'98 Limited: swap push button 4WD transfer case for 98 SR5 j-shifter tcase & ADD

[farmerjon]

'98 Limited: swap push button 4WD transfer case for 98 SR5 j-shifter tcase & ADD. Starting a new thread from the original engine thread, as I would like this to be a reference for those in this situation.

98 SR5 Engine into a Limited Chassis - which wiring harness/ECU to use?

I swapped my 98 SR5 engine/transmission/transfer case into a 98 Limited. Everything works, including cruise control, but not the 4WD:

1. 4WD worked on the Limited before the swap.
2. SR5 wiring harness kept with the SR5 engine and transmission, everything hooked up fine.
3. 12v at the VSVs, does not switch when throwing the jshifter into 4WD, key on.
4. ADD does not click when throwing the jshift forward, key on, VSVs unplugged.
5. Switching vacuum hoses engages front diff and the light comes on the dash, with the jshift engaged, and the front driveshaft locks.
6. 4WD ECU replaced with SR5 ADD relay - see pictures for wiring diagram of SR5 vs Limited, as well as current wiring setup on the ADD relay.
7. single black/yellow wire from 4WD ECU is wired into 3 way solder with the 2 black/yellow from SR5 ADD relay. No 12v power with key on. Currently, it seems I should jump the 4WD fuse under the dash and wire it to the black/yellow from the SR5 ADD? is it true there's no 12v power from the black/yellow 4WD ECU wire unless the ECU is there? I probed all of the wires on the 4WD ECU harness and no power on any of them in 12v with key on.
8. the other option is to switch the pink/green wire with the green/pink? one is the position sensor and one is the 4WD power, I think.

Appreciate any advice or perspective I can get.

 

[phattyduck]

The Black-Yellow wire should always have power with key-on. Fix that issue first. The 4WD ECU should be removed if you are running the ADD relay.

The Green-Red wire should go to the non-powered side of the ADD relay, same connection as the 4WD ECU used. But, the wiring between the dash and engine harness may be different on the SR5 compared to Limited - make sure that is actually on the same pins at the dash to engine harness location.

Connections to the ADD VSVs should match between the 4WD ECU and ADD Relay version - just match colors to their new connection on the relay.

-Charlie

 

[TheDurk]

The Black-Yellow wire should always have power with key-on. Fix that issue first. The 4WD ECU should be removed if you are running the ADD relay.

The Green-Red wire should go to the non-powered side of the ADD relay, same connection as the 4WD ECU used. But, the wiring between the dash and engine harness may be different on the SR5 compared to Limited - make sure that is actually on the same pins at the dash to engine harness location.

Connections to the ADD VSVs should match between the 4WD ECU and ADD Relay version - just match colors to their new connection on the relay.

-Charlie

I just had to fight the non-responsive ADD relay issue on mine. I was about to source a replacement but hard to find and I actually bought a five-pin Bosch-type relay and socket to sub in just as Charlie suggests here. I decided to try a little surgery on the relay first and it was a surprisingly easy fix. Contacts were all corroded up and a little superfine sand paper and contact cleaner and that puppy is working like new. Not the case here, because OP has no original ADD relay, but I post this for anyone searching on the subject. Give it a try. It comes apart by prying the can up from the plastic base. Don't try un twisting the little pins that come through the base; those are what attach the relay mechanism to the base. Just pry off the can.