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Virtual Technician
Virtual Technician, ASE Certified Technician
Category: Car
Satisfied Customers: 96
Experience:  25 years Experience. All makes and models, Shop Owner, Access to 4 repair databases. - I take the Opt Out Questions :)
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Isuzu Trooper: 2001 Isuzu Trooper with automatic Torque on

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2001 Isuzu Trooper with automatic Torque on Demand 4 x 4. I had the transmission rebuilt and now the TOD 4 x 4 lights flash constantly with a light below saying CHECK. The dash button for automatic 4 x 4 does not engage the front differential, the lever on the floor for low works. When you stop the lever in the neutral position the lighs stop flashing. We are not getting current from the dash switch down to the electric over vacum swithces on the front differential. when we ran a jumper wire fron the dash switch down to the diff switches the 4 x 4 worked with the dash switch but the lights kept flashing. HELP, William

Virtual Technician :

Hello, My name is XXXXX XXXXX I will try my best to help you with your vehicle issue.

Virtual Technician :

Do you have a code 28?


I am in the country of Panama and computers to read trans has not been found so no way to know codes


I am told that a shop near my village has such a computer but they are not sure how to read it. Monday when they open I will visit and see if they can read the codes if any show up. I am using an internet cafe machine so am not on line all the time, will check in Monday in the afternoon with info on what I find. W

Alright, that makes it quite a bit tougher but let's see what we can do.

Please note: Not every answer I give you is something you were hoping to hear, even though it is true.
Such as; (it's more expensive than you wanted to spend, or you will need to have a professional repair shop do the diagnostics and /or repairs due to complexity reasons).

1. Check for broken vacuum lines in the TOD system.

2. Check for vacuum to the Front Axle Vacuum Solenoids.

3. Check for battery voltage to the Front Axle Vacuum Solenoids on the Blue/Yellow wire in 2WD and no voltage (near 0 volts) in TOD 4WD.

4. Check the Front Axle Switch for 12 volts in 2WD and no voltage (near 0 volts) in TOD 4WD when the front axle is engaged.
Tech Tips: There are two Front Axle Vacuum Solenoids (on the center of the front axle) that are controlled by the TOD Control unit (below the right front seat) to control vacuum to the front axle diaphragm to engage the front axle. There is a Front Axle Switch on the left center of the front axle that tells the TOD control unit that the front axle is engaged. The Front Axle Vacuum Solenoids are wired in parallel.
Virtual Technician and 4 other Car Specialists are ready to help you
Please let me know what you find on these
Customer: replied 4 years ago.

Hola, I checked the vacum lines and found that a line from the engine has vacum into each of the vacum seolenoids, the right side of the blue and the left side of the white. Vacum from the center of the çenter of the white to the piston control but not from the center of the blue one to the other tip on the piston control. No vacun on the left of blue and none on the right of the white, these 2 lines go up to the drivers fender well and attach to a small vent. The 2 lines that have vacum also go back to a small tank on the frame under the drivers door. We have 12 volts to the front axle 4WD automatic switch on the dash but none to the front axle vacum Solenoids. Does this current by chance go thru the TOD Control under the passangers seat.? ?the drive shaft from the transfer case to the fromt axle turns all the time when driving even in 2WD, is this supposed to be that way? We did not have this blinking light problem before we removed the transmission to rebuild it for the hard shift from 1 to 2 and 2 to 3. When they installed it rebuilt the lights started blinking. When the 4 x 4 floor lever is in 2WD the lights blink, when it is in the neutral position it goes out. When it is forward in the 4L position they blink and the car is in 4 x 4. Sorry for all the ? but being in a 3rd world country is difficult to get repairs.

Have you checked to make sure no electrical or vacuum lines were pinched or damaged when replacing the transmission?
Customer: replied 4 years ago.

All the vac lines I can see are open, I guess I need to go back to the shop and have them drop the guards and cross menbers so we can look for electricl wires in that area. It seems strange to me that the lihgts go out when we put the 4 x 4 floor shift lever in the neutral position, maybe there are some electrical wires inside the transfer case ? Are you aware of any inside the transfer case ?

Here's the wiring diagrams for the transfer case - they are kind of spread out as this is the way Isuzu makes their diagrams.

The module is the tricky part that would take an ISUZU factory tool to check inputs & outputs from.


Good morning,

Just following up to see how the inspection went.

Have a great day,


Customer: replied 4 years ago.

We have been in Mardi Gras Carnival mode for the past ten days, no work as all the mechanics stay drunk. Yesterday we put the car on the pit and in 5 mins he found a pinched wire that was the result of not paying attention when they installed the rebuilt job. All works ok now, thanks for your help, I will arrange to release the payment to you. W

That's great - I'm glad that we were on the right track and that it was an easy fix.

Have a great weekend!