Grand Prix V6-204 3.4L DOHC (1992)
Chart C-8C (2 Of 2, 4th Gear Switch Diagnosis)
CIRCUIT DESCRIPTION
The PCM controls automatic transmission shift points by the use of solenoids inside the transaxle. The solenoids get power when the ignition is "ON",
and become energized when the PCM completes the circuit to ground. The PCM also monitors the transaxle through two pressure operated switches in
the valve body, the 1st gear switch and the 4th gear switch.
Fluid pressure closes the appropriate switch when that gear is engaged. The PCM applies a reference voltage to each switch and then monitors the
voltage in the circuit. When a switch closes, it grounds that circuit, causing a drop in the circuit voltage. Low voltage in the reference circuit to the
fourth gear switch, for example, indicates that 4th gear is engaged.
