Alright guys i need some help i have been searching the internet for quite some time and i cant seem to find anything helpful so hopefully one of you great guys might be able to point me in the right direction. First of all my car which is a 97 3.8l started to have harsh engagements from park to drive or reverse or neutral to drive or reverse also when shifting from 1st to 2nd it is extremely harsh and going into overdrive at fifty it is also very harsh all other shifts seem normal. this started over a year ago and i cant remember what code i was getting but i do know i replaced all of the shift solenoids but still the problem persisted, so i then went ahead and changed out the transmission for another used 4l60e but the problem never lessened up or went away. I have tried resetting the pcm by disconnecting the battery and pulling the fuse the whole nine yards (didnt help) and now i'm still getting these harsh shifts every time its not intermittent. i recently got the codes and apart from a few running rich codes the only one that i am getting related to the transmission is po748. please if anybody has any ideas and suggestions im up for anything. the other codes i found were po1406 po141 140 172 175 148 thanks guys

 

i would look at the wiring harness that goes back to the trans. most of these codes sensors are area.

 

P0748 - Pressure Control Solenoid 'A' Electrical

Possible Causes:
- Dirty transmission fluid
- Low transmission fluid level
- Faulty line pressure solenoid valve 'A'
- Line pressure solenoid valve 'A' harness is open or shorted
- Line pressure solenoid valve 'A' circuit poor electrical connection

- Dirty transmission fluid
- Low transmission fluid level
- Faulty line pressure solenoid valve 'A'
- Line pressure solenoid valve 'A' harness is open or shorted
- Line pressure solenoid valve 'A' circuit poor electrical connection

That would explain your hard shifting.

P1406 - Faulty EGR Valve

Clean or replace

P0141 - O2 Sensor Heater Circuit Malfunction B1 S2

Heater circuit for the O2 isn't working, could be bad fuse, short to ground, bad wiring, or the heater part of the sensor itself is broke.

P0140 - O2 Sensor Circuit No Activity Detected Bank 1 Sensor 2

O2 is sending the PCM a consistent voltage. Bad wiring, short to ground or bad sensor. Also, pausible bad injectors, wrong fuel pressure.
P0172 - System Too Rich Bank 1

P0175 - System Too Rich Bank 2

P0148 - Fuel Delivery Error

The P0172, P0175, and P0148 all through me for a loop. P0172 and 175 show too much fuel while P0148 will be thrown when the computer detects the system running lean under acceleration.