Help with 4wd ADD system wiring

[twofiftyseven]

Hey everyone, I recently picked up another 3rd gen (99 sr5 4wd) and the previous owner did some work and ended up disconnecting the 4wd wiring system and cutting the wires that go to the ADD actuators. I was curious if someone could point me in the right direction in terms of rewiring it. The 4 wires cut from the vacuum actuators are supposed to go into the main wiring harness under the fuse box in the engine bay. I’m hoping that I can simply wire those 4 wires to something on the T case that will tell the actuators when to supply air to the front diff. Can anyone shed light on this? I have the standard J shift 4wd system so no multi mode.

The first 2 photos are of the cut wires. The third photo is of wiring connectors on the T case that im hoping wire to the actuators.

Please let me know if you need additional info/ photos. Thanks in advance!

 

[phattyduck]

The j-shift transfer case switches (well, the '4WD' switch) connects to the ADD relay in the passenger kick panel, from that relay, the wiring goes across the dash harness, then back out into the engine bay, below the fuse box to the VSVs. The relay is needed as part of that circuit for everything to work right.

Wire connections:
White-Black = ground
Green-Red = +12V in 2WD
Light Green = +12V in 4WD

I wonder why the previous owner didn't just pull the 4WD fuse?!?

-Charlie

 

[twofiftyseven]

@phattyduck Thank you

Thank you Charlie, this is exactly what I needed. Also curious why he didn't just take the fuse out. I took off the panel, but am not sure what I am looking at. I'm assuming the silver box is the 4wd computer, but as for the other wiring connectors, I'm a bit lost. Can you show me which connector to tap into? Also to confirm, the wires run under the fuse box in the engine bay, but not connected to it correct?

Thanks,
again.

 

[Bad Luck]

Thank you Charlie, this is exactly what I needed. Also curious why he didn't just take the fuse out. I took off the panel, but am not sure what I am looking at. I'm assuming the silver box is the 4wd computer, but as for the other wiring connectors, I'm a bit lost. Can you show me which connector to tap into? Also to confirm, the wires run under the fuse box in the engine bay, but not connected to it correct?

Thanks,
again.

Did the PO install tacoma hubs in the front?

 

[twofiftyseven]

Did the PO install tacoma hubs in the front?

I don't think so. They look the same as my other 3rd gen. If' you're asking about manual vs fixed, they're fixed, so when the wheels spin, the axles do too.

 

[Bad Luck]

I don't think so. They look the same as my other 3rd gen. If' you're asking about manual vs fixed, they're fixed, so when the wheels spin, the axles do too.

Well there goes my theory on cut wires...

 

[phattyduck]

Thank you Charlie, this is exactly what I needed. Also curious why he didn't just take the fuse out. I took off the panel, but am not sure what I am looking at. I'm assuming the silver box is the 4wd computer, but as for the other wiring connectors, I'm a bit lost. Can you show me which connector to tap into? Also to confirm, the wires run under the fuse box in the engine bay, but not connected to it correct?

Thanks,
again.

No, there is no 4WD computer... Just a relay. Right there near the top. Two Black-White wires, a Light Green wire, a Green-Red wire and a Blue wire. If it clicks when you shift in/out of 4WD (with key ON), then the transfer case portion of the wiring is working. The silver box is the ABS computer. If you did have a 4WD computer, it would be in the driver's kick panel area (only on Limiteds in '99).

If the wires were cut in the engine bay, why don't you just re-connect them?

-Charlie

 

[twofiftyseven]

No, there is no 4WD computer... Just a relay. Right there near the top. Two Black-White wires, a Light Green wire, a Green-Red wire and a Blue wire. If it clicks when you shift in/out of 4WD (with key ON), then the transfer case portion of the wiring is working. The silver box is the ABS computer. If you did have a 4WD computer, it would be in the driver's kick panel area (only on Limiteds in '99).

If the wires were cut in the engine bay, why don't you just re-connect them?

-Charlie

Hi Charlie,
I wish it were that simple. I've now realized he did a body swap(2wd body on a 4wd frame/drive train). The harness thats in the truck appears to be from a 2wd, so it doesnt have the add wiring/relay or 4wd wiring I dont think. I did happen to go by a junk yard yesterday and find an ADD relay. Do you think its possible to just wire the T case to the relay and then to the ADD actuators in the engine bay? If so, do you know which wires on the T case need to be tapped into? I havent been able to color match any of them unfortunately.

 

[phattyduck]

The plot thickens! Now we will need to know the year of the engine ecu and the dash wiring (could be different...), which effects wire colors, etc. You also need to track down of the 4WD harness was used on the engine/trans (likely, it *should* have stayed with the engine/trans during the body swap).

Just as a note, my 2WD SR5 body had all the dash wiring for the SR5 J-shift 4WD system, what was missing is a few wires in the engine harness and engine bay harness. I had to add two wires on the engine bay harness (the one that goes from the driver's kick panel up to the fuse box) and 3 wires on the engine harness (goes from ECU/behind glove compartment to engine/trans/transfer case). The dash had the ADD plug and wiring in place already, I just had to put in the relay.

-Charlie