03 Will Not Downshift!!

Shagnasty · 11-01-2009, 10:31 AM

So its an 03 with the LB7 engine. Truck wont shift from 3rd to 4th or sometimes it will BANG!! through the gears and get stuck in 5th and will not downshift. Check Engine came on with P0700 Tran Ctrl Sys Error P0748 Pres Ctrl Solenoid Electrical. This just started happening in the last couple days.Never once had a problem with the transmission. Its dead in the water now does it every time, cant drive it.

C-Power · 11-01-2009, 10:36 AM

id pri change that shift syliniod........sounds like thats your problem

**ob_1jr** · 11-01-2009, 10:38 AM

P0748 Pres Ctrl Solenoid Electrical

treyfox11 · 11-01-2009, 10:39 AM

yeah i think you might have a bad sol

DuramaxSMOKE11 · 11-01-2009, 10:43 AM

shift soleniod or weak valve in the body

Shagnasty · 11-01-2009, 10:56 AM

haven't worked with this tranny very much, just enough to put a deep pan on it.

Is there a way i can test the soleniod to make sure thats the problem?

C-Power · 11-01-2009, 11:15 AM

get a good scan tool/computer like OTC Genysis or Pegysis or a snap-on one and you can take it for a drive and engage it....i think....i've never tried on an allison but on all others you can...