Solenoid Application Charts
Transmission solenoids are electro-hydraulic actuators that the TCM uses to control the flow of pressurized transmission fluid throughout the transmission. The solenoid application chart below is used to diagnose automatic transmission shift problems.
![Transmission solenoid chart showing the symptoms of a bad shift solenoid A.](graphics/transmission-solenoid-chart-2.png)
The chart reveals that activating shift solenoid A causes the transmission to shift into the first and fourth gears. The TCM powers solenoid B to shift into first and second.
It contains two shift valves, A and B, that provide four different shift valve combinations. The TCM powers both solenoids for first, solenoid B for second gear, neither for third and solenoid A for fourth.
![Clutch and band application chart.](graphics/clutch-band-app-chart-ex.png)
Solenoid or clutch and band charts help a technician quickly interpret which solenoids and friction devices are activated for each gear. Through elimination, a technician can determine if it's electrical or mechanical.