DTC Advanced Diagnostics: P2421: General Description
The powertrain control module (PCM) can only detect if the evaporative emission (EVAP) canister vent shut valve is stuck open if it is commanded close because this is a normally opened valve. When the EVAP canister vent shut valve is commanded closed during the purge, the fuel tank pressure (FTP) sensor value lowers due to the decompression of the EVAP system. If the FTP sensor value does not lower, the PCM detects a malfunction and stores a DTC.
Monitor Execution, Sequence, Duration, DTC Type
| Execution | Once per driving cycle |
| Sequence | None |
| Duration | 80 milliseconds or more |
| DTC Type | Two drive cycles, MIL on |