P040F

DTC P040F

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provide an overview of each diagnostic category.

DTC Descriptor
DTC P040F
- Exhaust Gas Recirculation (EGR) Temperature Sensor 1-2 Correlation

Diagnostic Fault Information





Typical Scan Tool Data





Circuit/System Description

The exhaust gas recirculation (EGR) temperature sensors are variable resistors that measures the temperature of the engine coolant. The engine control module (ECM) supplies 5 volts to the signal circuit and a ground for the low reference circuit. The ECM uses this rationality diagnostic to determine if the input from the EGR temperature sensor 1 or EGR temperature sensor 2 is skewed. The ECM will compare the temperature difference between the EGR temperature sensor 1 and the EGR temperature sensor 2 to determine if the temperatures are within an acceptable operating range of each other.

Conditions for Running the DTC

* The engine has been OFF for more than 5 hours.
* The ambient temperature is greater than -7°C (+20°F).
* DTC P040F runs once per key cycle within the above enabling conditions.

Conditions for Setting the DTC

* The ECM detects a temperature difference of greater than 10°C (50°F) between EGR temperature sensors 1 and 2.
* This DTC runs once per key cycle when the above condition is met.

Action Taken When the DTC Sets

DTC P040F is a Type B DTC.

Conditions for Clearing the DTC

DTC P040F is a Type B DTC.

Diagnostic Aids

* A slight to moderate resistance in either signal or low reference circuit can widen the spread between the two EGR temperature sensors and cause this DTC to set.
* An EGR temperature sensor that is skewed lower at various ambient temperatures, due to more resistance than is normal, can widen the spread between the two sensors and cause this DTC to set. Measure and record the resistance of both EGR temperature sensors 1 and 2 at ambient temperature. Compare those measurements to the Temperature Versus Resistance (ECT Sensors) (Temperature Versus Resistance (ECT Sensors))Temperature Versus Resistance (EGR Temperature Sensors) (Temperature Versus Resistance (EGR Temperature Sensors))Temperature Versus Resistance (EGT Sensors) (Temperature Versus Resistance (EGT Sensors))Temperature Versus Resistance (Fuel Temperature Sensor) (Temperature Versus Resistance (Fuel Temperature Sensor))Temperature Versus Resistance (IAT Sensor 1) (Temperature Versus Resistance (IAT Sensor 1))Temperature Versus Resistance (IAT Sensor 2) (Temperature Versus Resistance (IAT Sensor 2)).
* Inspect both EGR temperature sensors terminals for corrosion and for poor connections. It is very important that a thorough inspection of the wiring and connectors be performed. Failure to fully inspect wiring and connectors may result in misdiagnosis, causing part replacement with reappearance of the malfunction.
* EGR temperature sensors may fail while operating under extreme temperatures. Review the Freeze Frame/Failure Records to verify the failure criteria.

Reference Information
Schematic Reference

Engine Controls Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference

Control Module References (Programming and Relearning) for scan tool information

Circuit/System Verification

Important: Determine the ambient temperature by using an accurate thermometer.

1. If the ignition has been OFF for greater than 10 hours, determine which EGR temperature sensor is skewed by comparing EGR temperature Sensor 1 and 2 parameters to the ambient temperature with a scan tool. The readings should be within 11°C (20°F) of each other, and also the ambient temperature.
2. Engine running, observe the scan tool EGR temperature Sensor 1 and 2 parameters. The readings should be between -39 to +400°C (-38 to +752°F), depending on the current ambient temperature and the vehicle operating conditions
3. Engine running, observe the DTC information with a scan tool. DTC P040F should not set.
4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

Important: If you are unable to determine which EGR temperature sensor is skewed, you must perform the Circuit/System Verification first.

1. Ignition OFF, disconnect the harness connector at the affected ECT sensor.
2. Ignition OFF for 90 seconds, test for less than 5 ohms between the low reference circuit terminal B and ground.

• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

3. Ignition ON, verify the scan tool EGR temperature sensor parameter is colder than -39°C (-40°F).

• If greater than the specified range, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the ECM.

4. Install a 3A fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the scan tool ECT parameter is warmer than 890°C (1634°F).

• If colder than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

5. If all circuits test normal, test or replace the affected EGR temperature sensor.

Component Testing

Measure and record the resistance of the EGR temperature sensor 1 and compare those measurements to the Temperature Versus Resistance (ECT Sensors) (Temperature Versus Resistance (ECT Sensors))Temperature Versus Resistance (EGR Temperature Sensors) (Temperature Versus Resistance (EGR Temperature Sensors))Temperature Versus Resistance (EGT Sensors) (Temperature Versus Resistance (EGT Sensors))Temperature Versus Resistance (Fuel Temperature Sensor) (Temperature Versus Resistance (Fuel Temperature Sensor))Temperature Versus Resistance (IAT Sensor 1) (Temperature Versus Resistance (IAT Sensor 1))Temperature Versus Resistance (IAT Sensor 2) (Temperature Versus Resistance (IAT Sensor 2)).

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Engine Control Module Replacement (Service and Repair)
* Exhaust Gas Recirculation Valve Temperature Sensor Replacement - Position 2 (Exhaust Gas Recirculation Valve Temperature Sensor Replacement - Position 2)
* Exhaust Gas Recirculation Valve Temperature Sensor Replacement - Position 1 (Exhaust Gas Recirculation Valve Temperature Sensor Replacement - Position 1)
* Control Module References (Programming and Relearning) for ECM replacement, setup, and programming