DTC Advanced Diagnostics: P04F0 (2.0L Engine) (2024 2025)
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 | Once per driving cycle |
| Sequence | None |
| Duration | 0.5 seconds or more |
| DTC Type | Two drive cycles, MIL on |
Enable Conditions
| Condition | Minimum | Maximum |
|---|---|---|
| Outside air temperature | 18.5 deg.F (-7.5 deg.C) | - |
| Engine coolant temperature [ECT Sensor 1] | 140 deg.F (60 deg.C) | - |
| Engine speed [Engine Speed] | 1, 650 rpm | 6, 000 rpm |
| Difference between barometric pressure and modeled pressure in second purge line | 4 kPa (30 mmHg, 1.2 inHg) | - |
[ ]: HDS Parameter
| Condition | Minimum | Maximum |
|---|---|---|
| 12 volt battery voltage [Battery] | 10.7 V | 25.6 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*.
- The pressure oscillation is less than 0.188 kPa (1.41 mmHg, 0.0555 inHg) at least 3 times during the open phase of EVAP canister purge valve stimulation cycle.
*: Depending on diagnosis duration
Possible Cause
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
- Start the engine.
- 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, 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.