Faulty Evaporative Emission Vent Solenoid
Evaporative Emission Vent Solenoid harness is open or shorted
Evaporative Emission Vent Solenoid circuit poor electrical connection
Engine Light ON (or Service Engine Soon Warning Light)
Code P1645 Buick Description
The Powertrain Control Module (PCM) contains Output Driver Modules (ODM) that provides 7 switchable ground outputs for operating solenoids, relays, indicator lights, and other devices. Each of these ground outputs has fault lines that feedback to the PCM microprocessor. When the output is off, the output driver should receive the 12 volts fed to the solenoid, relay, etc. When the output is on, it should receive zero volts, since it is grounding the output. If PCM sees zero volts when the output is off or 12 volts when the output is on, it sets a fault line low. The Diagnostic Trouble Code (DTC) is used to monitor the fault line of the EVAP control solenoid. With the engine runtime over 10 seconds, the PCM detects that the EVAP Solenoid Circuit line was low, conditions met for 2 seconds, and the DTC sets.
P1645 Buick Code – Evaporative Emission Purge Solenoid Output Circuit