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DTC P0125: Engine Coolant Temperature (ECT) Insufficient for Closed Loop Fuel Control: Troubleshooting

TROUBLESHOOTING CHART

Step Action Value (s) Yes No
1 Perform an On-Board Diagnostic (OBD II) System Check.
Is the system check complete?		 - Go to Step 2 Go to On-Board Diagnostic (OBD II) System Check
2
  1. Turn the ignition ON, with the engine OFF.
  2. Install a scan tool.

Does the scan tool display and additional Diagnostic Trouble Codes (DTCs) set P0117 or P0118?		 - Go to applicable DTC table Go to Step 3
3
  1. Allow the engine to cool fully to ambient temperature.
  2. Compare the Engine Coolant Temperature (ECT) sensor reading to the Intake Air Temperature (IAT) sensor readings.

Are the temperature reading close?		 - Go to Step 5 Go to Step 4
4
  1. Disconnect the ECT sensor electrical connector.
  2. Using a Digital Voltmeter (DVM), measure the resistance across the ECT sensor terminal 1 and 2.
  3. Check the ECT sensor value to actual coolant temperature using the Temperature vs. Resistance table.

Does the ECT sensor accurately reflect the actual engine coolant temperature?		 - Go to Step 5 Go to Step 9
5 Disconnect the ECT sensor electrical connector.
Is the ECT sensor value less than the specified value?		 -30 ° C (-22 ° F) Go to Step 6 Go to Step 8
6 Jumper the ECT sensor signal circuit, terminal 1 and sensor ground circuit, terminal 2 together at the ECT sensor connector.
Is the ECT sensor value greater than the specified value?		 130 ° C (266 ° F) Go to Diagnostic Aids Go to Step 7
7 Check the ECT sensor electrical connector terminals 2 and 1 and the Engine Control Module (ECM) electrical terminals E25 and E51 for poor connectors or malfunctioning terminals and repair as necessary.
Is the repair complete?		 - Go to Step 10 Go to Step 8
8
  1. Turn the ignition OFF.
  2. Replace the ECM.

Is the action complete?		 - Go to Step 10 -
9
  1. Turn the ignition OFF.
  2. Replace the ECT sensor.

Is the action complete?		 - Go to Step 10 -
10
  1. Using the scan tool, clear the Diagnostic Trouble Codes (DTCs).
  2. Start the engine and idle at normal operating temperature.
  3. Operate the vehicle within the Conditions for setting this DTC as specified in the supporting text.

Does the scan tool indicate that this diagnostic ran and passed?		 - Go to Step 11 Go to Step 2
11 Check if any additional DTCs are set.
Are any DTCs displayed that have not been diagnosed?		 - Go to applicable DTC table System OK
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