4L80E TRANS throwing P0753 and P0758 codes
Thread Starter
Joined: Feb 2003
Posts: 2,145
Likes: 133
From: East Chatham, New York
4L80E TRANS throwing P0753 and P0758 codes First, after swapping out the TH350 for the 4L80E, I put the two speed sensor connectors on the wrong sensor. At a dead stop, the speedometer was moving, but when leaving a stoplight, it did shift from first to 2nd but it would then proceed, at steady throttle, to upshift to 3rd, then immediately downshift to 2nd, repeating that over and over.
I polled some folks and they said it sounded like I had the speed connectors reversed. I swapped them and now, the speedometer on the dash is perfect, but it absolutely will not shift out of whatever gear (1st? 2nd?) that it's in when I slide the shifter past neutral and into gear. I can manually articulate the shifter to any gear but it stays in whatever gear it's in.
I read a bit on the 'net and some folks indicated the trans might not be getting 12 volts at the plug. I pulled the connector and it's got voltages. Next, I put it on jack stands and put it in drive. Using my HPTuners, I tried to make it shift to other gears while watching the speedo and tach. Nothing occurred in relation to shifting as a result.. but.... If I had elevated the throttle just a bit to say, 2,500 RPM, then manually downshifted the shifter in the console, I could hear and feel a 'clunk' as it dropped down a gear. It did that (clunked on each manual downshift) each time I clicked the shifter but not into first, stopping doing that when in 2nd gears position.
I'm really puzzled.
Nothing in HPTuners special functions makes it shift.
I polled some folks and they said it sounded like I had the speed connectors reversed. I swapped them and now, the speedometer on the dash is perfect, but it absolutely will not shift out of whatever gear (1st? 2nd?) that it's in when I slide the shifter past neutral and into gear. I can manually articulate the shifter to any gear but it stays in whatever gear it's in.
I read a bit on the 'net and some folks indicated the trans might not be getting 12 volts at the plug. I pulled the connector and it's got voltages. Next, I put it on jack stands and put it in drive. Using my HPTuners, I tried to make it shift to other gears while watching the speedo and tach. Nothing occurred in relation to shifting as a result.. but.... If I had elevated the throttle just a bit to say, 2,500 RPM, then manually downshifted the shifter in the console, I could hear and feel a 'clunk' as it dropped down a gear. It did that (clunked on each manual downshift) each time I clicked the shifter but not into first, stopping doing that when in 2nd gears position.
I'm really puzzled.
Nothing in HPTuners special functions makes it shift.
Thread Starter
Joined: Feb 2003
Posts: 2,145
Likes: 133
From: East Chatham, New York
Update - Sure enough, the appropriate pins weren't getting voltage. It turns out that in the fuse box under the hood, the fuse that feeds that particular circuit had a feeble connection. The fuse wasn't blown, it was just not connected sufficiently to feed the current. All is well now.
