DTC Advanced Diagnostics: P04F0
DTC P04F0:Evaporative Emission (EVAP) System Incorrect Purge Flow Detected

General Description

The powertrain control module (PCM) monitors second purge line which is used for regeneration of evaporative emission (EVAP) canister at full load (boost condition) for stuck closed detection. Second purge line has a mechanical non-return valve which prevents back purging of EVAP canister with boost pressure. The described test will detect low purge flow fault, which can be caused by non-return valve stuck closed malfunction. The second purge line monitoring will be performed in boost mode, when canister purging is performed using second purge line. As soon as enable conditions are fulfilled, the EVAP canister purge valve will be stimulated with the special pattern. In order to detect second purge line stuck closed fault, the fuel tank pressure oscillations are monitored during stimulation cycle of the EVAP canister purge valve. If no fuel tank pressure oscillations can be observed during EVAP canister purge valve open phase, the PCM detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type
Execution
Continuous
Sequence
None
Duration
0.5 second or more
DTC Type
Two drive cycles, MIL on

Enable Conditions
Condition
Minimum
Maximum
Outside air temperature
18.5 °F (-7.5 °C)
–
Engine coolant temperature [ECT Sensor 1]
140 °F (60 °C)
–
Engine speed [Engine Speed]
2,000 rpm
6,000 rpm
Boost pressure
10 kPa (75 mmHg, 3.0 inHg)
–
12 volt battery voltage [Battery]
10.7 V
–
Charging efficiency
80.02 %
–
Integrated purge mass flow after a longer purge stop
0.49 g (0.0173 oz)
–
Integrated mass flow at repeating EVAP canister purge valve diagnosis
0 g (0 oz)
–
Fuel feedback
Closed loop
[ ]: HDS Parameter

Malfunction Threshold
Both conditions occur:
Mass flow during diagnosis second purge line is 0 - 2.5 kg/h (0 - 5.5 lbs/h)*.
The pressure oscillation is less than 0.1875 kPa (1.406 mmHg, 0.05536 inHg) at least 3 times during the open phase of EVAP canister purge valve stimulation cycle.

*: Depending on diagnosis duration

Possible Cause
NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
EVAP canister purge valve stuck closed
EVAP canister purge valve stuck open
Purge line not connected
Non-return valve B stuck closed

Confirmation Procedure
Operating Condition
1.
Start the engine.
2.
Drive the vehicle at engine speed [Engine Speed] between 2,000 - 6,000 rpm with full load.
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 and the freeze data 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, and the freeze data can be cleared with the scan tool Clear command.