DTC P04EF (2018 2019)
DTC P04EF: 0.02 inch Leak (Canister Leak)
General Description
The powertrain control module (PCM) starts the evaporative emission (EVAP) system diagnosis after the vehicle has been turned to the OFF (LOCK) mode, and has met all other enable conditions (initial engine coolant temperature [ECT Sensor 1] and off for at least 5 hours). The EVAP system diagnosis is performed by reducing pressure between the EVAP canister and the atmosphere. If pressure is reduced with the fuel vapor containment valve open, the entire EVAP system will be diagnosed, and if the fuel vapor containment valve is closed, only the EVAP canister side will be diagnosed.
EVAP leak detection module operation flow
- Reference pressure measurement : Malfunction detection in the EVAP leak detection module itself and determination of early completion of pressure reduction when normal.
- System pressure reduction : Pressure in the EVAP system is reduced to measure the ultimate pressure.
- Reference pressure re-measurement : Leak is detected by comparing with the ultimate pressure of the system pressure reduction.
- Reference value is to be measured twice considering change in the characteristics of the vacuum pump during detection.
Reference pressure is the pressure reduction by the reference orifice (#40 equivalent) in the EVAP leak detection module used to check for leak by comparison with the system pressure reduction.
Here is an overview of the malfunction detection :
Judgment 1: Normality judgment on the fuel tank side by measurement of the barometric pressure and fuel tank internal pressure. (P04EE) (Change in the leak detection module absolute pressure sensor is produced by opening the fuel vapor containment valve by closing the control valve in the EVAP leak detection module. The amount of the change (ΔP) is used to judge the fuel tank internal pressure)
- The fuel tank side is judged to be normal and Judgment 3 is performed if the ΔP is a sufficiently large positive value (1.3 kPa (0.4 inHg, 10 mmHg) or more) or a negative value (-1.3 kPa (-0.4 inHg, -10 mmHg) or less).
- The fuel tank side is judged to be near the barometric pressure and Judgment 2 is performed if the ΔP is a small value.
Judgment 2: Detection of the entire system (fuel tank side and canister side). (P04EF)
If the fuel tank side is judged to be abnormal in the fuel tank internal pressure (near the barometric pressure) in Judgment 1, the fuel vapor containment valve is opened to perform detection in the total system. If the pressure under the total system pressure reduction is lower than the pressure under the reference pressure reduction, the fuel tank side and the canister side are judged as normal (since the pressure is reduced). Also in this case, Judgment 3 is to be performed to detect malfunction in the fuel vapor containment valve. When the value of the pressure is high, Judgment 3 is to be performed to identify a malfunction (since the pressure is not reduced).
Judgment 3: Detection of the canister side. judgement 2 may be omitted depending on the result of Judgment 1)
Detection is to be performed on the canister side closing the fuel vapor containment valve. If judged to be normal in Judgment 1, only this detection is performed with the fuel vapor containment valve closed. If the pressure under EVAP canister pressure reduction is higher than the pressure under reference pressure reduction, A malfunction is detected (since the pressure is not reduced). In this case, the failed part is judged as follows according to the result of the previous judgment.
- When the fuel tank side is determined to be normal in Judgment 1, leak in the canister side is detected.
- When a malfunction is detected in Judgment 2, leak in the canister side is detected.
- When the fuel tank side and the canister side are normal in Judgment 2, a malfunction in the fuel vapor containment valve is detected if the fuel tank internal pressure changes when the EVAP canister pressure is reduced.
Monitor Execution, Sequence, Duration, DTC Type
| Execution | Once per driving cycle |
| Sequence | None |
| Duration | 22 minutes, 17 seconds or more |
| DTC Type | Two drive cycles, MIL on |
Enable Conditions
| Condition | Minimum | Maximum |
|---|---|---|
| Elapsed time after turn the vehicle to the ON mode | 10 minutes | - |
| Elapsed time after turn the vehicle to the OFF (LOCK) mode | 5 hours | - |
| PCM wake up engine coolant temperature [ECT Sensor 1] | 40 deg.F (5 deg.C) | 95 deg.F (35 deg.C) |
| Barometric pressure [Baro Sensor] | 76 kPa (22.5 inHg, 569 mmHg) | - |
| 12 volt battery voltage | 10.5 V | - |
| Other | No refueling is required | |
[ ]: HDS Parameter
Malfunction Threshold
Either of these conditions occurs:
When the fuel tank internal pressure is not near the barometric pressure.
| Leak detection module absolute pressure sensor at the time of the decompression | Malfunction judgment | DTC | |||
| Canister decompression | Judgment 1 | Judgment 2 | Judgment 3 | ||
| Reference pressure more than canister decompression | Normal | Normal | Normal | - | |
| Reference pressure is less than canister decompression | Normal | Failure | Normal | P04EF | |
When the fuel tank internal pressure is near the barometric pressure.
| Leak detection module absolute pressure sensor at the time of the decompression | Malfunction judgment | DTC | |||
| System total decompression | Canister decompression | Judgment 1 | Judgment 2 | Judgment 3 | |
| Reference pressure more than system total decompression | Fuel tank internal pressure is no change | Normal | Normal | Normal | - |
| Fuel tank internal pressure is change | Normal | Normal | Failure | P2450 | |
| Reference pressure is less than system total decompression | Reference pressure more than canister decompression | Failure | Normal | Pending | P04EE |
| Reference pressure is less than canister decompression | Pending | Failure | Pending | P04EF | |
Possible Cause
- EVAP system leak
- Fuel vapor containment valve leak
Confirmation Procedure
Operating Condition
- With the engine coolant temperature [ECT Sensor 1] within the specified range, turn the vehicle to the ON mode, and wait for at least 10 minutes.
- Turn the vehicle to the OFF (LOCK) mode, and wait for at least 5 hours.
- PCM wake up, and wait at least 22 minutes, 17 seconds.
With the HDS
Do the EVAP FUNCTION TEST in the INSPECTION MENU with the HDS.
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 or by disconnecting the 12 volt battery.