For 1990-2009 cars
Engine Controls Components
Engine Data Sensors, A/C Refrig Press, TP, MAP, ECT, IAT
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

### 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

• | DTCs P0101, P0102, P0103, P0107, P0108, P0117, P0118, P0125, 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 PCM will not illuminate the malfunction indicator lamp (MIL).

• | The PCM will store conditions which were present when the DTC set as Failure Records data only. This information will not be stored as Freeze Frame data.

### Conditions for Clearing the MIL/DTC

• | A History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

• | The DTC can be cleared by using the scan tool Clear Info function.

### 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.

1. 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.

2. 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. Refer to Engine Cooling for cooling system precautions and service procedures.

   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 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Are any other DTCs set? | -- | Go to DTCs that are set | Go to Step 3
3 | Verify proper operation of the ECT and IAT sensor by performing the following:

1. Allow the engine and vehicle temperature to stabilize to that of the ambient (outside) air temperature.

Allowing the vehicle to stabilize overnight will ensure the most accurate results.

2. Turn the Key ON but DO NOT start the engine.

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

4 |

1. Place an accurate thermometer near the location of the IAT sensor.

Allow the thermometer temperature to stabilize.

2. Compare the thermometer reading to the IAT sensor temperature displayed on the scan tool.

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 | --