P0168

DTC P0168

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* 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 113°C (235°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.

Conditions for Clearing the DTC

DTC P0168 is a Type C DTC.

The message center displays Reduced Engine Power.

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.

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 (EGR Temperature Sensors) Temperature Versus Resistance (Fuel Temperature Sensor) Temperature Versus Resistance (IAT Sensor 1) Temperature Versus Resistance (ECT Sensors) Temperature Versus Resistance (IAT Sensor 2) Temperature Versus Resistance (EGT Sensors).

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

Repair Instructions

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

Fuel Temperature Sensor Replacement