P0118-ENGINE COOLANT TEMPERATURE SENSOR CIRCUIT HIGH
For a complete wiring diagram, refer to the Wiring Information.
Thoery of operation
The Engine Coolant Temperature (ECT) sensor is a variable resistor that measures the temperature of the engine coolant. The Powertrain Control Module (PCM) supplies 5 Volts to the ECT signal circuit and supplies a ground to the low reference circuit.
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When Monitored:
With the ignition on. Battery voltage greater than 10.4 Volts.
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Set Condition:
The Powertrain Control Module (PCM) detects that the Engine Coolant Temperature Sensor input voltage is above the maximum acceptable value. One Trip Fault. Three good trips to turn off the MIL. The MIL and ETC light will illuminate if equipped.
Possible Causes |
|---|
| (K2) ECT SIGNAL CIRCUIT SHORTED TO VOLTAGE |
| (K2) ECT SIGNAL CIRCUIT OPEN |
| (K900) SENSOR GROUND CIRCUIT OPEN |
| ENGINE COOLANT TEMPERATURE (ECT) SENSOR |
| POWERTRAIN CONTROL MODULE (PCM) |
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
| 1. | Start the engine and allow it to reach normal operating temperature. |
When the engine is operating, do
not stand in direct line with the fan. Do not put your hands near
the pulleys, belts or fan. Do not wear loose clothing. Failure to
follow these instructions may result in possible serious or fatal
injury.
WARNING:
| NOTE: | Diagnose and repair any system voltage DTCs before continuing with this test. |
| 2. | With the scan tool, select View DTCs. |
Is the DTC Active at this time?
Yes
- Go To 2
No
- Perform the INTERMITTENT CONDITION diagnostic procedure. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
2. (K2) ECT SIGNAL CIRCUIT SHORTED TO VOLTAGE
 |
| 1. | Turn the ignition off. |
| 2. | Disconnect the ECT Sensor harness connector. |
| 3. | Disconnect the PCM C2 harness connector. |
| 4. | Ignition on, engine not running. |
| 5. | Measure the voltage on the (K2) ECT Signal circuit in the ECT Sensor harness connector. |
Is there any voltage present?
Yes
- Repair the short to voltage in the (K2) ECT Signal circuit.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
No
-
Go To 3
3. (K2) ECT SIGNAL CIRCUIT OPEN
| 1. | Turn the ignition off. |
Do not probe the PCM harness connectors. Probing the PCM harness
connectors will damage the PCM terminals resulting in poor terminal
to pin connection. Install the GPEC Diagnostic Adaptor to perform
the diagnosis.
CAUTION:
| 2. | Connect the Adapter, GPEC Diagnostic 10436 . |
| 3. | Measure the resistance of the (K2) ECT Signal circuit from the ECT Sensor harness connector to the GPEC Adaptor. |
Is the resistance below 5.0 Ohms?
Yes
- Go To 4
No
- Repair the open in the (K2) ECT Signal circuit.
-
Perform the POWERTRAIN
VERIFICATION TEST. (Refer to
28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM)
- Standard
Procedure).
4. (K900) SENSOR GROUND CIRCUIT OPEN
| 1. | Measure the resistance of the (K900) Sensor ground circuit from the ECT Sensor harness connector to the GPEC Adaptor. |
Is the resistance below 5.0 Ohms?
Yes
- Go To 5
No
- Repair the open or excessive resistance in the (K900) Sensor ground circuit.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
 |
| 1. | Reconnect the PCM C2 harness connector. |
| 2. | Connect a jumper wire between the (K2) ECT Signal circuit and the (K900) Sensor ground circuit in the ECT harness connector. |
| 3. | Turn the ignition on. |
| 4. | With the scan tool, read ECT voltage. |
| NOTE: | The sensor voltage should be approximately 0.0 Volts (plus or minus .1 Volt) with the jumper wire in place. |
Does the scan tool display the voltage as described above?
Yes
- Verify that there is good pin to terminal contact in the ECT Sensor and Powertrain Control Module connectors. If OK, replace the Engine Coolant Temperature Sensor. (Refer to 07 - Cooling/Engine/SENSOR, Coolant Temperature - Removal) .
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
No
-
Go To 6
NOTE: Remove the jumper wire before continuing.
6. POWERTRAIN CONTROL MODULE (PCM)
| 1. | Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the ECT Sensor and the Powertrain Control Module (PCM). |
| 2. | Look for any chafed, pierced, pinched or partially broken wires. |
| 3. | Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the ECT Sensor and Powertrain Control Module connectors. |
| 4. | Perform any Technical Service Bulletins that may apply. |
Were there any problems found?
Yes
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).
No
- Replace and program the Powertrain Control Module in accordance with the Service Information. (Refer to 08 - Electrical/8E - Electronic Control Modules/MODULE, Powertrain Control - Removal) .
- Perform the POWERTRAIN VERIFICATION TEST. (Refer to 28 - DTC-Based Diagnostics/MODULE, Powertrain Control (PCM) - Standard Procedure).