Hi all,

Im getting a P0758 trouble code for the B solenoid 2-3 shift after replacing the internal and external wiring harness on my 4l80e. I replaced the wiring because a wire had slightly metled on the exhaust and I knew I needed to replace it anyway because the O ring on the connector was bad causing fluid to leak into large round connector.

While driving, the transmission stays in what I believe is 3rd gear and will not upshift or downshift. Originally, after I did the wiring swap, I had zero throttle response which was due to a blown fuse. I replaced the fuse and it fixed that issue.

Logically, I would think that maybe my soldering job was bad considering the transmission shifted fined before I messed with the wiring. I tested each terminal on the transmissions main harness and I did not get a continuity beep on my multimeter for any of the wires.

My questions are:

1) Should the wires on the transmission connector have continuity when the connector is unplugged?
2) How do I test for continuity on those wires?
3) Is it possible that whatever caused the blown fuse damaged the 2-3 solenoid?

Im really trying to avoid dropping the pan again so any tips to help eliminate this issue without dropping the pan would be appreciated.

Thanks.

 

I once got a p0785 code which is for the 3-2 shift solenoid, real similar to what you have. It was really intermittent and hard to track down, but I eventually traced it to a wire shorted. To ground in the harness somewhere. I ran a new wire rather than tearing the car apart and its been fine for years now. To check the wires, you need to unplug the PCM connectors and the trans plug, then using a schematic to figure out what wires are what, do a continuity test between the two. Also check for continuity to ground and power. The wires that control the shift solenoids should only have continuity between the connectors. If you have no continuity then you have a broken wire somewhere. It seems like a daunting task, but if you take your time you should be able to narrow it dow to whether or not its a harness issue. I seriously doubt that something fried the solenoid, but I guess anything can happen, although I would lean more towards a wiring problem.

 

I've got a similar issue. It's throwing P0753 and P0758.
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 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 so 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 read a bit on the 'net and some folks indicated it might not be getting 12 volts. 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.. 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.

 

Use the "Dash Command" phone app and a Bluetooth OBD II adapter and take a short drive. What speed does Dash Command show you moving down the road? Is it a reasonable speed?

Rick

 

I'll give that a try. Thanks for the suggestion.

 

My problem was that I had rewired the large connector on my 4l80e and didnt notice that there are two yellow wires on that one connector. I simply had the wrong yellow wires connected together. I swapped connections and it was good to go. Mine wouldnt hunt for a gear, it wouldnt even shift out of first.