What does it mean?
P1646 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: EVAP Vent Solenoid Control Circuit Malfunction .
Symptoms
- MIL on with, in most cases, no change in how the engine drives
- EVAP monitor never completes, so the vehicle is not ready for an emissions test
- Fuel tank hisses strongly when the cap is opened, or the tank is hard to fill and the nozzle keeps clicking off
- Occasional fuel vapour smell around the rear of the vehicle
- Additional EVAP leak or purge codes stored alongside this one
Likely causes
- Vent solenoid coil open or shorted internally
- Corroded connector at the vent valve, which sits near the charcoal canister and is exposed to road spray and salt
- Chafed or rodent-damaged harness along the underbody run to the canister
- Open or shorted control wire between the solenoid and the module
- Blown fuse on the solenoid supply side
- Solenoid seized with dirt, water or mud so it draws abnormal current
- Failed output driver in the control module
How to fix it
- Locate the vent valve at the charcoal canister and inspect its connector and the harness for corrosion, water and physical damage
- Command the vent valve open and closed with a scan tool and listen or feel for it clicking
- Measure the solenoid coil resistance and compare it with specification
- Check for battery voltage on the supply side of the connector with the ignition on, and check the related fuse
- Test the control wire back to the module for continuity and for shorts to ground and battery voltage
- Replace the vent solenoid if it is open, shorted or mechanically seized, and clean any dirt from its mounting area
- Repair harness damage, then clear the code and run a drive cycle to confirm the EVAP monitor completes