DTC P04F1

DTC P04F1  : Evaporative Emission (EVAP) System Low Purge Flow Detected

General Description 

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

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

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

Negative side purge flow	Boost side purge flow	Purge back-flow (P2450)	Condition
Flowing	Flowing	OK	Purge line normal, EVAP canister purge valve normal
Flowing	Flowing	NG (P2450)	Non-return valve A abnormal
Not flowing	Flowing	-	Negative side purge line abnormal
Flowing	Not flowing	-	Boost side purge line abnormal
Not flowing	Not flowing	-	Purge line abnormal, EVAP canister purge valve open

The fuel vapor in the fuel tank is temporarily stored in the evaporative emission (EVAP) canister and drawn into the engine through the EVAP canister purge valve. The powertrain control module (PCM) controls the amount of vapor introduced into the engine by varying the duty cycle of the EVAP canister purge valve according to the condition of the engine.

The PCM checks the purge flow conditions on both negative and boost pressure sides. If either side of the purge flow is detected as abnormal, it is determined that there is a clog or disconnection on the abnormal side of the purge line. If both sides of the purge flow are detected as abnormal, it is determined that the purge lines are abnormal or the EVAP canister purge valve is stuck opened.

Purge flow check of negative pressure side:

<STEP 1>

The EVAP canister purge valve opens normally (EVAP canister purge valve OPEN OK) and detects that the purge flow is normal when the pulse of the EVAP canister purge valve duty cycle is transmitted to the EVAP leak check module pressure sensor during purge flow (pulse method).

OK determination: Pulse exists (P0441 OK)

• P04F1 Purge flow OK
• P04DF EVAP canister purge valve stuck Open OK

NG determination: No pulse (P0441 NG)

• Either purge flow P04F1 abnormality or P04DF EVAP canister purge valve OPEN failure
• In this case, classify the failed part according to <STEP 2>

<STEP 2>

If there is no pulse, it is determined as either no purge flow or the EVAP canister purge valve is stuck OPEN:

When the EVAP leak check module pressure sensor fluctuates from negative pressure to atmospheric pressure after the vehicle condition is turned to the OFF (LOCK) mode: P04DF EVAP canister purge valve stuck OPEN

When there is no fluctuation of the EVAP leak check module pressure sensor: P04F1 purge flow NG

Monitor Execution, Sequence, Duration, DTC Type 

Execution	Once per driving cycle
Sequence	P0441 is judged as NG
Duration	-
DTC Type	Two drive cycles, MIL on

Enable Conditions 

Condition	Minimum	Maximum
Low load duration time	10 seconds	-
Wait for stability after the vehicle condition is turned to the OFF (LOCK) mode	10 seconds	-
Engine coolant temperature [ ECT Sensor 1 ] before EVAP purge control starts	131 deg.F (55 deg.C)	-
[ ] : HDS Parameter

Malfunction Threshold 

The output from the EVAP leak check module pressure sensor is less than 0.27 kPa (2.00 mmHg0.079 inHg).

Possible Cause 

Confirmation Procedure 

Operating Condition 

1. Start the engine. Hold the engine speed [ Engine Speed ] at 3000 RPM without load (in P or N) until the radiator fan comes on.
2. Let the engine idle for at least 55 seconds.
3. Drive the vehicle at high load for total of at least 9.5 seconds.
4. Turn the vehicle to the OFF (LOCK) mode and leave the vehicle for at least 10 seconds.

• 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.