DTC Advanced Diagnostics: P1458: General Description

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

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

The evaporative emission (EVAP) leak detection system uses an engine off natural vacuum (EONV) method. The EONV method detects leakage from the change in fuel tank pressure via the fuel tank pressure (FTP) sensor with the engine off.

Here is an overview of the malfunction detection for the EONV method:

Judgment 1: Detection of atmospheric pressure failure

Judgment 2: Flickering of the FTP sensor

<Judgments 1 and 2 happen at the same time.>

Judgment 1: 

After the engine has stopped, the powertrain control module (PCM) monitors the variation of the FTP sensor output to detect atmospheric pressure, after keeping the canister vent opened for a specified duration to stabilize the pressure inside the fuel tank.

• If the pressure inside the fuel tank after a specified duration has not reached a specified value from the sensor zero point, a canister vent blockage is detected.

Judgment 2: 

After the engine has stopped, the PCM monitors the variation of the FTP sensor output to detect FTP sensor electrical noise failure, after keeping the canister vent opened for a specified time to stabilize the pressure inside the fuel tank.

• If the difference of pressure inside the fuel tank and an average value after a specified duration has exceeded a specified value for a specified duration, an FTP sensor electrical noise failure is detected.

Monitor Execution, Sequence, Duration, DTC Type