4l80e + 5.3L OS: 12216125, Shifts into 2nd immediately at 1mph, then goes 2-3-2-3-2-3

[kingtal0n]

Hello, I just started driving my swap, its a 5.3 + 4l80e (2002 model from a chevy 1500) it has a HD2 shift kit.

I will upload tune and scan soon. For now, just in case this is a simple common issue, pretty much as soon as I start moving from a stop, it shifts into 2nd right away. IF I put it into 1st manually I will hold 1st. It will also downshift 1st from 2nd manually.

Once it gets up in speed a little, it goes 2->3, and then right away kicks back and forth between 2 and 3. At first this seemed like a tire-speed + rear gear issue so I corrected my speedo for the rear gear and tire size, but it still happens exactly like before. In fact nothing seems to have changed even though I adjusted all my shift points, it still shifts when it wants to.

Once I get enough speed, it sticks to 3rd finally. So it must be in the computer telling it to up and down shift. Then it goes to 4th also just fine.

for now, any suggestions, <3 thank you. Otherwise, I will continue to diagnose and examine the issue till I figure it out!

[kingtal0n]

I've been looking at my logs and it looks like I am getting false MPH. Even when in park, it shows me at 15 to 19mph. No clue what is causing that- faulty VSS? Which VSS feeds the computer, there are 2 on my transmission. I dont Know?

It looks like this. Sitting in neutral I see 19mph ish. Then, I goto D4, and it jumps down to 1mph once I start moving. I am guessing the trans jumps into 2nd because it still "sees" 19mph from beforehand. I look more closely, when I approach 18~ mph the VSS drops to 14~ and back to 19. it keeps doing this, thus I see why It continually goes 2-3-2-3-2-3.

In fact, the VSS is following RPM. Now that I look even more, I see when it shifts from 1-2 manually my MPH drops with RPM. Weird!

So my question at this point, do both VSS sensors on the 4l80e output the same thing, does this sound like a VSS issue? or something internal to the trans.

[kingtal0n]

files,
tune file 5.3 4l80e 2002.hpt

17-05-19 21-13-06.hpl

17-05-19 21-29-39.hpl

VSS follows RPM when it feels like. I am going to enable some of the DTC that mention "VSS" then change the VSS sensors, then ??

[kingtal0n]

Turned out, my VSS sensors wires were switched around. for reference, purple wire pair (and yellow?) is for rear of trans. The red/blue plug wires you wired into the 4l60e harness is for the front vss.

17-05-20 21-49-17.hpl

Log of the first drive ever, 26 minutes on swap. Used the above tune exactly. 5.3 stock internals, Fuel pressure is 44psi constant, using the stock 240sx fuel pump still, OEM LS-1 injectors, LS1 intake, single turbo (oem truck manifolds) with gate held open for no boost (makes the engine less efficient). A/F was 15.2~ cruising and ranged from 13 to 14.7 at stops. NO narrowband O2 sensor, open loop, wideband visual

driving absolutely perfect, felt lockup and held lockup when and like it was supposed to.

[monte4ever]

Good job figuring this out. Wish I could do the same with my issue.

[chakal95]

files,
tune file 5.3 4l80e 2002.hpt

17-05-19 21-13-06.hpl

17-05-19 21-29-39.hpl

VSS follows RPM when it feels like. I am going to enable some of the DTC that mention "VSS" then change the VSS sensors, then ??

Hey, I currently have a LQ4/4L80 combo from a 2002 Silverado 1500HD with the P01 PCM and a 12212156 OSid. I am wanting to add a Flex Fuel sensor to the setup and i came accross the attached tune file which has the Flex Fuel Sensor capability and 4L80 segment.

Now my question is, in order to use this file with my setup would the only change needed be to replace all the tune information with that of my 6.0L file ?

I appreciate any help provided.

Thank you.

[monte4ever]

If the above file has ALL the Flex Fuel tables populated then yes.