14-01-2025
16 min.
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P2028 Evaporative Emissions (EVAP) Fuel Vapor Temperature Sensor Circuit Intermittent

P2028 Evaporative Emissions (EVAP) Fuel Vapor Temperature Sensor Circuit Intermittent is a generic OBD-II diagnostic trouble code indicating that the vehicle's control module has detected an intermittent electrical signal or connection problem in the EVAP fuel vapor temperature sensor circuit.

The EVAP system prevents gasoline vapors from escaping from the fuel tank and fuel system into the atmosphere. The fuel vapor temperature sensor provides the control module with information about the temperature of fuel vapors within the EVAP system.

In simple terms, the vehicle's computer is receiving an EVAP fuel vapor temperature sensor signal that becomes abnormal, unstable, or temporarily disappears.

The word "intermittent" is especially important. It means the problem may not be present continuously.

The sensor may work normally at one moment and then:

Lose its signal
Produce an unstable signal
Show an implausible temperature
Develop an electrical connection problem
Return to normal after vibration or temperature changes

Possible causes include:

Faulty EVAP fuel vapor temperature sensor
Damaged sensor wiring
Broken wire inside the insulation
Loose connector
Corroded terminals
Poor terminal tension
Water or moisture intrusion
Short circuit
Intermittent open circuit
Wiring chafing
Heat damage
Poor sensor ground
Reference or supply-voltage problem
EVAP harness damage
Faulty control module
Software or calibration problems

Because intermittent faults can disappear during testing, diagnosis should include a careful inspection of the wiring and connector while monitoring live sensor data.

What Does P2028 Mean?

The code description contains several important terms.

Evaporative Emissions (EVAP)

The EVAP system is designed to prevent fuel vapors from escaping into the atmosphere.

Gasoline naturally produces vapor, particularly when the fuel and fuel tank become warm.

Instead of allowing these vapors to escape, the EVAP system stores and manages them.

A typical EVAP system can include:

Fuel tank
Fuel filler neck
Fuel cap or capless filler system
EVAP charcoal canister
Purge valve
Vent valve
EVAP hoses
Pressure sensor
Temperature sensors on some applications
Leak-detection components
Control module

The exact system varies by vehicle.

Fuel Vapor Temperature Sensor

The fuel vapor temperature sensor measures the temperature associated with fuel vapor in the EVAP system.

The control module can use this information together with other EVAP data to evaluate vapor conditions and monitor the system.

Depending on the vehicle, the sensor may be integrated into an EVAP component rather than being a completely separate external sensor.

Its exact location is therefore vehicle-specific.

Circuit Intermittent

The word "intermittent" means the electrical problem occurs only sometimes.

This is different from a continuously failed circuit.

For example, a damaged wire may maintain electrical contact while the vehicle is stationary but lose contact when:

The engine vibrates
The vehicle drives over rough roads
The harness moves
Temperature changes occur
The connector expands or contracts
Moisture reaches the connector

This can make P2028 particularly difficult to diagnose.

A vehicle may be driven for several days without reproducing the problem, and then the code may return suddenly.

How Does the EVAP System Work?

A simplified EVAP system operates as follows.

1. Fuel vapors are produced

Fuel in the tank naturally produces vapor.

2. Vapors are contained

The fuel tank and EVAP system prevent the vapors from escaping directly into the atmosphere.

3. Vapors are stored

The charcoal canister absorbs and stores fuel vapors.

4. The control module manages vapor flow

Under appropriate operating conditions, the purge system allows stored vapor to enter the engine.

5. The engine burns the vapor

The fuel vapor becomes part of the engine's combustion process.

6. EVAP sensors monitor system conditions

Depending on the vehicle, sensors provide information about:

Pressure
Temperature
Flow
Leak conditions

An intermittent fuel-vapor temperature sensor signal can interfere with this monitoring process and trigger P2028.

Why Is EVAP Fuel Vapor Temperature Important?

Temperature affects fuel vapor behavior.

As fuel temperature increases, vapor generation can change.

The control module can use temperature information when evaluating EVAP system operation.

A reliable temperature signal helps the control system distinguish between normal and abnormal EVAP conditions.

If the sensor signal suddenly changes to an implausible value, disappears, or becomes unstable, the control module may determine that the sensor circuit is intermittent.

Symptoms of P2028

P2028 may produce few noticeable symptoms because the problem concerns an emissions-monitoring circuit.

Check Engine Light

The Check Engine Light is the most common symptom.

It may illuminate after the control module detects the intermittent fault during one or more drive cycles.

EVAP System Warning

Some vehicles may display an emissions-related warning message.

The exact warning depends on the manufacturer.

Fuel Vapor or Gasoline Smell

In some cases, an EVAP problem may be accompanied by a gasoline smell.

However, a fuel smell should not automatically be attributed to P2028.

A physical fuel or vapor leak must be inspected separately.

Difficult Fuel Filling

An EVAP problem elsewhere in the system can sometimes cause:

Fuel nozzle clicking off repeatedly
Slow refueling
Difficulty filling the fuel tank

However, these symptoms are not specific to P2028 and may be caused by a blocked vent or other EVAP problem.

Slightly Increased Emissions

If the EVAP system cannot properly control fuel vapors, evaporative emissions may increase.

Slight Fuel-Economy Changes

Fuel economy may change in some cases, particularly if the EVAP control system responds incorrectly.

However, P2028 does not necessarily cause a noticeable change in fuel consumption.

No Noticeable Driving Problems

This is common.

The vehicle may:

Start normally
Idle normally
Accelerate normally
Drive normally

while the Check Engine Light remains illuminated.

Common Causes of P2028

Faulty Fuel Vapor Temperature Sensor

The sensor itself may be failing intermittently.

Possible internal problems include:

Internal electrical failure
Intermittent resistance changes
Temperature-sensitive failure
Internal connection problems
Sensor degradation

The sensor may work correctly when cold and fail when hot, or vice versa.

Damaged Wiring

The wiring harness is one of the most important areas to inspect.

Possible problems include:

Broken wire
Partially broken conductor
Chafed insulation
Melted insulation
Corrosion
Wiring stretched too tightly
Previous improper repair

A wire can look intact from the outside while being broken internally.

Intermittent Open Circuit

An open circuit means electrical continuity is lost.

Because P2028 is intermittent, the connection may be restored when:

The harness moves
Vibration stops
Temperature changes
The connector is repositioned

This can make the fault difficult to reproduce.

Loose Connector

A connector that is not fully seated can cause the sensor signal to disappear intermittently.

Corroded Connector Terminals

Moisture and road contamination can cause corrosion.

Corroded terminals may create:

Increased resistance
Intermittent signal loss
Unstable voltage
Poor sensor operation

Poor Terminal Tension

A terminal may appear clean but fail to grip the mating pin correctly.

This can cause intermittent electrical contact.

Water or Moisture Intrusion

EVAP components are often located in areas exposed to:

Rain
Road spray
Mud
Snow
Salt

Moisture inside a connector can produce intermittent faults.

Wiring Chafing

The harness may rub against:

Body panels
Brackets
Fuel tank components
Exhaust components
Suspension components

Over time, insulation can wear through and expose the conductor.

Heat Damage

If the EVAP wiring is routed near hot exhaust components, excessive heat can damage the insulation or conductor.

Short Circuit

The sensor signal or supply circuit may intermittently contact:

Ground
Battery voltage
Another electrical circuit

This can cause the control module to detect an abnormal sensor signal.

Poor Ground

A weak or corroded ground connection can cause unstable sensor readings.

Reference or Supply-Voltage Problem

Depending on the sensor design, an unstable supply or reference voltage can affect sensor operation.

EVAP Component Problem

Although P2028 specifically identifies the fuel vapor temperature sensor circuit, other EVAP problems can sometimes be present at the same time.

Possible related problems include:

Damaged EVAP canister
Faulty purge valve
Faulty vent valve
Damaged EVAP hose
EVAP pressure problems
Fuel tank ventilation problems

These should be investigated if additional EVAP codes are present.

Fuel Tank or EVAP Pressure Problems

Abnormal pressure conditions can occur because of:

Blocked venting
Faulty valves
Damaged hoses
Canister problems

These conditions may not directly cause P2028 but can occur alongside it.

Control Module Problem

In rare cases, the control module may have an internal fault or an issue processing the sensor signal.

The control module should generally be considered only after the sensor and wiring have been thoroughly tested.

Software or Calibration Problem

Some vehicles may have software or calibration updates that affect EVAP sensor monitoring.

Vehicles Commonly Affected by P2028

P2028 can occur on vehicles equipped with an EVAP fuel vapor temperature sensor and the corresponding monitoring strategy.

Examples may include:

Ford Mustang
Ford F-150
Ford Explorer
Chevrolet Silverado
Chevrolet Tahoe
Chevrolet Suburban
GMC Sierra
GMC Yukon
Cadillac Escalade
Dodge Charger
Dodge Challenger
Jeep Grand Cherokee
Ram 1500
Toyota Tundra
Toyota Sequoia
Toyota Tacoma
Nissan Altima
Nissan Pathfinder
Nissan Armada
BMW 3 Series
BMW 5 Series
Mercedes-Benz C-Class
Mercedes-Benz E-Class
Volkswagen Passat
Audi A4

This list is not exhaustive.

The exact application of P2028 depends on the vehicle's EVAP system, engine, model year, and control-module configuration.

How Is P2028 Diagnosed?

P2028 can be more difficult to diagnose than a permanent circuit fault because the problem may disappear during inspection.

The key question is:

Is the fuel vapor temperature sensor failing intermittently, or is the electrical circuit intermittently losing its connection?

Step 1: Scan for Additional Trouble Codes

Use a suitable diagnostic scan tool to retrieve:

Stored codes
Pending codes
History codes
Manufacturer-specific codes

Look for additional EVAP-related faults.

Related codes can provide important clues.

Step 2: Review Freeze-Frame Data

Check the conditions under which P2028 was stored.

Look at:

Engine temperature
Intake-air temperature
Ambient temperature
Fuel level
Vehicle speed
Engine load
EVAP temperature
EVAP pressure where available
Battery voltage

If the fault occurs only at a particular temperature or operating condition, this information can be valuable.

Step 3: Monitor Live Sensor Data

Use a scan tool to monitor the fuel vapor temperature sensor.

Watch for:

Sudden temperature jumps
Implausibly high values
Implausibly low values
Signal dropouts
Frozen readings
Rapid fluctuations

The reading should change in a manner consistent with actual temperature conditions.

Step 4: Compare the Sensor With Other Temperature Sensors

Compare the EVAP fuel vapor temperature reading with available temperature information such as:

Ambient temperature
Fuel temperature where available
Intake-air temperature
Coolant temperature

The readings do not need to be identical because they measure different locations.

The purpose is to identify obviously implausible behavior.

Step 5: Inspect the Sensor

Inspect the fuel vapor temperature sensor for:

Physical damage
Corrosion
Contamination
Loose mounting
Damaged terminals
Signs of moisture intrusion

Step 6: Inspect the Connector

Check the connector carefully.

Look for:

Corrosion
Moisture
Bent pins
Loose pins
Damaged seals
Poor terminal tension
Broken locking tabs

A visual inspection alone may not reveal a terminal-tension problem.

Step 7: Perform a Wiggle Test

This is particularly useful for an intermittent code.

Monitor the sensor signal or circuit voltage while carefully moving:

Sensor connector
Sensor wiring
EVAP harness
Nearby connectors

If the signal suddenly changes when the harness moves, the wiring or connector is likely involved.

Step 8: Check Circuit Continuity

Test the wiring between the sensor and the control module.

Check for:

Open circuits
Excessive resistance
Poor connections
Intermittent continuity

A continuity test should be performed according to the manufacturer's diagnostic procedure.

Step 9: Check for Short Circuits

Test the circuit for unwanted contact with:

Ground
Battery voltage
Other circuits

Intermittent shorts may require moving the harness while monitoring the circuit.

Step 10: Check Sensor Resistance

If the sensor is a resistance-based temperature sensor, measure its resistance according to manufacturer specifications.

Compare the measured resistance with the expected value for the actual sensor temperature.

Do not rely on a generic resistance-temperature chart unless it applies specifically to that sensor.

Step 11: Check Sensor Supply and Ground

Verify the applicable:

Supply voltage
Reference voltage
Ground
Signal circuit

The exact circuit design differs by manufacturer.

Step 12: Test During Temperature Changes

Because some intermittent sensor failures are temperature-dependent, monitor the signal as the sensor temperature changes.

A sensor may operate correctly when cold but become unstable when heated.

Step 13: Inspect the EVAP Harness Routing

Follow the wiring physically.

Check areas near:

Fuel tank
EVAP canister
Exhaust
Rear suspension
Fuel lines
Body brackets

Look for rubbing, stretching, heat damage, and previous repairs.

Step 14: Check EVAP System Components

If additional EVAP codes are present, inspect:

Purge valve
Vent valve
Charcoal canister
EVAP hoses
Fuel tank connections
Pressure sensor
Leak-detection components

Step 15: Check for EVAP Leaks

If other EVAP codes are present, perform the manufacturer's recommended leak test.

A smoke test may be used where appropriate to locate physical leaks.

A leak does not automatically prove that the fuel vapor temperature sensor circuit is defective.

Step 16: Check Fuel Level

Verify fuel level when evaluating EVAP faults.

EVAP diagnostic tests can be affected by fuel level and operating conditions.

Step 17: Check Control Module Data

If the sensor and wiring test correctly, verify that the control module is correctly receiving and interpreting the signal.

Step 18: Check Manufacturer Technical Information

Look for:

Technical Service Bulletins
Known sensor failures
Wiring harness issues
Connector problems
Sensor revisions
Software updates
EVAP diagnostic procedures

Step 19: Reproduce the Intermittent Fault

If possible, reproduce the conditions under which the code originally appeared.

This may involve:

Road testing
Temperature changes
Harness movement
Vibration
EVAP system operation

The goal is to observe the exact moment the sensor signal becomes abnormal.

Step 20: Perform a Complete EVAP Verification

After repairs, verify:

Fuel vapor temperature signal
Sensor circuit integrity
EVAP pressure where applicable
Purge operation
Vent operation
EVAP leak status
Readiness monitor status

How to Fix P2028

The correct repair depends on whether the intermittent problem is caused by the sensor, wiring, connector, or control system.

Replace the Fuel Vapor Temperature Sensor

If testing confirms that the sensor itself is intermittently failing, replace it with the correct vehicle-specific component.

Repair Damaged Wiring

Repair or replace wiring affected by:

Chafing
Heat
Vibration
Corrosion
Stretching
Previous improper repairs

Secure the harness correctly after repair.

Repair an Intermittent Open Circuit

If the circuit loses continuity intermittently, repair:

Broken conductors
Damaged splices
Loose terminals
Connector problems

Repair Short Circuits

If the sensor circuit intermittently contacts ground, battery voltage, or another circuit, locate and repair the wiring fault.

Repair or Replace the Connector

If the connector has:

Corrosion
Moisture
Loose terminals
Bent pins
Damaged seals
Poor terminal tension

repair or replace it as required.

Correct Sensor Supply or Ground Problems

Repair faults involving:

Reference voltage
Supply voltage
Ground
Related wiring

Repair EVAP Components Where Necessary

If additional EVAP faults are found, repair the affected:

Purge valve
Vent valve
Charcoal canister
EVAP hoses
Pressure sensor
Leak-detection components

Do not replace unrelated EVAP parts solely because P2028 is present.

Repair Control Module Problems

If the control module is confirmed to have an internal fault after the sensor and circuit have been verified, it may require repair, replacement, or programming.

Update Control Module Software

If the manufacturer has released a software update addressing EVAP sensor monitoring, apply the appropriate update.

Clear the Code and Verify the Repair

After completing the repair:

Clear P2028.
Start the vehicle and monitor the fuel vapor temperature signal.
Check the sensor circuit for stable operation.
Perform a wiggle test if appropriate.
Drive the vehicle through the conditions associated with the original fault.
Verify EVAP system operation.
Check EVAP pressure data where applicable.
Confirm that no additional EVAP codes return.
Complete the required drive cycle.
Rescan for stored and pending trouble codes.

The repair should be considered successful only when the sensor signal remains stable and P2028 does not return.

What Happens If P2028 Is Ignored?

Because P2028 is primarily an EVAP sensor-circuit fault, the vehicle may continue to drive normally.

However, an unresolved problem can affect:

EVAP system monitoring
Emissions diagnostics
Fuel-vapor control
EVAP readiness testing
Check Engine Light status

If the underlying problem involves an actual EVAP leak or fuel-vapor issue, emissions can increase.

Can You Drive With P2028?

In most cases, a vehicle with P2028 can still be driven if it starts and operates normally.

The fault is usually associated with an emissions-monitoring circuit rather than a system required for basic engine operation.

However, the problem should still be diagnosed.

Pay particular attention if the vehicle also has:

Strong gasoline smell
Fuel leakage
Difficult refueling
Multiple EVAP codes
Rough running
Starting problems
Additional Check Engine Light codes

A strong fuel smell or visible fuel leak should be investigated promptly rather than assuming it is caused only by the sensor circuit.

Is P2028 a Serious Code?

P2028 is generally considered a low-to-moderate severity diagnostic trouble code.

It normally does not cause immediate engine failure.

However, ignoring the fault can leave an EVAP monitoring problem unresolved and may prevent the vehicle from completing emissions-related diagnostic monitors.

The severity is higher if P2028 occurs together with:

Fuel leaks
EVAP system pressure problems
Large EVAP leaks
Multiple emissions faults
Fuel-system problems

Therefore, the code should be diagnosed even if the vehicle appears to drive normally.

P2028 vs. P2029 and P2030

P2028 belongs to a different system from the fuel-fired heater codes that follow it.

Code	General Meaning
P2028	EVAP Fuel Vapor Temperature Sensor Circuit Intermittent
P2029	Fuel-Fired Heater Disabled Malfunction
P2030	Fuel-Fired Heater Performance Malfunction

The distinction is important.

P2028 → EVAP fuel vapor temperature sensor circuit

P2029 → Fuel-fired heater disabled condition

P2030 → Fuel-fired heater performance problem

Therefore, P2028 should not automatically be diagnosed as a fuel-fired heater problem.

P2028 vs. Other EVAP Codes

P2028 is specifically related to the fuel vapor temperature sensor circuit.

Other EVAP codes can concern:

Purge flow
Vent valve operation
EVAP leaks
Pressure sensor
Fuel tank pressure
Vapor-system performance

An important distinction is that P2028 describes an intermittent sensor-circuit problem, not necessarily an EVAP leak.

A vehicle can have an EVAP leak without P2028, and P2028 can occur without a physical EVAP leak.

P2028 vs. a Permanent Circuit Fault

The intermittent nature of P2028 is important during diagnosis.

A permanent electrical fault may produce a sensor signal that is consistently:

Too high
Too low
Missing

An intermittent fault may appear only when:

The harness vibrates
The vehicle drives over rough roads
Temperature changes
Moisture reaches a connector
A connector moves
A damaged conductor separates

This is why a simple static resistance or continuity check may not always identify the problem.

A wiggle test combined with live-data monitoring can be particularly useful when performed according to the manufacturer's diagnostic procedure.

How to Prevent P2028

Not every sensor or wiring failure can be prevented, but proper maintenance can reduce the risk.

Recommended practices include:

Inspect EVAP wiring during routine service.
Keep wiring secured away from exhaust heat.
Repair damaged wiring promptly.
Check EVAP connectors for corrosion.
Protect connectors from moisture intrusion.
Avoid damaging EVAP components during underbody repairs.
Inspect EVAP hoses for cracks and deterioration.
Use the correct replacement sensor.
Install connectors fully and securely.
Address gasoline smells promptly.
Repair fuel-vapor leaks quickly.
Do not ignore Check Engine Light warnings.
Maintain the fuel system according to manufacturer recommendations.
Inspect wiring after fuel-tank or exhaust-system work.

Final Thoughts

P2028 Evaporative Emissions (EVAP) Fuel Vapor Temperature Sensor Circuit Intermittent indicates that the vehicle's control module has detected an intermittent problem in the electrical circuit associated with the EVAP fuel vapor temperature sensor.

The key word is "intermittent."

The sensor may work normally most of the time but occasionally produce an abnormal signal or lose electrical contact.

Common causes include:

Faulty fuel vapor temperature sensor
Broken or damaged wiring
Intermittent open circuit
Short circuit
Loose connector
Corroded terminals
Poor terminal tension
Moisture intrusion
Wiring chafing
Heat damage
Poor ground
Reference or supply-voltage problems
EVAP harness damage
Control-module problems
Software or calibration issues

The correct diagnostic approach is to monitor the sensor's live data while carefully inspecting the complete electrical circuit.

A technician should check for additional codes, review freeze-frame data, inspect the sensor and connector, perform a wiggle test, verify supply and ground circuits, test continuity, check for shorts, and compare the sensor's behavior with actual temperature conditions.

If the sensor itself is confirmed to be faulty, replacement may correct the problem. If the signal is being lost because of wiring or connector damage, repairing the circuit is the appropriate solution.

An EVAP leak should not automatically be assumed simply because P2028 is stored.

Likewise, the fuel vapor temperature sensor should not automatically be replaced without testing.

In most cases, P2028 does not prevent the vehicle from being driven normally. However, it can interfere with EVAP emissions monitoring and may prevent emissions-related diagnostic monitors from completing.

Once the underlying fault has been repaired, the code should be cleared and the vehicle should be driven through the appropriate operating conditions to verify that the sensor signal remains stable and P2028 does not return.

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