DTC P2450: General Description

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

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

The powertrain control module (PCM) automatically 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 check module operation flow

• Reference pressure measurement : Malfunction detection in the EVAP leak check 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 check 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 check pressure sensor is produced by instantaneously opening the fuel vapor containment valve by closing the control valve of the EVAP leak check 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 kPa (0.3 inHg, 9 mmHg) or more) or a negative value (-2 kPa (-0.4 inHg, -12 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 system total (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.