Circuit Description
The PCM will richen the air/fuel ratio when a high coolant temperature is monitored. Called Hot Fuel Enrichment (HFE) this condition can cause exhaust emissions to exceed the federal emissions standards for this vehicle. This DTC is required in order to prevent HFE from being active during a skewed ECT sensor condition or during an actual cooling system condition that results in hot engine coolant. The PCM will calculate an engine coolant temperature value based on IAT, engine speed, vehicle speed and engine load. If the ECT sensor value is higher than the calculated coolant temperature during the Conditions for Running the DTC, this DTC sets and HFE is disabled.
Conditions for Running the DTC
| • | DTC's P0101, P0102, P0103, P0107, P0108, P0117, P0118, P0125, P0502, or P1108 are not set. |
| • | Key ON engine coolant temperature is the same or less than 110°C. |
| OR |
| The engine coolant temperature goes less than 104°C anytime after key ON. |
| • | Intake Air Temperature, Engine Load, Engine Speed and Vehicle Speed are all within a specific range. |
Conditions for Setting the DTC
The PCM determines the monitored engine coolant temperature (from the ECT sensor) is more than the calculated coolant temperature.
Action Taken When the DTC Sets
| • | The Malfunction Indicator Lamp (MIL) will not illuminate. |
| • | No message will be displayed. |
Conditions for Clearing the MIL/DTC
| • | A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test. |
| • | A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail. |
| • | Use a scan tool to clear DTCs. |
| • | Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation. |
Diagnostic Aids
The most likely cause of this DTC is a cooling system problem. Perform the Cooling Fan Functional Check in this section and also visually inspect the cooling system for problems such as restricted radiator AIR flow. Refer to Engine Cooling for cooling system diagnosis.
Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
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It is critical that the sensors are accurate to within 1 degree. The engine must be allowed to cool completely. Depending on conditions this will take a minimum of 6 hours.
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The IAT sensor must indicate the actual ambient temperature to within 1 degree. If the IAT sensor is accurate the ECT sensor must be inaccurate.
Further checks of the ECT sensor can be made by comparing actual coolant temperature to the ECT scan tool display.
Obtain actual coolant temperature using a thermometer located in the engine coolant. A check of the ECT sensor's resistance may also be performed using the Temperature Versus Resistance Specifications table.
If the actual coolant temperature is the same as the ECT scan tool display then the engine was not allowed to cool completely. Allow the vehicle to cool and repeat the diagnostic table.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | |
2 | Are any other DTC's set? | -- | Go to DTC's that are set | Go to Step 3 |
Verify proper operation of the ECT and IAT sensor by performing the following:
Allowing the vehicle to stabilize overnight will ensure the most accurate results. Using a scan tool compare the ECT and IAT sensors. If both sensors do not indicate exactly the same temperature one of the sensors is inaccurate. Do both sensors indicate the same temperature? | -- | Go to Diagnostic Aids | Go to Step 4 | |
Allow the thermometer temperature to stabilize. Refer to Test Descriptions. Is the IAT sensor responding correctly to actual ambient temperature? | Go to Step 5 | Go to Step 6 | ||
5 | Replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . Is the replacement complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
6 | Replace the IAT sensor. Refer to Intake Air Temperature Sensor Replacement . Is the replacement complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
