Code P0168: Fuel Temperature Too High – Diagnosis and Solutions
Fault code P0168 is a generic powertrain code indicating that the powertrain control module (PCM) has detected an abnormally high fuel temperature via the dedicated sensor’s signal. If not addressed, this issue can affect engine performance and injection strategy, especially in flex-fuel vehicles.
Meaning of Code P0168
When code P0168 appears, the PCM has received a signal from the fuel temperature/composition sensor indicating that the fuel temperature exceeds the manufacturer’s predefined limits. This sensor, often integrated into the fuel line, analyzes both the composition (ethanol content, water presence) and the temperature of the fuel. It sends a complex electrical signal to the PCM in the form of a square wave, whose modulation (pulse width) varies with temperature. An excessively fast pulse width indicates an excessive temperature.
Symptoms of Code P0168
This code is often accompanied by few or no visible symptoms for the driver. However, one might sometimes observe:
- Illumination of the Malfunction Indicator Lamp (MIL) on the dashboard.
- Presence of other codes related to fuel composition.
- Eventually, a possible decrease in engine performance.
Possible Causes of Code P0168
Several elements can be the source of this fault:
- Faulty fuel temperature/composition sensor (most common cause).
- Faulty wiring or connectors (short circuit, open circuit, corrosion).
- Malfunction of an auxiliary temperature sensor (ambient air, intake air).
- Programming issue or internal PCM failure.
- Abnormal external heat source near the tank or fuel lines (e.g., exhaust).
How to Diagnose Code P0168?
Diagnosis requires some specialized tools: an OBD2 scanner, a digital multimeter (DVOM), an oscilloscope, and possibly an infrared thermometer.
- Check Technical Service Bulletins (TSBs): First, consult your manufacturer’s TSBs to see if the problem is subject to a recall or specific procedure.
- Visual Inspection: Carefully inspect the wiring and connectors associated with the sensor to identify any potential damage, burns, or corrosion.
- Electrical Test: Using the multimeter, check for the presence of the reference voltage (usually 5V) and ground at the sensor connector. Its absence may indicate a wiring or PCM problem.
- Sensor Test: With the oscilloscope, observe the live signal from the sensor. Compare the temperature read by the oscilloscope with a physical measurement of the fuel temperature using the infrared thermometer. A significant discrepancy confirms sensor failure.
- Contextual Check: If the actual temperature is indeed too high, look for an abnormal external heat source near the tank or fuel lines.
Solutions to Fix Code P0168
The repair depends on the identified root cause:
- Replace the sensor: If the sensor is faulty, replacing it is the solution.
- Repair the wiring: Repair or replace any damaged or corroded cables.
- Clean the connectors: Ensure connections are clean and secure.
- Update the PCM: In rare cases, a PCM software update may be necessary.
⚠️ Safety Tip: Always work on the fuel system in a well-ventilated area, with a cold engine, and following fuel circuit depressurization procedures.
Conclusion
Code P0168, although often without immediate symptoms, should not be ignored as it can disrupt the air-fuel mixture. A methodical diagnosis with the right tools is essential to identify and resolve the cause effectively, whether it’s a simple sensor or a wiring problem.
Need help diagnosing this code? Consult a professional mechanic or use our support forum to share your scanner data and get targeted advice for your vehicle model.