P0456 - Evaporative Emission System (EVAP) Leak Detected (very small leak)
System
Powertrain (Engine & Gearbox)
Technical Description
The control module has detected a fault in the Evaporative Emission System (EVAP) Leak Detected (very small leak) (P0456).
Multimeter Test Points & Nominal Values
| Test Point / Component | Measurement | Nominal Target Range | Test Condition |
|---|---|---|---|
| Evaporative Emission System (EVAP) Leak Detected (very small leak) – Coil Resistance | Resistance (Ω) | 3 - 30 Ω (typical) | Connector disconnected at 20°C |
| Evaporative Emission System (EVAP) Leak Detected (very small leak) – Duty Cycle | PWM (%) | 5 - 95 % (modulates with target) | Engine running, actuator in control |
| Evaporative Emission System (EVAP) Leak Detected (very small leak) – Supply Voltage | Voltage (V) | 11.8 - 14.4 V | Ignition ON at connector |
Connector disconnected at 20°C
Engine running, actuator in control
Ignition ON at connector
Oscilloscope Waveform Analysis
2 ms/div, 20 V/divPossible Causes
Mechanical sticking or debris/carbon contamination jamming Evaporative Emission System (EVAP) Leak Detected (very small leak)
Chafed or pinched wiring harness along the signal path to Evaporative Emission System (EVAP) Leak Detected (very small leak)
Internal mechanical wear or carbon deposits inside Evaporative Emission System (EVAP) Leak Detected (very small leak)
Defective internal output driver or reference circuit in the control module for Evaporative Emission System (EVAP) Leak Detected (very small leak)
Symptoms
4
Recommended Solution
Remove component and inspect for carbon deposits or foreign debris preventing full mechanical closure.
Verify loaded supply voltage and harness terminal pins at Evaporative Emission System (EVAP) Leak Detected (very small leak).
Check circuit continuity and ground-side voltage drop (< 0.05 V) for Evaporative Emission System (EVAP) Leak Detected (very small leak).
Check supply and the low-side driver at the ECM connector. Replace the actuator or repair the circuit based on the readings.
Mechanic's Tip
Use the scan-tool output test with the scope on the control side at the same time. If duty changes but the actuator does not move, the valve is stuck — not the electrical fault you were chasing.