DTC Advanced Diagnostics: P04DF (2.0L Engine) (2024 2025)

DTC P04DF  : Evaporative Emission (EVAP) System High Purge Flow Detected

General Description 

Courtesy of HONDA, U.S.A., INC.

The evaporative emission (EVAP) system monitor detects leaks in the fuel supply system by inducing and utilizing negative pressure in engine idle and vehicle OFF (LOCK) mode. This monitor is also used for diagnosing both the EVAP canister purge valve and EVAP canister vent shut valve for rationality malfunctions. Fuel that evaporates from the fuel canister gets stored in the EVAP canister. The evaporated fuel trapped in the EVAP canister is occasionally flushed at the appropriate engine operating conditions into the intake manifold via the EVAP canister purge valve. The EVAP canister vent shut valve isolates the evaporative system from ambient air. Several steps are taken to detect for leakage in the fuel supply system. If the difference between the fuel tank pressure and its reference (start) value during compensation gradient determination measurement is a specified value, the powertrain control module (PCM) detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type 

Execution	Once per driving cycle
Sequence	None
Duration	0.5 seconds or more
DTC Type	Two drive cycles, MIL on

Enable Conditions 

General enable conditions to trigger EVAP system monitor 

Condition	Minimum	Maximum
Elapsed time since the last canister purging	-	30 seconds
Outside air temperature	32 deg.F (0 deg.C)	103.6 deg.F (39.8 deg.C)
Initial engine coolant temperature [ECT Sensor 1]	32 deg.F (0 deg.C)	113 deg.F (45 deg.C)
Barometric pressure [Baro Sensor]	74 kPa (555 mmHg, 21.9 inHg)	-

Condition	Minimum	Maximum
Fuel tank pressure	-4 kPa (-30 mmHg, -1.1 inHg)	4 kPa (30 mmHg, 1.1 inHg)
12 volt battery voltage [Battery]	10.7 V	25.6 V
Fuel level	0 L (0 US gal)	40.5 L (10.69 US gal)
Ratio between intake manifold pressure and barometric pressure	-	0.8
Fuel feedback	Closed loop
Other	No refueling
	Both EVAP canister vent shut valve and EVAP canister purge valve are commanded open for at least 20 seconds
	No excessive ambient pressure change for at least 5 minutes

Canister purging 

Condition
Other	Both EVAP canister vent shut valve and EVAP canister purge valve are commanded open

EVAP canister vent shut valve stuck check 

Condition
Other	EVAP canister vent shut valve stuck in closed position has not been detected
	EVAP canister vent shut valve is commanded open and EVAP canister purge valve is commanded closed

Pressure stabilization after purging 

Condition
Other	Fuel tank pressure has stabilized after purging for at least 3 seconds within 10 seconds

Phase A: Compensation gradient determination 

Condition
Other	EVAP canister vent shut valve is commanded closed

Malfunction Threshold 

The difference between the fuel tank pressure and its reference (start) value during compensation gradient determination measurement is less than -0.175 kPa (-1.32 mmHg, -0.0517 inHg).

Possible Cause 

Confirmation Procedure 

Operating Condition 

• Start the engine and drive the vehicle for a while.
• Stop the vehicle and let it idle for 10 minutes.

• Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.

Diagnosis Details 

Conditions for setting the DTC 

When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC, the freeze data, and the on-board snapshot are stored.

Conditions for clearing the DTC 

The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, the freeze data, and the on-board snapshot can be cleared with the scan tool clear command.