P2401
DTC P2401 Evaporative Emission System Leak Detection Pump Control Circuit LowDTC P2402 Evaporative Emission System Leak Detection Pump Control Circuit High
DTC Detection Condition:
DTC SUMMARY
DESCRIPTION
While the engine is running, if a predetermined condition (closed loop, etc.) is met, the EVAP VSV is opened by the ECM (Included in HV control ECU) and stored fuel vapors in the canister are purged to the intake manifold. The ECM will change the duty cycle ratio of the EVAP VSV to control purge flow volume. Purge flow volume is also determined by the intake manifold pressure. Atmospheric pressure is allowed into the canister through the vent valve to ensure that purge flow is maintained when negative pressure (vacuum) is applied to the canister.
The ECM monitors the condition of both the key-off monitor and purge flow monitor to ensure proper operation of the EVAP system.
Key-off monitor
This monitoring system checks for pump module malfunctions and leaks from the EVAP and closed tank systems. Be sure to leave the vehicle for at least 5 hours to sufficiently cool the fuel and stabilize fuel tank pressure. This makes EVAP system monitoring more accurate.
HINT: If the engine coolant temperature is 35 °C or more, 5 hours after the ignition switch has been turned off, the ECM (Included in HV control ECU) will begin performing a monitor check after another 2 hours. If the engine coolant temperature is still 35 °C or more, 7 hours after the ignition switch has been turned off, the ECM will begin performing a monitor check after another 2.5 hours.
There are two methods for monitoring the EVAP system.
1. If the fuel tank pressure is higher or lower than the atmospheric pressure, the system determines that there are no leaks in the closed tank system and the system will check for leaks from the piping and canister between the EVAP VSV and pump module. (Method A)
2. If the fuel tank pressure is almost the same as the atmospheric pressure, vacuum pressure will enter the fuel tank and the system will check for leaks from the fuel tank after checking for leaks from the canister. (Method B)
Purge flow monitor
If EVAP system pressure change is less than 7.5 mmHg (1 kPa) when the engine is running and the EVAP VSV is turned ON (closed), the ECM (Included in HV control ECU) determines that the purge flow is insufficient.
MONITOR DESCRIPTION
Monitor Strategy:
Typical Enabling Conditions (Part 1):
Typical Enabling Conditions (Part 2):
Typical Malfunction Thresholds:
1. P2401: Vacuum pump stuck OFF
In operation B, the vacuum pump creates negative pressure (vacuum) through the 0.02 inch orifice. The EVAP (Evaporative Emission) system pressure is then measured by the ECM (included in the HV control ECU) using the pressure sensor to determine the 0.02 inch leak pressure standard. If the pressure is higher than -1.06 kPa (-7.95 mmHg)* or lower than -4.85 kPa (-36.38 mmHg)*, the ECM interprets this as the vacuum pump being stuck OFF (not operating). The ECM then illuminates the MIL and sets the DTC (2 trip detection logic).
*: The threshold varies according to the atmospheric pressure measured in operation A. The values described above are based on an atmospheric pressure of 100 kPa (750.1 mmHg): absolute pressure.
2. P2402: Vacuum pump stuck ON
In operation B, the vacuum pump creates negative pressure (vacuum) through the 0.02 inch orifice. The EVAP (Evaporative Emission) system pressure is then measured by the ECM (included in the HV control ECU) using the pressure sensor to determine the 0.02 inch leak pressure standard. If the pressure is higher than -1.06 kPa (-7.95 mmHg)* or lower than -4.85 kPa (-36.38 mmHg)*, the ECM interprets this as the vacuum pump being stuck ON (remaining ON all the time). The ECM illuminates the MIL and sets the DTC (2 trip detection logic).
*: The threshold varies according to the atmospheric pressure measured in operation A. The values described above are based on an atmospheric pressure of 100 kPa (750.1 mmHg): absolute pressure.
HINT: The detection logic of DTCs P2401 and P2402 is the same because in both cases the 0.02 inch leak pressure standard measured in operation B is compared to the atmospheric pressure registered in operation A. The ECM calculates the difference between these pressures by deducting [the 0.02 inch leak pressure standard] from [the stored atmospheric pressure], and uses this to monitor the EVAP system pressure change.
MONITOR RESULT
Refer to CHECKING MONITOR STATUS. Checking Monitor Status
The test value and test limit information are described as shown in the given table. Check the monitor result and test values after performing the monitor drive pattern (refer to "Confirmation Monitor").
- MID (Monitor Identification Data) is assigned to each emissions-related component.
- TID (Test Identification Data) is assigned to each test value
- Scaling is used to calculate the test value indicated on generic OBD II scan tools.
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INSPECTION PROCEDURE