DTC P04DF: General Description

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

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

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 EVAP system equips two EVAP canister purge valves in parellel and adjusts the amount of vapor by driving EVAP canister purge valve 2 when EVAP canister purge valve 1 is fully opened.

<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). If there are no pulsation with EVAP canister purge valve 1, it judges pulsation by switching to EVAP canister purge valve 2 drive in EVAP canister purge valve 1 drive area.

OK determination: If pulsation from EVAP canister purge valve 1 drive area and pulsation from EVAP canister purge valve 2 area (EVAP canister purge valve 1 is in fully opened driving condition) are both present. (P0441 OK/P145E OK)

• P04F1 Purge flow OK
• P04DF EVAP canister purge valve 1 stuck Open OK
• P04AE EVAP canister purge valve 2 stuck Open OK

NG determination: If pulsation from EVAP canister purge valve 1 drive area is not present but pulsation from EVAP canister purge valve 2 drive is present. (P0441 NG/P145E OK)

• Either purge flow P04F1 abnormality or P04DF EVAP canister purge valve 1 OPEN failure.
• In this case, classify the failed part according to <STEP 2>.

NG determination: If pulsation from EVAP canister purge valve 2 drive area is not present but pulsation from EVAP canister purge valve 1 drive is present. (P0441 OK/P145E NG)

• Either purge flow P04F1 abnormality or P04DF EVAP canister purge valve 1 OPEN failure.

NG determination: If pulsation from EVAP canister purge valve 1 and EVAP canister purge valve 2 drive area are not present. (P0441 NG/P145E NG)

• P04F1 purge flow NG

<STEP 2>

If there is no pulse on EVAP canister purge valve 1, it is determined as either no purge flow or EVAP canister purge valve 1 stuck OPEN:

• When the EVAP leak check module pressure sensor fluctuates from negative pressure to atmospheric pressure after the engine stop: P04DF EVAP canister purge valve 1 stuck OPEN
• When there is no fluctuation of the EVAP leak check module pressure sensor: P04F1 purge flow NG

If there is no pulse on EVAP canister purge valve 2, it is determined as either no purge flow or EVAP canister purge valve 2 stuck OPEN:

• When the EVAP leak check module pressure sensor fluctuates from negative pressure to atmospheric pressure after the engine stop: P04AE EVAP canister purge valve 2 stuck OPEN
• When there is no fluctuation of the EVAP leak check module pressure sensor: P04F1 purge flow NG