Automatic Transmission Nag1 - Service Information: Solenoid: Operation: Solenoids: Notes

WARNING: This page is about a different car, the 2008 Dodge Magnum, 2008 Dodge Charger, and 2008 Chrysler 300. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: A scan tool can only display a estimated pressure based on the current fed to the solenoid. Therefore if there's a stuck Line Pressure Regulating valve and the transmission has insufficient pressure, the scan tool will still display estimated MOD and Shift pressures because the solenoids are being fed the correct amount of current.

The solenoids are fed a 12-volt source from the TCM (Transmission Control Module). When an electrical current is applied to the solenoid coil, a magnetic field is created which produces an attraction to the plunger, causing the plunger to move and work against the spring pressure and the load applied by the fluid the valve is controlling. The plunger is normally directly attached to the valve which it is to operate. When the current is removed from the coil, the attraction is removed and the plunger will return to its original position due to spring pressure.

The plunger is made of a conductive material and accomplishes this movement by providing a path for the magnetic field to flow. By keeping the air gap between the plunger and the coil to the minimum necessary to allow free movement of the plunger, the magnetic field is maximized.