I have code 1645 on my 1998 caddy sts - STS Cadillac Cars & Trucks

DTC P1645 Evaporative Emission (EVAP) Purge Solenoid Control Circuit .
The PCM contains chips called Output Driver Modules that provide 7 switchable ground outputs for operating solenoids, relays, telltales, and other devices. Each of these ground outputs has fault lines that feed back to the PCM's 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 0 volt since it is grounding the output. If it receives 0 volt when the output is OFF or 12 volts when the output is ON, it sets the fault line low. DTC P1645 is used to monitor the fault line of the EVAP Purge Valve.
The purge solenoid is open or there is an open on the B+ voltage supply to the solenoid or the PCM is bad . Now , all you have to is test the electrical circuit to find out which it is ! Or maybe it would be best for you to take your vehicle to a qualified repair shop .

Amy, DTC P1645 Evaporative Emission (EVAP) Purge Solenoid Control Circuit. You may want a good Tech, to diagnose and estimate repair. Check the attached links,instruction and guides, Good luck
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Need help to solve P1645 code
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