Code C0388-04 says open circuit I checked to make sure I did not have a broken wire coming out of the rear differential and then checked the coil and the resistance was 3 ohms book say 2.4 - 4 is the range all the other 4 wheel drive functions work except the rear differential does not engage ,I have to check the wiring again ,once I started typing this I realized that the power and ground comes from the TCCM so I need to recheck it one wire at a time not the meter hooked up to both wires is the TCCM [Transfer case control module] that fails often on these ours is a 2008 so the 4 wheel drive selector is a know that you turn like on our suburban and the rear differential is a separate button which flashes when selected but it does not engage also the manual said I would need to reprogram the TCCM if it was replaced does anyone know what kind of scanner would work for that and if anyone has any suggestions Thx

 

did you enable it the way it says to in the owners manual? put transmission in neutral push 4 low then enable the locker? the truck is always in 4 wheel drive. if the rear diff is not working then you have a broken chain in the transfer case or you have a bad rear differential. but maybe it is just user error.

 

yes I did that and it does not engage I checked to coil in the rear differential which is what the 12 volts runs through to engage the rear differential and it rings good with 3.4 ohms so from that check that part seems good i either have another broken wire or the TCCM is bad the rest of the 4wheel drive system works normal I just did know if anyone on here had experience this before there is alot of knowledgeable people on here , but I am going to check out all the rest of the wiring before I order a part Thx foe the input any suggestions are helpful

 

if your talking about the rear diff locker then check the cables coming out of the diff for breaks / bad connection. rear lockers are only needed in critical situations not usually in every day driving.

 

Yeah that was the first place i checked then i checked continuity through those wires through the coil that is inside the rear differential and the coil checked good according to the manual I have a three volume GM service manual for these things so I am working on going through it now to see what I can check next Thx

 

next would be to test the pins at the other end of the wiring and see if you still have the resistance values you described there. if not then there is a break some where. i do not recall if the locker gets ground from a chassis ground on the left rear chassis body mount. but i am sure you can look that up in the manual.

 

so I ground the issue with the rear differential not locking in for some reason someone had cut the two wires going to the rear differential actuator or coil what ever you want to call it I had to start tracing wires and found the two wires cut and wired to this what appears to be a resistor or something and it had co.e apart and I guess that is when I started getting the 4 wheel service light coming on , i checked everything according to the book and all voltages are right and so i hooked the wires up just twisted together with i meter in line and checked agian everything was normal so i hooked everything up permanently and went and tried it out and everything works as advertised what baffles me is why would someone do this well I mean if everything works why would you need to do it does anyone have any ideas or has anyone ever seen something like this before Thanks for the feed back also thanks to the guy can't remember off the top of my head who it was but told me about the INNova code reader it works great .