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

farmerjon · Apr 16, 2025

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

Both trucks are 1998. The SR5 engine/transmission/transfer case (jshift) are being moved to a 1998 Limited Chassis. Should I move over the wiring harness and keep the SR5 wiring harness and ECU with the engine, or will I run into issues?

I understand from my other thread about the transfer case that there is a different wiring plug needed for the transfer case, but that depends on which wiring harness I use?

Thanks for any insights!

phattyduck · Apr 16, 2025

Use the engine/transmission harness that matches the transfer case and vehicle wiring. The engine stuff is the same, but the transfer case sensors/wiring are different and run through the engine/transmission harness.

Since the engines are the same year, all engine related stuff will be plug-n-play. You will have to remove the intake manifold to swap harnesses, but it is easy after that.

-Charlie

farmerjon · Apr 16, 2025

phattyduck said:
Use the engine/transmission harness that matches the transfer case and vehicle wiring. The engine stuff is the same, but the transfer case sensors/wiring are different and run through the engine/transmission harness.

Since the engines are the same year, all engine related stuff will be plug-n-play. You will have to remove the intake manifold to swap harnesses, but it is easy after that.

-Charlie

Thanks Charlie.

Should I attempt to swap the ECU behind the glove box as well, or will that have dash complications with the lighting, etc?

phattyduck · Apr 16, 2025

farmerjon said:
Thanks Charlie.

Should I attempt to swap the ECU behind the glove box as well, or will that have dash complications with the lighting, etc?

Why would you swap the ECU? You are putting a matching engine into the vehicle.

(oh, missed that you want to swap to the j-shift along with this...)

Why not keep the push-button case if its working?

The engine ECU has no control over the 4WD system and the indicator signals it receives (4WD and 4LO) the same no matter the transfer case configuration.

-Charlie

farmerjon · Apr 16, 2025

phattyduck said:
Why would you swap the ECU? You are putting a matching engine into the vehicle.

(oh, missed that you want to swap to the j-shift along with this...)

Why not keep the push-button case if its working?

The engine ECU has no control over the 4WD system and the indicator signals it receives (4WD and 4LO) the same no matter the transfer case configuration.

-Charlie

the Limited chassis has 333k and the shifting didn't go well the last time I tested the transfer case, so I figured it would be simpler to have the jshift. I also have 145k mile history on the transfer case/transmission/engine, so am attempting to keep it all together.

I think a 4WD ECU has been mentioned as well in the driver's kick panel, so I might be able to leave that unplugged.

Sounds like best case is to keep the SR5 harness with the SR5 engine/transfer case. hopefully I don't get all the way done and regret it.

phattyduck · Apr 16, 2025

farmerjon said:
Sounds like best case is to keep the SR5 harness with the SR5 engine/transfer case. hopefully I don't get all the way done and regret it.

You can always compare the two dash connectors on each (between the engine harness and dash, they clip to the top panel of the glove compartment). Make sure all the wires are in the same locations with the same colors...

-Charlie

T4R2014 · Apr 17, 2025

I'd swap the SR5 harness into the Limited. What happened to the SR5?

St Runner · Apr 17, 2025

I agree, the best way to do it is use the engine harness and ecu for the SR5. Your dash harness is going to be different and you will have some small issues. Your 4wd lights wont work. Is your ABS the same? It will run fine, just going to be some work to get those small details back to factory. Or you can just ignore them like I did when i put a j-shift in my 2001

phattyduck · Apr 17, 2025

St Runner said:
I agree, the best way to do it is use the engine harness and ecu for the SR5. Your dash harness is going to be different and you will have some small issues. Your 4wd lights wont work. Is your ABS the same? It will run fine, just going to be some work to get those small details back to factory. Or you can just ignore them like I did when i put a j-shift in my 2001

Keep in mind the early ('96-'98) Limited case is just a push-button case, no multi-mode. It is a lot closer to a J-shift (length, etc.) than the later multi-mode case. Single light on the cluster for 4WD indication, too.

-Charlie

farmerjon · Apr 18, 2025

phattyduck said:
You can always compare the two dash connectors on each (between the engine harness and dash, they clip to the top panel of the glove compartment). Make sure all the wires are in the same locations with the same colors...

-Charlie

Thanks for the info on comparing the wiring colors/pins - this is a great idea. Hopefully easy enough to get my light working. I am deaf so I already have a hard time telling if in 4WD or not unless I'm turning or suffering from traction issues.

T4R2014 said:
I'd swap the SR5 harness into the Limited. What happened to the SR5?

Thanks! Going to keep the SR5 harness with the SR5 engine and t-case. SR5 rusted out - this is the one in my signature I've had for 12 years/145k miles. Been wanting to swap engines into a cleaner frame for years, so finally found another white 98. Will need to post pictures. Timmy the Toolman has been an invaluable resource.

St Runner said:
I agree, the best way to do it is use the engine harness and ecu for the SR5. Your dash harness is going to be different and you will have some small issues. Your 4wd lights wont work. Is your ABS the same? It will run fine, just going to be some work to get those small details back to factory. Or you can just ignore them like I did when i put a j-shift in my 2001

I assume ABS has to be the same, both trucks being a '98. 4WD light won't work even with the ECU and harness moved over - because of the ADD vs 4WD kickpanel ECU differences? I suppose I'll need to find a way to initiate the ADD aspect - maybe bring over those vacuum valves in the fender from the SR5?

Thanks all!

phattyduck · Apr 21, 2025

farmerjon said:
I assume ABS has to be the same, both trucks being a '98. 4WD light won't work even with the ECU and harness moved over - because of the ADD vs 4WD kickpanel ECU differences? I suppose I'll need to find a way to initiate the ADD aspect - maybe bring over those vacuum valves in the fender from the SR5?

Thanks all!

Only the ADD position switch is on the engine harness (and is the same between the two transfer case styles). ADD VSV plugs are NOT in the engine/trans harness. The ADD VSV plugs come off of the main harness that runs on the driver's side fender.

-Charlie

farmerjon · Apr 21, 2025

phattyduck said:
Only the ADD position switch is on the engine harness (and is the same between the two transfer case styles). ADD VSV plugs are NOT in the engine/trans harness. The ADD VSV plugs come off of the main harness that runs on the driver's side fender.

-Charlie

Leaving the engine/transmission harness attached to the SR5 engine, so it will come over to the Limited. Sounds like i need to find the main harness as well - do I swap that over, or just part of the harness that has the plugs?

phattyduck · Apr 21, 2025

farmerjon said:
Leaving the engine/transmission harness attached to the SR5 engine, so it will come over to the Limited. Sounds like i need to find the main harness as well - do I swap that over, or just part of the harness that has the plugs?

No, the plugs are the same. The VSVs on both the SR5 and Limited are the same.

Speaking of which, make sure you unplug the ADD position switch when you remove the motor - it is VERY easy to miss underneath the driver's side exhaust manifold (accessed from the bottom rear, reaching in from behind the steering rack). The starting/charging harness also needs to be separately removed from the engine or unplugged at the fuse box/fender.

-Charlie

farmerjon · Apr 21, 2025

phattyduck said:
No, the plugs are the same. The VSVs on both the SR5 and Limited are the same.

Speaking of which, make sure you unplug the ADD position switch when you remove the motor - it is VERY easy to miss underneath the driver's side exhaust manifold (accessed from the bottom rear, reaching in from behind the steering rack). The starting/charging harness also needs to be separately removed from the engine or unplugged at the fuse box/fender.

-Charlie

Thanks Charlie. I hopefully got it already on the Limited motor removal, following Timmy the Toolman's guide - as I removed the transmission first, and then the motor, and didn't seem to find any torn wires, but I should check again.

The starting/charging harness is separate? does that live in the fender? the fusebox has a connection to the engine, but I separated that per Timmy's instructions.

Hopefully I can coordinate all these different things to remember.

phattyduck · Apr 21, 2025

farmerjon said:
The starting/charging harness is separate? does that live in the fender? the fusebox has a connection to the engine, but I separated that per Timmy's instructions.

Hopefully I can coordinate all these different things to remember.

Yes, it goes from the fuse box, down past the alternator, across the bottom front of the motor (in the white-ish cover) over to the starter. If you pulled a motor, you got it disconnected. It does not connect to the engine harness that actually runs the motor. That will be the same between the SR5 and Limited, 2WD, 4WD and even auto/manual - as long as the engine and the year match.

-Charlie

farmerjon · Jul 23, 2025

Update:

SR5 Engine/transmission/j-shift transfer case swap went well and engine is running and shifting fine in the Limited. The j shifter works physically and I think it shifts to 4WD, but with no light and my hearing loss, I'm not sure how to tell, aside from trying to do a donut in my neighbors yard.

What do I need to swap over from the SR5 chassis to get the dash light to work since I rely on that?

phattyduck · Jul 23, 2025

farmerjon said:
What do I need to swap over from the SR5 chassis to get the dash light to work since I rely on that?

Might be worth confirming what you are using for harnesses...

It is easy to figure out if 4WD is active - just make any turn on a hard surface. it will bind up pretty bad in 4WD and not at all in 2WD.

farmerjon · Jul 23, 2025

phattyduck said:
Might be worth confirming what you are using for harnesses...

It is easy to figure out if 4WD is active - just make any turn on a hard surface. it will bind up pretty bad in 4WD and not at all in 2WD.

Great question - thanks Charlie for pointing that out.

1998 Limited chassis
1998 SR5 engine
1998 SR5 harness
1998 SR5 transfer case (j-shift)
1998 SR5 ECU computer behind glove box.

Adventure Taco has an image with the various transfer cases - and it would seem that the sensors are different - and if I had used the Limited harness, I would have had a female plug for the 4WD sensor to use, perhaps. Most people who do this swap just do the transfer case into a Limited, which is actually kind of simple.

Since I've done SR5 everything, I think I need to find the link from the computer ECU to the dash, and then the light would work?

Step-by-Step Replacing the Transfer Case on a Tacoma – AdventureTaco

clearock · Jul 23, 2025

You need to know which cluster you have and then use a wiring diagram to determine which pins triggers the 4wd display on that specific cluster (or if you even have said). There are different clusters between the SR5, Limited, and limited with AWD. Repin/wire to get what displays you want to light up. There are some fuel gauges that have the 4x4 symbol that you can use to add the 4x4 symbol to an AWD cluster, etc. An understanding of wiring and how to make what you want to light up with what ever you are adding helps. No disrespect meant, with you original question this could be out of your ability or will at least take to a lot to time and effort.

farmerjon · Jul 23, 2025

clearock said:
You need to know which cluster you have and then use a wiring diagram to determine which pins triggers the 4wd display on that specific cluster (or if you even have said). There are different clusters between the SR5, Limited, and limited with AWD. Repin/wire to get what displays you want to light up. There are some fuel gauges that have the 4x4 symbol that you can use to add the 4x4 symbol to an AWD cluster, etc. An understanding of wiring and how to make what you want to light up with what ever you are adding helps. No disrespect meant, with you original question this could be out of your ability or will at least take to a lot to time and effort.

Thanks! Yes, wiring is a bit out of my depth. I edited my last post to include that both trucks are 1998 SR5, 1998 Limited, so the clusters should be the same. I can also swap the clusters if that would be easier. I will test 4WD and see if it is engaging

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

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