P0168

DTC P0168

Diagnostic Instructions

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

DTC Descriptor
DTC P0168
- Engine Fuel Over-Temperature

Circuit/System Description

Fuel is drawn from the fuel tank through the fuel heater, then to the fuel injection pump. Fuel temperature is monitored by the fuel temperature sensor, which is located in the fuel return line on the engine. The engine control module (ECM) supplies 5 volts and a ground circuit to the sensor. When the ECM detects a fuel temperature above the pre-determined value, this diagnostic will fail, but will not turn the malfunction indicator lamp (MIL) ON.

Conditions for Running the DTC

* The ignition is ON.
* DTC P0168 runs continuously within the enabling conditions.

Conditions for Setting the DTC

* The fuel temperature sensor is above 115°C (239°F) for more than 10 seconds.
* DTC P0181, P0182 or P0183 are not set.

Action Taken When the DTC Sets

* DTC P0168 is a Type C DTC.
* The message center displays Reduced Engine Power.

Conditions for Clearing the DTC

DTC P0168 is a Type C DTC.

Reference Information
Schematic Reference

Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector End Views By Name)
Electrical Information Reference

* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)

DTC Type Reference

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

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

Circuit/System Verification

The Fuel Temperature and ECT Temperature parameters should closely match each other when the engine has not been started and soaked overnight.

Circuit/System Testing

Important: Fuel temperature overheating may be cause by a fuel heater element that is stuck on. Refer to Fuel Heater Always On (Fuel Heater Always On).


With ignition ON and the engine OFF, observe the Fuel Temperature and ECT Temperature parameters with a scan tool.

If the temperatures do not closely match each other when the engine has cold soaked overnight, test for a skewed fuel temperature sensor. Refer to Component Testing in this diagnostic.

Component Testing

1. Remove the fuel temperature sensor from the engine.
2. Measure the resistance of the sensor at different ambient temperatures and record results. Compare the results to the Temperatures vs. Resistance Fuel Temperature table. Refer to Temperature Versus Resistance (Fuel Temperature Sensor) (Temperature Versus Resistance (Fuel Temperature Sensor)) Temperature Versus Resistance (ECT Sensors) (Temperature Versus Resistance (ECT Sensors)) Temperature Versus Resistance (IAT Sensor 1) (Temperature Versus Resistance (IAT Sensor 1)) Temperature Versus Resistance (IAT Sensor 2) (Temperature Versus Resistance (IAT Sensor 2)) Temperature Versus Resistance (EGT Sensors) (Temperature Versus Resistance (EGT Sensors)) Temperature Versus Resistance (EGR Temperature Sensors) (Temperature Versus Resistance (EGR Temperature Sensors)).

• If the fuel temperature sensor is skewed, replace the sensor.

Repair Instructions

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

Fuel Temperature Sensor Replacement (Service and Repair)