Park Avenue V6-231 3.8L VIN L SFI (1993)
Transaxle Solenoid & Driver Circuits
CIRCUIT DESCRIPTION
The purpose of the Transmission Converter Clutch (TCC) feature is to eliminate the power loss of the torque converter stage when the vehicle is in a
cruise mode. Two PCM controlled solenoids, located inside the transaxle, regulate fluid pressure to the torque converter clutch. One solenoid (the TCC
solenoid) provides fluid pressure to engage the TCC, the other solenoid (the Pulse Width Modulated or PWM solenoid), regulates pressure for a
smooth apply.
The solenoids get battery power when the ignition is turned "ON", and become energized when the PCM completes the circuit to ground. When the
TCC solenoid coil is activated ("ON,") fluid pressure applies the torque converter clutch, making a straight mechanical coupling between the engine
and transmission. When the TCC solenoid is deactivated, fluid pressure to the TCC is released and the torque converter clutch disengages, allowing the
torque converter to operate in the conventional manner (fluid coupling between engine and transaxle).
The TCC brake switch is connected in-line with the power supply to the TCC solenoid and is used to interrupt power to the solenoid when the brake is
applied. The PCM monitors voltage in the power supply circuit after the brake switch, at the TCC brake input terminal (BA5). Low voltage at this
terminal (zero or near zero) indicates the brakes are being applied. The PCM then disables TCC and PWM solenoid operation until conditions for apply
are again present.
TCC will engage when the following conditions are present:
^
Engine warmed up.
^
Vehicle speed above a calibrated value (about 28 mph 45 km/h).
^
Throttle position sensor output constant, indicating a steady road speed.
^
Brake switch closed (12 volts present at TCC brake input terminal of PCM.)
TEST DESCRIPTION
Numbers below refer to circled numbers on diagnostic chart.
1.
Checks operation of transaxle test box, power supply from ignition to solenoids, and that solenoid driver circuits are not grounded.
2.
Checks that TCC apply solenoid driver, inside PCM, is operating.
3.
Checks that TCC PWM solenoid driver, inside PCM, is operating.
4.
Do not measure resistance until the ignition has been turned "OFF" for at least 10 seconds to ensure that the PCM has powered down completely.
DIAGNOSTIC AIDS
The "SCAN" tool only indicates if the PCM has commanded the TCC solenoid driver "ON". This does not confirm that the TCC has actually applied.
To determine if the TCC is engaging properly, road test the vehicle. Engine rpm should decrease when the "Scan" indicates the TCC driver has turned
"ON".
