Preface: I have a 2002 Jeep Wrangler that was swapped with a L83/6L90e from a 2015 Silverado. The original NP231 Tcase is in the Jeep. The speedometer and shift points are good in 2WD and 4HI. I did not do the swap, just working out issues for the owner.
The problem: 4Low is not great. Shifting sucks and even in manual mode some shifts are denied.
What I have discovered: The RPO for the VIN/OS shows a NQG T-case (manual shift t-case). Schematic shows speed sensor coming from T-case and going to ECM X2 pins 6 and 7. I have an empty spot in Pin 6. Looking at the 6L90e schematic, it shows Pin 8 is used for non- NQG (and if I'm reading it correctly only for 2WD vehicles). I do have a wire in Pin 8, but I have not confirmed it is my VSS. The calibration says VSS is 36 Pulse/Rev. The Jeep NP231 shows it is a 8 Pulse/Rev. The calibration also has a selection for where the VSS is located.
Question:
Can I wire the Jeep NP231 speed sensor to the correct Pin (6)?
Will I need to change the OSS/TOS tab to enabled? ([ECM] 14025 - OSS/TOS Physically Connected: OSS/TOS sensor is physically connected to the ECM (manual transmission, etc)
What is TOS electrical interface? It says value 0-16, and currently at 4. ([ECM] 14027 - TOS Electrical Interface: Indicates which TOS interface has the TOS sensor attached to it.)
Can I just change the VSS to 8 Pulse/Rev?
Also, I did find that the ECM has a ground switch input to signal 4Low. Since I found no other inputs telling the TCM that it is in 4Low, would it be safe to assume that this input will tell the trans to change to 4Low shift schedule?
Just a follow up in case anyone else needs the info.
I flashed the ECU back to stock with SPS2 and re-read the file so I could see exactly what has been changed prior to my work.
I found the VSS codes P2160 and P2161 both set to no error reported. Reset them to stock. I wired in the Jeep VSS and I can get it to read correctly. However, after a few drive cycles I get the code P2160. I can only assume that this is due to the fact the Jeep VSS is a 5v reference type and the stock GM one is a permanent magnet type. Since SI references the voltage range it should be in is 2-3v, and theres nothing I can find with HP Tuners to edit that logic, it's useless to use the Jeep VSS. Now, it seems that with the codes P2160 and P2161 set to no error, the ECM defaults to the transmission OSS reading. I have been driving it this way (and this is how the customer brought it to me), so I venture to say it's okay to do it this way. That is unless any expert on here wants to chime in and educate me.
The 4 Low correction was pretty easy. I just added a ground switch on the ECM 4 Low input (for me Connector X1 Pin 61). This and editing the Low Range offset in the ECM, the Speedo is correct and the shift points are spot on. The only thing you need to make sure is code P2771 is set to turn on 2nd error (factory setting), If it is set to no error, the VSS correction will not work.
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