4-HI conversion for TOD equipped Isuzus

By: RNEAL54715@aol.com

Warning: Performing this modification is to be done at your own risk. This will almost certainly void the warranty on your transfer-case, and potentially the rest of the drive drain. Proceed with caution.

Shopping List:
All items purchased for less than $25

Radio Shack Part Number	Description	Qty
2750731	4wd HIGH Switch. Soon to be replaced by the Isuzu 4WD switch from a Rodeo model	1
2750218	Relay	1
2701213	Fuse Holder	1
2701081	10 Amp Fuses	1
2710132	Two 10 OHM resistors	2
2701804	Project Box to fit the RELAY and two OHM RESISTORS in. Refered to as BLACK BOX	1

Borg Warned Schematic:
This is an image of the PDF file provided by the Chief Engineer at Borg Warner (Manufacturer of the TOD computer and the transfer case.) You can see that he has identified PIN11 on the back of the TOD unit, as the correct wire which sends power to the clutch solenoid. The engineer has confirmed that on 2000-2002 troopers with 48pin connectors that is the case. He also advised that on 1998 - 1999 troopers with a 30 pin connector at the TOD Control Unit it is PIN 4, not PIN 11.

NOTE: I strongly suggest you get a printout of the factory service manual for your exact vehicle to make absolutely sure you've got the correct wiring diagram info. On my 2002 trooper, Pin 11 from the TOD unit, converts to Pin 10 at the H33 connector - and it is a baby blue colored wire as you can see in the pictures.

THE TOD CONTROL UNIT DIAGRAM BELOW IS FOR 2000-2002 troopers, NOT 1998 or 1999.

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Improved Schematic:
Also attached is this improved schematic that my engineer friend created for this mod. See attached PDF for clarity

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Wiring Detail:
Please click on the following two diagrams to enlarge them:

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Installation Steps:
REMEMBER, THIS IS ON MY 2002 TROOPER. YOUR PINS, WIRING, and CONNECTOR NUMBERS AND LOCATIONS MAY BE DIFFERENT.

MAKE SURE VEHICLE IS TURNED OFF, KEY OUT OF THE IGNITION

The first thing to do is locate the H33 connector under the front passenger seat. Remove the plastic side cover and you will see what I see. The H33 connector is tucked under a piece of carpet. It is protected by a black plastic rubber boot. The connector passes through the floor of the vehicle, and out the bottom of the vehicle. Sorry for this picture being improperly oriented. You will want to push this connector back up into the vehicle, and detach the two parts. NOTE: PIN 11 from the TOD control unit connects to this H33 connector at PIN 10. ON my car it is a blue wire. Your will need to remove the blue wire from each of the connector ends. IT IS BELIEVED THAT THE TOD CONTROL UNIT POWER OUTPUT TO THE CLUTCH IS Pin 11 on 48 pin connectors (2000-2002), AND Pin 4 on 30 pin connectors (98-99). REMEMBER, THESE PIN LOCATIONS REFER TO THE LOCATION AT THE CONTROL UNIT ITSELF, NOT AT THE H33 CONNECTOR. MAKE SURE YOU GET IT RIGHT FOR YOUR VEHICLE.

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Here are the tools I used to disconnect the wires from the connector. You can simply cut the blue wire if you want to - but I didn't want to cut the OEM wires. The piece on the left is a standard picture holder that you would nail to a wall. I used two of these picture holders to create the two tools on the right. I bent them flat, then I used a grinder to shave down the sides to make them narrower. I needed two, as you will see in a moment.

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Here is a close up of the two strips I made.

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Now, I will describe how I removed the blue wires from the MALE END of the H33 connector. In this picture I had already removed the wire, but see where I drew in a blue line to simulate the wire. Insert one of the metal strips into a slot beneath the blue wire. Note: This is PIN 10 at the H33 connector. Then push the metal strip all the way into the connector in order to force the plastic catch down. Continue to next picture

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Now, this is the front view of that same male connector. You should already have one of the metal strips inserted into the back of this connector at the blue wire. Now, you must insert the other metal strip into the face of the connector at the same terminal. This second metal strip is to hold down the plastic clip, that the first metal strip dislocated. Once this metal strip is inserted, the first metal strip can be removed, and the blue wire can be pulled out from the back side.

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Now, with both metal strips in place, remove the original metal strip from the back side. Then, pull the blue wire out of the connector. Be very careful. If you do not remove this first metal strip the blue wire is in too much of a bind to be removed. And you need the second metal strip to hold it from the other side, so the first strip can be removed. I hope this isn't too confusing - but this is what I learned from over 1 hour of messing with the wires.

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This is what the end of the blue wire looks like once you remove it from the male end of the H33 connector.

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Now, you must remove the blue wire from the FEMALE end of the H33 Connector. This is much easier to do… but you still need to modify one small screwdrive head.

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This is a closeup of the flathead screwdriver head that I had to grind down to fit insider of the female connector.

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Insert the modified tool into the female H33 connector and disengage the plastic keeper. Then simply push the metal tab out with a pair of pliers.

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This is what you will have once you have successfully removed both ends of the blue wire from the H33 connector. Don't pay any attention to the string that you are seeing in some of the pictures. I used the string to "lasso" the connector and help hold it up from sinking into the floor of the vehicle.

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Now, you can re-connect the H33 connector, and re-connect the blue wires independently of the connector. In this mode, your system is just as it was, except the blue connection is made outside of the H33 connector. TOD operates as designed. NOTE!!!!! THIS IS A GOOD STOPPING POINT - while you are waiting to get your other parts on the shopping list. IF YOU LEAVE IT THIS WAY, BE SURE TO PROPERLY tape the blue wire connectors with electrical tape so they don't short out to the frame. Remember, these blue wires carry the 12volt current to the Clutch, so don't let them short out.

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Now, lets focus on the relay bypass. The details on how to wire this are on the attached sheets IMPROVED SCHEMATIC and WIRING DETAILs. The Black box houses the relay and the two OHM resistors - one on top of the other. You can see I placed a US Quarter on the box to give you some reference on size.

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Here is another view of what is in the black box. You can see that the two OHM resistors are wired together in SERIES, not parallel. Don't be fooled by the image.

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The box has 4 wires coming from it. BLACK = ground, RED = 12v Power, BLUE = to Clutch, WHITE = to TOD Control Unit. This box will be placed under the front passenger seat, grounded at that location, all connections made, and our separate source of power will be brought to it. BE SURE TO KEEP YOUR COLORS STRAIGHT. THe black box has a blue wire, but this is a different reference than the blue wires from the H33 Connector.

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I decided to get power from the back of the accessory jack location as it is close to the front passenge seat.

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Remove the 4 screws that hold the console in place, and put your vehicle in drive. Putting the vehicle in drives gives you the clearance around the shift lever to be able to raise the console up a bit so you can reach behind it. Remove the orange and black connector from the back of the accessory jack

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Splice onto the hot line (orange wire in my case) in to get 12 volt power. You can see I am attaching the fuse at this location

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When those connections are made, replace the console. Note: The fuse can be neatly tucked behind the console panel and accesses whenever you need to check the fuse - you don't have to remove the console again in order to check the fuse, simply pull it out and tuck it back in.

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Finish wiring the new switch around this same location. Note: This is a temporary switch and location. As soon as I order at DASH SWITCH to install next to the TOD AUTO switch I am going to move this switch location.. Attach the input power, the ground line and the output power to the switch. See switch wiring detail on the attached sheet. NOTE: I grounded this switch to the lower left hinge on the glove box - it was a close and convenient location. The switch has a light on it to illuminate when on, FYI.

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You now need to run the power from the switch, behind/around the glove box, and down the side of the car to the intended location. You need to remove the plastic step plate to run the power line under it. You can then connect the power line from the switch, to the red wire from the black box.

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Now, you need to attach the black box to ground. I didn't want to drill any holes in the vehicle, so I chose this location. Once you remvove the plastic step plate above, you will see this grey wire holder attached to the green seat bracket (MY trooper is Green). Remove the grey plug and just let that wire lay in that position.

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Next, I used a small grinding tool to grind an area of the paint away so I would have a good ground contact.

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Next, I attached the black wire from the black box, to this location for ground.

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Next, you should test to make sure the installation is OK to this point. Be sure the white and blue wires from the black box aren't touching anything. TURN THE KEY TO THE ON POSITION, Turn the new Switch to the ON position. The Switch should light up indicating that it is grounded properly. NExt, check the BLUE wire from the black box to make sure it is outputting 12volts. CHeck it to any ground point. Then, when you turn the new switch OFF, the BLUE wire from the black box should be dead. If everything looks good, you are ready for the last two connections. TURN YOUR IGNITION BACK OFF AND REMOVE THE KEY FROM THE IGNITION.

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More explanation on these connectors… The white wire goes to the TOD computer. It is attached to the end of the Baby Blue wire that runs to the TOD control unit. Note, this end of the baby blue wire has a small metal female connector, so accordingly the white wire from the black box has a modified connector on it (like a stake or knife blade) see below illustrations. The reverse is true for the blue wire from the Black box.

It is somewhat confusing to describe in text, I think you'll be OK when you see the parts.

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This is a picture ot the Blue wire from the BLACK BOX being connected to the baby blue wire running through the bottom of the vehicle to the clutch.

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This is a picture of the white wire from the black box being connected to the baby blue wire leading to the TOD control unit. Note, the blue wire from the black box is also connected. Again, be sure to TAPE both of these connections so they don't short to anything

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That's it!!!! The red wire you see is extra power line coming from the accessory jack. You can see the black box sitting on the carpet under the seat.

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Put both of the plastic pieces back on

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Good luck to all of you. Remember, the vehicle must be in 4wd AUTO mode (to lock the front axle) before you turn the new switch ON (to send power to the clutch). The green lights on the TOD indicator panel will still work for TOD mode. And, they will also display TOD signals when you are in 4wd HIGH LOCK mode. The only way you will know that you are in 4wd High Lock is the light on our new switch, and the powerful feel in the drive train. Test Results
I tested the vehicle for over 3 hours last weekend (10/12/03). The vehicle performed flawlessly.

At one point I had the POWER MOD engaged for over one hour of continuous use - again, absolutely no problems.

There are a couple of handling/operation characteristics that you need to be aware of:

As with any 4x4 system, there is considerable spring tension that builds up in the drivetrain components due to turning and braking (which causes wheels to turn at different speeds and creating binding or spring tension.) And, this tension must be released in some manner once it builds up to a point. Either 1) the tires will slip on soft surfaces, or 2) because the TOD system uses a clutch plate, and not a mechanical gear, the clutch can slip under all of the pressure and you will hear the "clunk" sound every now and then, only when your making tighter turns, and on a harder dirt surface that won't allow the tires to slip to release the tension. If you are on very slippery mud or soft dirt, the tires are free enough to spin and release the tension without the clunk - only on harder surfaces will you hear the clunk. And, if you are in fact on a hard surface, you wouldn't need to be in POWER MOD anyway - so it is really a minimal issue.

I also observed in POWER MOD, that if you come to a complete stop, then turn OFF the POWER MOD, it will CLUNK (sometimes, depending on the amount of spring tension). If you are rolling when POWER MOD is turned OFF there is no CLUNK.

I noticed that when in PowerMod I did see the green lights flashing on the front tires - especially when I stomped on the gas on gravel. It is believed that TOD responds to both SLIP and THROTTLE POSITION. So, in that instance, it was probably responding to throttle and that the clutch was likely not slipping. FYI.. So, If you see green lights peeking on the front tires when in PowerMod mode - don't worry about it.

Remember to FIRST ENGAGE THE 4wd AUTO button, before engaging the POWER MOD. I'm not altogether sure if the reverse causes any problem, this is just the logical sequence to first have TOD lock the front axle, before POWER MOD locks the transfer case. Plus, the Engineer said to do it this way. When I re-wire the switch to the dash, I am going to consider having the 4wd Auto switch trigger another relay to activate the alternate power source - that way the POWER MOD would not turn on without the 4wd AUTO switch being turned on first.

Referencing the above point… I have created an additional mod to address the issue of switch sequencing. Please see the additional section called SWITCH SEQUENCE CHANGE below.

Comparison:
I thought it would be beneficial to compare and contrast the two known mods. The original SENSOR MOD, and what I developed called the POWER MOD.

Note: The credits for the POWER MOD go to the folks on ITOG, BorgWarner, my Engineer friend, and of course ME.

SENSOR MOD:
Cut the wire from the front sensor. Tricks TOD into thinking that the rear tires are slipping, and therefore sends power to the clutch to lock 50/50 split

Most people simply CUT the oem wires - but you can go through the effort of removing the wires from the H33 connector so that the mod can be removed without a trace.

Easiest to install.

Error codes generated

SENSOR MOD results in vehicle clunking in and out of 50/50 lock whenever you come to a complete stop. The reason is that when you are stoped, the TOD computer has the same ZERO reading from the front and rear driveshafts - this tells the computer that the tires aren't slipping so it stops sending power to the clutch and the 50/50 split disengages. When you begin to move forward again, TOD senses movement in the rear driveshaft, and no movement in the front (because the sensor line is cut) so it again re-engages the clutch and the 50/50 split. Hence, all of the clunking sounds.

I believe SENSOR MOD will still DISENGAGE (stop sending power to the clutch) when the wheels are turned at a sharp angle. Remember, the logic designed into TOD is to release the clutch when the wheels are turned at a sharp angle to prevent the BRAKING EFFECT. What this means is you will have no front wheel power if you are trying to make a sharp turn on ice, snow, or any other slippery surface.

POWER MOD:
Independent source of power is sent directly to clutch to lock 50/50 split. The TOD Power is diverted to a DUMMY LOAD OHM RESISTOR and has no resulting effect.

As described in this file, the POWER MOD is designed to be easily removed without a trace. No modifications to any of the oem components. And therfore no warranty implactions

A bit more time intensive to wire up the relays, resistors, etc. But I believe well worth the trouble.

No error codes

POWER MOD is perfect. It sends continuous power to the clutch whether you are stopped or moving. The only time you will hear a CLUNK is when you are on a harder surface where the tires cannot slip to release the spring tension - then you will hear a clunk sound as the clutch itself slips. Note: SENSOR MOD would also slip and clunk in this manner.

POWER MOD is perfect. I sends continuous power whether you're going straight or turning at sharp angles.

Remember - do your homework to make sure this mod will work on your trooper. And you should triple check my work in case I made a typo in these instructions. I think the replacement computers are over $1500 - so BE EXTRA CAREFUL!!!!!

I strongly suggest that you obtain the schematics for your exact model TOD. This is just to be extra cautious.

You could ask your local dealer to print out the schematic for you from their CD version of the FACTORY SERVICE MANUAL for the TOD component.

Switch Sequence Change:
Recall that TOD AUTO should first be activated in order to lock the front axle BEFORE YOU ACTIVATE POWER MOD. If you are stopped, or traveling when the drive shaft is at the same speed as the wheels (meaning no slipping) then it really isn't an issue. However, if you encountered a condition where you were getting stuck in the mud and your back tires were spinning fast, while your front axle was spinning slowly if at all - then you had PowerMod ON first, the front driveshaft would be spinning very fast too. Then, if you attemped to turn TOD AUTO ON, you would be attempting to lock a slow moving wheel with a fast moving driveshaft - and there is the possibility of additional wear to the axle locks. This is such a very rare instance... but it is foreseable, expecially if you have others operating the trooper and dont remember the sequence. So, one of you was very persistent in asking me to develop a wiring schematic that takes the guess work out of it... and we have done that.

Essentially, we decided to use the AXLE LOCK switch as an indicator that the TOD AUTO had locked the Axles before powermod would receive any power. So, regardless of whether PM was ON or OFF, it wouldn't get power unless the Axles were in fact locked.

It is another simple wiring job, but it will take a bit more work, one new relay, a diode, and another small work box.

It also requires that you CUT one of the OEM wires from near the fuse box. In the original design I went to great trouble not to have to cut any wires at the H33 connector - However, I couldn't remove the wires from the connector like I did at H33 because the connector is almost impossible to get to without removing the entire dash and fuse box. So I chose to cut the wire.

Also, in the SSMA I also installed the ISUZU oem switch that was used in the Rodeos. It is available from Merlin at the MO Isuzu dealership advertised on ITOG.

Parts: