CODE PO748 help

[fceja818]

I have a 1997 c1500 4.3 4L60E automatic Transmission with an Intermittent PO748.
Transmission rebuilt 2 years no issues till a month ago..

My symptoms are

Intermittent 1-2Harsh Shift at 1st it did ones in a while. I noticed it jerked on the 1st and 2nd shift on driving out of the parking a lot then I parked it and waited a few hours and it was gone on driving then a few weeks ago.i noticed it did it straight for a few weeks with no check engine light on but after that I scan the pick up and It did have the PO748 and 1870 Codes? But still no check engine light on.
I did throw parts at it replaced both Shift Solenoids A and B with the 3-2 and the Pwd not exactly sure on the name but that solenoid too.

I did upgrade the 1-2 accumulator to the sonnax pinless piston. No change in the symptoms it goes by shifting normal to the 1 - 2 hard shifts.

How do I go by diagnosing this without throwing in more parts blindly. If I can't figure it out then I have to find a transmission shop.and take it in. I'm not a mechanic but I'm very mechanically inclined.

 

[fceja818]

I have a 1997 c1500 4.3 4L60E automatic Transmission with an Intermittent PO748.
Transmission rebuilt 2 years no issues till a month ago..

My symptoms are

Intermittent 1-2Harsh Shift at 1st it did ones in a while. I noticed it jerked on the 1st and 2nd shift on driving out of the parking a lot then I parked it and waited a few hours and it was gone on driving then a few weeks ago.i noticed it did it straight for a few weeks with no check engine light on but after that I scan the pick up and It did have the PO748 and 1870 Codes? But still no check engine light on.
I did throw parts at it replaced both Shift Solenoids A and B with the 3-2 and the Pwd not exactly sure on the name but that solenoid too.

I did upgrade the 1-2 accumulator to the sonnax pinless piston. No change in the symptoms it goes by shifting normal to the 1 - 2 hard shifts.

How do I go by diagnosing this without throwing in more parts blindly. If I can't figure it out then I have to find a transmission shop.and take it in. I'm not a mechanic but I'm very mechanically inclined.

I did erase the codes and the only one that returns on and off is the PO748

 

[east302]

How do I go by diagnosing this without throwing in more parts blindly. If I can't figure it out then I have to find a transmission shop.and take it in. I'm not a mechanic but I'm very mechanically inclined.

The GM service manual will have the diagnostic procedure for each code. The manuals can be downloaded at this link, see post #92 for year 1997:

88-98 Service Manuals

Some heroes don't wear capes. Thanks everyone.

www.gmt400.com

 

[Schurkey]

For the record, that's a P ZERO 748, not a P OH 748.

P0748 not PO748.

As said, the service manual will have the complete diagnostic procedure.

 

[fceja818]

For the record, that's a P ZERO 748, not a P OH 748.

P0748 not PO748.

As said, the service manual will have the complete diagnostic procedure.

Yes I know it's a 0 not o it was late at night and I type it fast

 

[fceja818]

Yes I know it's a 0 not o it was late at night and I type it fast

Thanks I'll look into the Diagnosituc procedures after work today