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4 low signal

06 H3

a.k.a. "The Jackal"
Messages
9,506
Location
Meridian, ID
This is probably a question for ATVspeed or Reloader but I’ll put it here for everyone to learn as I’m sure the future will bring more modifications to the table and possibly transfer case swaps.

My issue: I installed a doubler transfer case. 1:1, 1.96:1, 2.72:1, 5.33:1. Its actually not an issue, it’s a badass setup that will greatly improve capability! It does causes issues, but I know they can be overcome.

My VSS is in a similar position to factory, it’s in the tail housing of the transfer case. Most guys that have done LS swaps in their jeeps have this issue too so to remedy it they put the VSS in the tailhousing of the trans so it always reads 1:1. I don’t want to do that, gotta pull the trans apart, drill and tap the tailhousing, etc. It isn’t a big deal if your doing it during the swap but to pull it all back out is a pain. The issue occurs that the VSS is seeing reduction in the tailhousing because the tcase is in low but the computer thinks it’s in 4 high. It freaks the **** out and cuts power, shifts weird, almost like a limp mode.

My original plan was to just bolt the encoder motor off the frame rail, push the 4low button so the computer knows it’s in 4low and we move on. Well I got too excited and drove it around and broke my encoder motor because I didn’t mount it. I kind of forgot that I left it on a skid plate and it bounced around. Instead of buying a new encoder motor to play dumb I want to actually fix it with a real solution.

So I hit the interwebs and found there is a 4low signal (I’ll post the wiring diagram) how it works is the encoder motor has wiring that goes to the TCCM (transfer case control module) behind the glove box. It then has an output that goes to the pcm that says “hey pcm! I’m in 4 low” then an output/input class 2 data wire that goes to the DIC, from what I understand it illuminates the lights and shows your 4 low button lighting up, your traction control off and stabilitrac off on the DIC and the traction light on the dash.

So to trigger the pcm 4 low signal it needs to be grounded out, so I bought a 2 prong switch, tapped into the wire between the TCCM and PCM and ground it out.

So I flip the switch and nothing on the dash lights up. I figured that may be the case. Since I tapped into the 4low switch in front of the tccm so it can’t trigger the DIC so my question is, does the pcm see a 4 low signal and cut out stabilitrac and traction control too but doesn’t illuminate it because the ground is after the TCCM? Or does it tell the pcm “use your 4 low shift tables” but leave traction control and stabilitrac engaged? I hope it disables it but doesn’t illuminate because I don’t want that crap on when in low range and the factory shuts it off in low range anyways.

With all that said, I would like to get the lights to illuminate when it’s all said and done so it looks factory but for next week I just need it to work whether the lights show up or not. I will be doing 3 days of backdoor KOH recovery. Rolling rigs over, and extracting broken ones out after the race and I don’t want to be fighting this stupid trans.

On another unrelated note, I did install a RADesigns mini rail shifter and TCC lockup. Since I have so many options hearing wise now I want to be able to start in any gear. I tapped into the TCM wiring with a on/on 6 prong switch. It allows factory control like a stock H3 with the toggle down and in the up position it gives me full manual control. If I want to start in 4th gear, I can start in 4th, it’s like a full manual valve body but still retains OE functions! Then for TCC lock up I have a on/off/on 3 prong switch. Toggle down is factory torque converter lock up, toggle in the middle is TC lock up is off, toggle up is TC lock up when I want it to. The more control I have when wheeling the better. Then flip both the switches to factory and it will allow any one to drive it like a normal vehicle.
 

JPaul

Well-Known Member
Messages
2,436
Location
Way up north, UT
Would it work to take the guts of the encoder apart and wire in the portion of the sensor that indicates it's in 4-low to the switch you added? Sounds like simply wiring to ground isn't enough, I am betting there is a resistor in there or something. I looked at the schematic and it doesn't give any details about the guts of the encoder motor, but it's a multi path circuit so it's not using a data line, so that is good at least. If the encoder motor is functionally useless now then it would not hurt to crack it open and see what is in there.
 

06 H3

a.k.a. "The Jackal"
Messages
9,506
Location
Meridian, ID
I could try cracking it open and seeing what it does. You think by grounding it out it isn’t doing anything? I’d drive it to see if it freaks out but I’m away from the vehicle till the end of the week
 

atvspeed4

Well-Known Member
Messages
1,214
Location
massachusetts
I have to check my notes but I don't believe this is a ground based system where you can just touch a lead to ground. I know there is a high and low reference but not sure if it is to ground or some other specific voltage like +1.2v
 

06 H3

a.k.a. "The Jackal"
Messages
9,506
Location
Meridian, ID
I have to check my notes but I don't believe this is a ground based system where you can just touch a lead to ground. I know there is a high and low reference but not sure if it is to ground or some other specific voltage like +1.2v

Please let me know! I grounded out the B5 wire between the pcm and tccm

c1ebd03a42ffb6dff95d648cf357eca9.jpg
 

JPaul

Well-Known Member
Messages
2,436
Location
Way up north, UT
I think it's a resistor or something because in the wiring schematics on Schwartzy's site it indicates a low ref line which usually means there is a (typically) 5v input and then at least one signal output and the low ref is basically the ground for the sensor, and generally the signal line(s) provide a variable voltage signal via a resistor network or potentiometer. An example is the throttle body position sensor or the throttle pedal sensors.

You could even just put a meter between the low ref line and the 4lo signal line to see if there is a resistance value and compare it to the others. The schematic was not clear as to what line is really what aside from the low ref signal.

There are 5 wires to the encoder, one is ground (low ref) so that leaves 4 others. They may indicate 4hi, 4hi locked, neutral, and 4lo. But there may be more complexity to it than that. I'd start with putting a meter from low ref to each of the other 4 lines to see what kind of readings you get. You may need to cycle the motor through its positions to get anything.

Sent from my SM-N975U using Tapatalk
 

CaseyS

Well-Known Member
Messages
755
Location
Louisiana
I did not get this circuit to work with my standalone. It would seem like the TCCM would ground that pin in 4LO but I recall trying to wire that way and it not working.

I would say to try the other way and assert it high not low (put +12v) to the input but I would be nervous to try that. You would have to find a working vehicle and probe the voltage on that PCM input pin to determine if the voltage is high or low in 4LO.

The easy answer at this point is to just get an encoder motor and go with your original plan.

I'm into the wiring on my 6L80 right now but it may be several weeks before I can have more detail for you on this one. I was alternatively going to use the high voltage for the 4lo indicator light to pull a relay to trigger an input to my standalone to switch to shift table B, but this won't do you any good as you have to get the 4LO signal correct to the PCM.
 
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