EXPERTEC Technical Service Bulletins (7-92-109)

EXPERTEC TECHNICAL SERVICE BULLETINS

TECHNICAL SERVICE BULLETIN

PULSE WIDTH MODULATED (PWM) SOLENOID USED ON THE TORQUE CONVERTER CLUTCH CIRCUIT (TCC) - 4T60-E TRANSMISSIONS USED WITH THE 3800 ENGINE

Model(s): Oldsmobile Models equipped with 4T60-E Transmission with the 3800 (VIN L and 1) Engine

Bulletin No.: 7-92-109

Date: July 1, 1992

SERVICE INFORMATION

4T60-E transmissions with the 3800 (VIN L and 1) Oldsmobile application use a Pulse Width Modulated (PWM) solenoid to control transmission fluid flow to the Torque Converter Clutch (TCC) solenoid. The apply/release feel of the torque converter is controlled by varying the PWM solenoid duty cycle. This allows for a very smooth engagement/release of the Torque Converter Clutch during all driving conditions.

TCC apply is controlled by the PWM solenoid and the TCC solenoid. Both components are controlled by the Powertrain Control Module (PCM). The PCM monitors vehicle speed, throttle angle, transaxle gear range, and engine coolant temperature.

Voltage is supplied through the ignition switch while the PCM provides the ground to energize, the TCC and PWM solenoids. The PWM solenoid regulates pressure entering the PWM passage to the converter clutch regulator valve (Fig 1 ). This controls the converter clutch apply pressure. If the solenoid fails or engine parameters do not allow the solenoid to energize, full line pressure passes to the converter clutch regulator valve giving a more noticeable TCC engagement. If the TCC solenoid is not turned "on", the PWM solenoid will have no affect on converter clutch apply.

The PCM controls the PWM solenoid by varying its operating duty cycle from 0% to 100%. At 0% duty cycle, the PWM solenoid allows full line pressure to the converter clutch regulator. Maximum TCC regulated line pressure will give a harsh apply/release. If the PWM solenoid is at 100% duty cycle it will allow minimum pressure to the converter clutch regulator. The regulator will allow low pressure fluid to the TCC and the TCC will slip or may not apply.