Is the action complete? | Repair complete. If a driveability symptom still exists, refer to Symptoms | -- |
9 | With a scan tool, select Capture Info in order to observe the stored information. Does the scan tool display any DTCs that you have not diagnosed? | Repair complete. If a driveability symptom still exists, refer to Symptoms | -- |
