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P0168 Code Explained: Fuel Temperature Too High Causes, Symptoms & Fixes

P0168 code illustration showing an overheating fuel rail, fuel temperature sensor, high-temperature warning, Check Engine Light, Pro Street TV logo, and www.ProStreetOnline.com.

If your OBD-II scanner displays P0168, your vehicle’s Engine Control Module (ECM) or Powertrain Control Module (PCM) has detected that the fuel temperature has exceeded the maximum limit programmed by the manufacturer.

The generic OBD-II definition for P0168 is:

Fuel Temperature Too High

Unlike oxygen sensor-related trouble codes, P0168 is associated with the fuel delivery and engine management system. The PCM relies on the fuel temperature sensor to monitor fuel temperature so it can adjust fuel delivery, injection timing, vapor management, and emissions controls.

Fuel temperature becomes especially important on:

When fuel becomes hotter than expected, its density changes, vapor formation increases, and fuel system performance may suffer. If the PCM detects a fuel temperature above the manufacturer’s allowable range, it stores P0168 and usually illuminates the Check Engine Light.

Common causes include:

Unlike P0180 through P0184, which indicate electrical faults in the fuel temperature sensor circuit, P0168 specifically indicates that the PCM believes the fuel itself is excessively hot.

What Does the P0168 Code Mean?

Modern vehicles continuously monitor fuel temperature to ensure accurate fuel delivery and emissions control.

As fuel temperature rises:

The PCM uses information from the fuel temperature sensor to compensate for these changes.

When fuel temperature exceeds manufacturer specifications, the PCM stores P0168.

The code does not automatically mean the fuel temperature sensor has failed.

The PCM may be accurately reporting genuinely excessive fuel temperatures.

How the Fuel Temperature Sensor Works

Most vehicles use a thermistor-type fuel temperature sensor.

A thermistor changes electrical resistance as temperature changes.

Generally:

The PCM supplies:

As fuel temperature changes, the sensor alters the return voltage, allowing the PCM to calculate fuel temperature.

Why Fuel Temperature Matters

Fuel temperature affects several important engine functions.

The PCM uses fuel temperature information for:

Keeping fuel within the proper operating range helps maintain engine performance and emissions compliance.

Where Is the Fuel Temperature Sensor Located?

Fuel temperature sensor location varies by manufacturer.

Common locations include:

Always consult the factory service manual for the exact sensor location on your vehicle.

How the PCM Detects P0168

The PCM continuously monitors:

If the reported fuel temperature exceeds the manufacturer’s calibrated limit for a specified amount of time, the PCM stores P0168.

Some manufacturers require multiple drive cycles before permanently illuminating the Check Engine Light.

Can High Fuel Temperature Cause Problems?

Yes.

Excessively hot fuel may contribute to:

Modern returnless fuel systems are especially sensitive because fuel remains in the engine compartment longer than older return-style systems.

Can a Bad Fuel Temperature Sensor Cause P0168?

Absolutely.

A faulty sensor may incorrectly report excessively high fuel temperatures even when the fuel is operating normally.

Typical sensor failures include:

Sensor testing should always be performed before replacing expensive fuel system components.

Can Engine Heat Cause P0168?

Yes.

High engine compartment temperatures are one of the most common contributors to P0168.

Possible causes include:

Under extreme conditions, fuel temperature can legitimately exceed normal operating limits.

P0168 Quick Facts

ItemInformation
DTCP0168
Generic DefinitionFuel Temperature Too High
SystemFuel & Engine Management
SeverityModerate
Safe to Drive?Usually, with caution
Common SymptomsCheck Engine Light, hard hot starts, hesitation, reduced performance
Common CausesFailed fuel temperature sensor, excessive engine heat, wiring faults, restricted fuel system
Typical Repair Cost$100–900+
Related CodesP0180, P0181, P0182, P0183, P0184

Common Vehicles That Experience P0168

P0168 may appear on vehicles from:

The code is especially common on vehicles equipped with direct fuel injection (GDI), common-rail diesel injection, or flex-fuel systems that actively monitor fuel temperature.

What Does P0168 Really Mean?

The wording of P0168 often leads drivers to believe the engine is overheating.

The code does not automatically mean:

Instead, it means the PCM has determined that fuel temperature is higher than expected, either because the fuel is genuinely overheating or because the fuel temperature sensor or its circuit is providing inaccurate information.

The fault may involve:

Think of P0168 as the PCM saying:

“The fuel in the system appears hotter than it should be. I need the fuel temperature sensor, wiring, cooling system, and fuel system inspected to determine whether the temperature is truly excessive or the sensor is reporting incorrect data.”

Common P0168 Scan Tool Patterns

Monitoring live scan-tool data is one of the fastest ways to diagnose P0168.

Unlike fuel temperature sensor circuit codes such as P0180 through P0184, P0168 indicates the PCM believes the actual fuel temperature has exceeded the manufacturer’s acceptable operating range.

Professional scan tools allow technicians to compare fuel temperature with coolant temperature, intake air temperature, ambient temperature, fuel pressure, and engine operating conditions to determine whether the problem is caused by actual fuel overheating or a faulty sensor.

Pattern 1: Fuel Temperature Much Higher Than Ambient Temperature

The most common scan-tool pattern is:

Possible causes include:

Pattern 2: Fuel Temperature Increases After Hot Soak

Some vehicles only store P0168:

Possible causes include:

Pattern 3: Fuel Temperature Does Not Match Other Sensors

Compare:

If:

The fault may involve:

Comparing multiple temperature sensors helps identify sensor faults.

Pattern 4: Fuel Temperature Rises With Engine Load

During acceleration or towing:

Possible causes include:

Pattern 5: Fuel Temperature Remains Fixed

Some scan tools show:

Possible causes include:

A healthy sensor should display gradual temperature changes.

Pattern 6: Fuel Temperature High With No Other Fuel System Codes

Some vehicles store only:

without:

This usually indicates:

Common Symptoms of P0168

The severity of symptoms depends on whether fuel temperature is actually excessive or the sensor is reporting inaccurate information.

Common symptoms include:

Some vehicles exhibit no noticeable drivability symptoms beyond the Check Engine Light.

Check Engine Light

The Check Engine Light is usually the first symptom.

Most manufacturers require:

before storing P0168.

Hard Hot Starts

Excessively hot fuel can increase vapor formation.

This may result in:

These symptoms are more common in extremely hot climates.

Reduced Engine Performance

In some vehicles, the PCM may adjust fuel delivery when excessive fuel temperature is detected.

Possible symptoms include:

Most vehicles experience only mild performance changes.

Reduced Fuel Economy

Higher fuel temperatures may slightly reduce:

Fuel economy changes are usually minor.

Is P0168 Serious?

P0168 is generally considered a moderate severity diagnostic trouble code.

The vehicle is usually safe to drive.

However, prolonged operation with excessively high fuel temperatures may contribute to:

Repairs should be completed promptly.

Can You Drive With P0168?

Usually, yes.

Driving is generally safe if:

Repairs should be scheduled immediately if:

P0168 vs Related Trouble Codes

Understanding related fuel temperature codes simplifies diagnosis.

P0168

Fuel Temperature Too High

The PCM detects fuel temperature exceeding manufacturer specifications.

P0180

Fuel Temperature Sensor “A” Circuit Malfunction

General electrical problem affecting the fuel temperature sensor circuit.

P0181

Fuel Temperature Sensor “A” Range/Performance

The sensor operates outside expected performance limits.

P0182

Fuel Temperature Sensor “A” Circuit Low Input

The PCM receives a lower-than-expected voltage signal.

P0183

Fuel Temperature Sensor “A” Circuit High Input

The PCM receives a higher-than-expected voltage signal.

P0184

Fuel Temperature Sensor “A” Circuit Intermittent

The fuel temperature sensor signal becomes intermittent or unstable.

30 Common Causes of P0168

The most common causes include:

  1. Failed fuel temperature sensor
  2. Fuel temperature sensor drift
  3. Engine compartment heat soak
  4. Engine overheating
  5. Cooling fan failure
  6. Low coolant level
  7. Restricted radiator airflow
  8. Missing heat shields
  9. Turbocharger heat transfer
  10. Exhaust heat affecting fuel lines
  11. Restricted fuel return system
  12. High-pressure fuel pump problems
  13. Fuel rail overheating
  14. Faulty fuel pressure regulator
  15. Damaged sensor wiring
  16. Connector corrosion
  17. Loose electrical connector
  18. Open circuit
  19. Short circuit
  20. Poor ground connection
  21. High circuit resistance
  22. Low battery voltage
  23. Charging system problems
  24. Contaminated fuel
  25. Low fuel level causing excess heat
  26. Faulty fuel composition sensor (flex-fuel vehicles)
  27. PCM software issue
  28. Internal PCM fault
  29. Low-quality aftermarket sensor
  30. PCM failure (rare)

Final Thoughts

The P0168 Fuel Temperature Too High code indicates the PCM has detected that fuel temperature has exceeded the manufacturer’s expected operating range. While actual fuel overheating is possible, a faulty fuel temperature sensor, damaged wiring, cooling system problems, heat soak, restricted fuel flow, or electrical faults are often responsible.

Proper diagnosis should determine whether the fault originates in:

The next section of this guide covers:

Following a structured diagnostic process prevents unnecessary parts replacement while restoring accurate fuel temperature monitoring and proper engine performance.

Related Pro Street Diagnostic Guides

How to Diagnose the P0168 Code

Diagnosing P0168 requires determining whether the fuel is actually overheating or whether the fuel temperature sensor is reporting incorrect information.

Unlike P0180 through P0184, which indicate electrical faults or performance issues within the fuel temperature sensor circuit, P0168 indicates the PCM believes the measured fuel temperature itself is excessively high.

The condition may be caused by:

Proper diagnosis should determine whether the problem originates in the fuel temperature sensor, fuel delivery system, cooling system, wiring, or PCM before replacing expensive components.

Safety Precautions

Before beginning diagnosis:

Modern gasoline direct-injection and common-rail diesel systems may operate at thousands of PSI, making proper safety procedures critical.

Tools Required

Professional diagnosis may require:

An infrared thermometer is useful for comparing actual fuel rail temperatures with scan-tool readings.

Step 1 – Verify the Code

Connect a professional scan tool.

Record:

Monitor:

Always save freeze-frame information before clearing any diagnostic trouble codes.

Step 2 – Check for Related Trouble Codes

P0168 commonly appears with:

Related codes often simplify diagnosis.

Code CombinationLikely Diagnosis
P0168 onlyActual high fuel temperature or sensor error
P0168 + P0180Fuel temperature sensor circuit fault
P0168 + P0181Sensor performance problem
P0168 + P0217Engine overheating affecting fuel temperature
P0168 + P0087Fuel delivery concern

Repair related faults before replacing expensive fuel system components.

Step 3 – Monitor Live Fuel Temperature Data

Allow the engine to reach operating temperature.

Observe:

Normal operation:

Abnormal operation:

Large differences between scan data and actual temperatures indicate additional testing is needed.

Step 4 – Compare Fuel Temperature to Actual Temperature

Using an infrared thermometer:

Measure:

Compare those readings with the scan tool.

If scan-tool data differs significantly from measured temperatures, suspect:

Step 5 – Inspect the Fuel Temperature Sensor

Inspect the sensor for:

A damaged sensor can falsely report excessively high fuel temperatures.

Step 6 – Inspect the Electrical Connector

Disconnect the sensor connector.

Inspect for:

Poor electrical connections frequently distort sensor readings.

Step 7 – Inspect the Wiring Harness

Inspect wiring between the sensor and PCM.

Look for:

Heat damage is especially common near turbochargers and exhaust manifolds.

Step 8 – Test Sensor Voltage

Using a digital multimeter:

Verify:

Compare measured values with manufacturer specifications.

Incorrect voltage readings may indicate wiring or PCM faults.

Step 9 – Test Sensor Resistance

Disconnect the fuel temperature sensor.

Measure resistance.

Compare resistance at known temperatures using the manufacturer’s resistance chart.

If resistance does not change appropriately with temperature, replace the sensor.

Step 10 – Inspect the Cooling System

Since excessive engine heat can raise fuel temperature:

Inspect:

Correct cooling system problems before replacing fuel system components.

Step 11 – Inspect for Fuel Heat Soak

Inspect for:

Excessive heat soak can legitimately raise fuel temperature after shutdown or extended idling.

Step 12 – Inspect the Fuel Delivery System

Inspect:

Restricted fuel circulation can increase fuel temperature.

Step 13 – Review Technical Service Bulletins

Before replacing expensive components:

Review manufacturer Technical Service Bulletins (TSBs).

Look for updates involving:

Some manufacturers have released updated calibrations for false P0168 detection.

Step 14 – Review Freeze-Frame Data

Compare current operating conditions with freeze-frame information.

Review:

Freeze-frame data often identifies exactly when excessive fuel temperature occurred.

Step 15 – Inspect PCM Connector Integrity

Inspect PCM connectors for:

Poor PCM connections may distort fuel temperature sensor readings.

Step 16 – Verify Charging System Voltage

Measure charging voltage.

Normal charging voltage should remain between:

Electrical system problems can interfere with accurate sensor operation.

Step 17 – Inspect Previous Repairs

Inspect for:

Improper repairs frequently create inaccurate sensor readings.

Step 18 – Verify Fuel Pressure

Measure fuel pressure using the proper procedure.

Compare readings with manufacturer specifications.

Fuel pressure abnormalities may contribute to excessive fuel temperatures.

Step 19 – Verify Sensor Operation During Road Test

Monitor live data while driving.

Observe:

Fuel temperature should rise gradually without sudden spikes or unrealistic values.

Step 20 – Confirm the Diagnosis

Before replacing any major component, verify:

Completing these diagnostic steps prevents unnecessary parts replacement while accurately identifying the root cause of P0168.

Step 21 – Replace the Fuel Temperature Sensor

If testing confirms the fuel temperature sensor is reporting incorrect values or has failed internally, replacement is the proper repair.

General replacement procedure:

  1. Relieve fuel system pressure according to the manufacturer’s procedure.
  2. Disconnect the negative battery cable.
  3. Disconnect the electrical connector from the sensor.
  4. Remove the sensor from the fuel rail, fuel line, fuel pump module, or fuel composition sensor assembly (depending on vehicle design).
  5. Inspect the sealing surfaces and O-rings.
  6. Install an OEM or high-quality replacement sensor.
  7. Reconnect the electrical connector.
  8. Restore fuel system pressure.
  9. Clear all diagnostic trouble codes.
  10. Verify proper sensor operation using a professional scan tool.

OEM sensors generally provide more accurate temperature readings and longer service life than low-cost aftermarket replacements.

Step 22 – Repair Damaged Wiring

Inspect the complete fuel temperature sensor wiring harness.

Repair:

Heat from the engine, turbocharger, or exhaust system frequently damages nearby wiring.

Step 23 – Repair Connector Problems

Inspect the fuel temperature sensor connector.

Repair or replace:

Poor electrical connections can cause inaccurate fuel temperature readings.

Step 24 – Repair Ground Circuit Problems

Inspect:

Measure:

Poor grounds may distort sensor voltage and cause false high-temperature readings.

Step 25 – Repair Cooling System Problems

If excessive engine heat is contributing to high fuel temperatures, inspect and repair:

Correcting engine overheating often eliminates P0168.

Step 26 – Repair Fuel System Heat Soak Problems

Inspect for:

Installing missing heat shields or repairing damaged insulation may significantly reduce fuel temperatures.

Step 27 – Repair Fuel Delivery Problems

Inspect the complete fuel system.

Repair:

Restricted fuel circulation can increase fuel temperature under heavy load.

Step 28 – Update PCM Software

Before replacing the PCM:

Review manufacturer Technical Service Bulletins (TSBs).

Manufacturers occasionally release software updates addressing:

Always verify the PCM contains the latest available calibration.

Step 29 – Verify Fuel Temperature Operation

After repairs:

Monitor:

Verify:

Complete a full drive cycle to confirm the repair.

Step 30 – Consider PCM Failure

PCM failure is extremely uncommon.

Only suspect the PCM after confirming:

PCM replacement should always be the final diagnostic step.

How to Fix P0168

The proper repair depends entirely on the diagnostic results.

Common repairs include:

Verifying the Repair

After completing repairs:

  1. Clear all diagnostic trouble codes.
  2. Start the engine.
  3. Allow the engine to reach operating temperature.
  4. Monitor live fuel temperature data.
  5. Compare fuel temperature with coolant and intake air temperatures.
  6. Complete a full drive cycle.
  7. Confirm no pending or permanent DTCs return.
  8. Perform a final scan to verify a successful repair.

A successful repair restores accurate fuel temperature monitoring, proper fuel system operation, normal emissions performance, and prevents the P0168 code from returning.

Typical Repair Costs

RepairTypical Cost
Professional diagnosis$100–250
Fuel temperature sensor replacement$150–450
Wiring repair$100–400
Connector replacement$100–300
Ground circuit repair$100–250
Cooling system repair$150–1,500+
Fuel pump replacement$400–1,500
Fuel pressure regulator replacement$200–700
Fuel filter replacement$100–300
Heat shield replacement$100–500
PCM software update$100–250
PCM replacement$800–2,000+

Repair costs vary depending on vehicle design, labor rates, fuel system configuration, and the underlying cause of the excessive fuel temperature.

Common Diagnostic Mistakes

Avoid these common mistakes:

Many P0168 repairs involve correcting cooling system problems or sensor issues rather than replacing major fuel system components.

Manufacturer-Specific Notes

Ford

Inspect:

Heat soak is a common contributor to P0168 on EcoBoost applications.

General Motors (Chevrolet/GMC)

Verify:

Direct-injection engines are particularly sensitive to fuel temperature changes.

Toyota/Lexus

Inspect:

Factory scan tools provide enhanced fuel temperature diagnostics.

Honda/Acura

Inspect:

Engine compartment heat can affect sensor readings on turbocharged models.

Nissan/Infiniti

Verify:

Turbocharged engines may experience higher fuel temperatures during prolonged idle periods.

BMW/Mercedes-Benz

Inspect:

Factory diagnostic software provides advanced fuel system temperature analysis.

Hyundai/Kia

Inspect:

Electrical connection problems are common causes of inaccurate fuel temperature readings.

Frequently Asked Questions

What usually fixes P0168?

The most common repairs include replacing the fuel temperature sensor, repairing damaged wiring, correcting cooling system problems, restoring proper fuel circulation, replacing damaged connectors, repairing poor grounds, or updating PCM software.

Can I drive with P0168?

Usually, yes. Most vehicles remain drivable, but repairs should be completed promptly because excessive fuel temperature can reduce performance, increase emissions, and contribute to hard hot starts.

Does P0168 always mean the fuel is actually overheating?

No. A faulty fuel temperature sensor, damaged wiring, connector corrosion, or sensor calibration errors can falsely report excessively high fuel temperatures.

Can engine overheating cause P0168?

Yes. An overheating engine can significantly increase fuel temperature, especially on direct-injection and turbocharged engines where the fuel rail is exposed to high engine compartment temperatures.

Can P0168 cause a failed emissions inspection?

Yes. If the Check Engine Light is illuminated, the vehicle will typically fail an OBD-II emissions inspection until the underlying fault is repaired.

Is P0168 a serious code?

P0168 is generally considered a moderate severity diagnostic trouble code. While it may not immediately affect drivability, prolonged operation with excessive fuel temperatures or inaccurate sensor readings can reduce engine performance, increase emissions, and contribute to fuel system wear.

Final Thoughts

The P0168 Fuel Temperature Too High code indicates the PCM has detected fuel temperatures exceeding the manufacturer’s expected operating range. While actual fuel overheating can occur, faulty fuel temperature sensors, damaged wiring, cooling system problems, heat soak, restricted fuel flow, and electrical faults are often responsible.

A complete diagnosis should always verify:

Following a structured diagnostic process prevents unnecessary parts replacement while restoring accurate fuel temperature monitoring, proper fuel delivery, emissions compliance, and reliable engine operation.

Continue Your Pro Street Fuel System Series

Related guides include:

These guides provide comprehensive coverage of fuel temperature monitoring, cooling system diagnostics, fuel system troubleshooting, and advanced OBD-II repair procedures.

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