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Pressure control solenoid , Mechanically inop
Posted to Transmission Forum on 8/20/2016 8 Replies

Tearing my hair out here. First off though , let me stress ; THE PCM IS TRYING TO OPERATE THE PRESSURE CONTROL SOLENOID; 12volts at terminal G and there is a toggling ground via pcm at terminal F ( ie the 12v is being modulated by pcm ) so broken wires , terminals and PCM are not at fault here. Also the PC sol would not "Buzz " even when modulated Directly at the solenoid terminals in or out the car. ( although after an hour on the bench and the solenoid started to work again) Now , this car has been losing all gears ; po731 , p0732, po733 , and po734 have been setting after as little as 10 minutes or as many as 3 days of driving. When the DTCS set and car loses gears main line pressure falls to 60psi and reverse is effected also. While this happening the P/C solenoid is inop MECHANICALLY and "stuck " closed cutting off most line pressure through the Valve body. The PCM is still supplying a PWM toggle signal thru ct 1530 and power is verified through ct 1525. In Fact , applying power and ground to terminals F&G at the valve body connector and then even DIRECTLY TO the solenoid itself will not operate the solenoid when this happens .

I've replaced the Valve body twice , and the P/C solenoid once and it happens again. Even weirder , the old solenoid that was previously inop started working again after waiting an hour and sitting on the bench. while the good one that was just put in the Valve body quit after 10 minutes. My first thought was that debris or clutch material might be jamming the P/C sol ports , but the fluid is clean and the aftermarket pressure filter looks clean as well. Also just to reiterate why I believe the solenoid is either clogged or mechanically Inop when this occurs is because it will not "Click" when modulated , it stays "closed " even when fuse power is removed and Line pressure is too low at that time. Normally , if the PC solenoid fails , it fails mechanically open which causing LP to max out whether it's a bad solenoid , pcm or wiring, the solenoid passes max line pressure and of course the trans bangs and slams into gear.

I know it's not a pump issue or suction filter because after replacing the first 2 valve bodies and then the solenoid this AM , the LP went to 270# max and 140 # in reverse before the new solenoid quit .

Ray from California

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car Vehicle Data

1998 Saturn SC2 1.9L

Engine1.9 L
Trans4-speed Automatic (Electronic)