P0117-ENGINE COOLANT TEMPERATURE SENSOR CIRCUIT LOW
For a complete wiring diagram, refer to the Wiring Information.
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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 below the minimum acceptable value. One Trip Fault. Three good trips to clear the MIL. The MIL and ETC light will illuminate if equipped.
Possible Causes |
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| (K2) ECT SIGNAL CIRCUIT SHORTED TO GROUND |
| (K2) ECT SIGNAL CIRCUIT SHORTED TO THE (K915) SENSOR GROUND CIRCUIT |
| 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).
| 1. | Turn the ignition off. |
| 2. | Disconnect the ECT harness connector. |
| 3. | Ignition on, engine not running. |
| 4. | With the scan tool, read ECT voltage. |
| NOTE: | The sensor voltage should be approximately 5.0 Volts (plus or minus .1 Volt) with the connector disconnected. |
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 ECT 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 3
3. (K2) ECT SIGNAL CIRCUIT SHORTED TO THE (K900) SENSOR GROUND CIRCUIT
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| 1. | Turn the ignition off. |
| 2. | Disconnect the PCM C2 harness connector. |
| 3. | Measure the resistance between the (K900) Sensor ground circuit and the (K2) ECT Signal circuit in the ECT Sensor harness connector. |
Is the resistance below 5.0 Ohms?
Yes
- Repair the short between the (K900) Sensor ground circuit and 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 4
4. (K2) ECT SIGNAL CIRCUIT SHORTED GROUND
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| 1. | Measure the resistance between ground and the (K2) ECT Signal circuit in the ECT Sensor harness connector. |
Is the resistance below 100 Ohms?
Yes
- Repair the short to ground 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 5
5. 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).