EVAP Fuel Vapor Temperature Sensor Circuit Intermittent
Diagnostic Trouble Code P2028 indicates that the Powertrain Control Module (PCM) has detected an intermittent voltage signal from the Evaporative Emissions (EVAP) fuel vapor temperature sensor circuit. The PCM sets this code when the sensor's signal fluctuates erratically or drops out intermittently, falling outside the expected operating parameters.
This code primarily affects the vehicle's emissions system and will not cause drivability issues or strand you. However, it should be diagnosed and repaired to ensure the EVAP system functions correctly and to pass emissions testing.
Common symptoms
- Illuminated Check Engine Light (MIL)
- Failure to pass an emissions test
- Slight decrease in fuel efficiency (rare)
- Possible faint fuel odor near the vehicle
- No noticeable drivability symptoms
Likely causes
- Loose, corroded, or damaged wiring or connectors in the EVAP fuel vapor temperature sensor circuit
- Faulty EVAP fuel vapor temperature sensor
- Intermittent short to ground or voltage in the sensor wiring
- Poor ground connection for the EVAP system
- Faulty Powertrain Control Module (PCM) (rare)
What to check before replacing parts
Visually inspect the wiring and connectors associated with the EVAP fuel vapor temperature sensor.
Look for: Look for loose connections, chafed wires, corrosion, or physical damage that could cause an intermittent connection.
Perform a wiggle test on the sensor wiring harness while monitoring the sensor data on a scan tool.
Look for: Watch for sudden spikes or dropouts in the temperature reading on the scan tool when the harness is moved, indicating a loose connection or broken wire.
Check the resistance of the EVAP fuel vapor temperature sensor using a digital multimeter.
Look for: Compare the measured resistance to the manufacturer's specifications for the current ambient temperature. An out-of-spec or fluctuating reading indicates a faulty sensor.
Test the reference voltage and ground circuits at the sensor connector.
Look for: Ensure there is a steady 5-volt reference signal from the PCM and a solid ground. Intermittent voltage or high resistance on the ground indicates a wiring or PCM issue.
Check for related EVAP system codes or technical service bulletins (TSBs).
Look for: Other EVAP codes might point to a broader system issue, and TSBs can provide manufacturer-specific diagnostic steps or known issues related to this code.
This page explains the generic P2028 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
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