Question about Isuzu Trooper

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THE AUTO SWITCH FOR THE 4X4 ACTIVATES THE TRANSFER CASE WILE DRIVING ON ITS OWN. WHERE DO I LOOK FOR THE PROBLEM?

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  • wkays Jan 24, 2009

    Same problem on a 2002 Isuzu Trooper, just had the tranny rebuilt, then at 40MPH or faster, when coasting (foot off the gas pedal) the 4WD kicks in full 4WD no matter if TOD auto on or not.  Tranny shop cannot figure it out.  Help!

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Have a look at the breather on the transfer case, I had a symilar problem with my vehicle that the diff lock comes on while driving and it was the breather that were blocked, causing some sort of pressure or vacuum inside the diff that activated the diff lock. Just try

Posted on Jan 14, 2009

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2003 ford f250 superduty 4x4 don't work no indicator light on dash changed4x4 switch module what next?


Check for codes. Usually part stores do it for free. here is how it works.
Principles of Operation

Electronic Shift on the Fly (ESOF) System

The electronic shift on the fly (ESOF) system is an electronic shift system that allows the operator to choose between 2 different 4x4 modes as well as 2-wheel drive. The operator can switch between 2H and 4H mode at speeds up to 88 km/h (55 mph). To engage or disengage 4L, the 4x4 generic electronic module (GEM) requires that the vehicle speed be less than 5 km/h (3 mph), the brake pedal depressed and the transmission in NEUTRAL (or clutch pedal applied on manual transmission vehicles). This system contains pulse vacuum hublocks (PVH). The selector on the hublock, when turned fully counterclockwise to the AUTO position, engages/disengages the hub depending on the driver-selected 4x4 mode of operation. The hublocks also contain a manual override. When the selector is rotated fully clockwise to the LOCK position, the 4x4 vacuum and electronic system used for coupling the front axle to the wheel is bypassed.

The transfer case is equipped with a dual-cone synchronous clutch. This clutch is used to synchronize the front driveline to the rear. All other internals operate in the same manner as the manual shift system. When the mode select switch (MSS) on the instrument panel is turned, the 4x4 module powers the transfer case motor, which activates a shift fork and engages the clutch. When the shift motor reaches the desired position, as determined by the encoder position inputs to the 4x4 module, power to the shift motor is removed. When the transfer case front and rear output shafts are synchronized, the lockup collar mechanically engages the mainshaft hub to the drive sprocket. At this point, the front axle PVHs are engaged. Instrument cluster "4x4" and "Low Range" indicator operation is controlled via hardwired outputs from the 4x4 module.

Electronic Shift Transfer Case

The New Venture Gear NV 273 electronic shift transfer case is a 3-piece aluminium design. The unit transfers engine power from the transmission to the front and rear axles. Under normal driving conditions the unit is in 2-wheel drive high (2H), but when desired, the operator may shift into 4-wheel drive high (4H) or 4-wheel drive low (4L). The transfer case is shifted electronically. The unit is lubricated by a positive displacement fluid pump that channels fluid flow through holes in the mainshaft.

The encoder assembly used for mode indication is of a Hall-Effect type. The system uses a total of 4 independent transistors for mode recognition. Each transistor is associated with a specific range of motor movement. When the circuit to each transistor is closed, a ground path to any of the A, B, C or D encoder pins is accomplished. When the circuit to each transistor is open, the connection to any of the A, B, C, or D encoder pins is pulled to voltage. Mode indication is "decoded" by the 4x4 module based on the varying combinations of signals coming from the transistors.

Hublock Operation

With the hublocks in the Auto position, the 4x4 ESOP system uses timed vacuum sequences to lock and unlock the wheel ends when switching the instrument panel MSS between 2WD and 4x4 modes. A high vacuum level (222 mm or 8.75 in. Hg and greater) is applied to the hublocks to lock the internal spring mechanism that engages (locks) the hublocks for 4x4 mode, and a lower vacuum level (114 to 184 mm or 5.9 to 7.1 in. Hg) is applied to unlock the spring mechanism that disengages (unlocks) the hublocks for 2WD mode. The vacuum signals are supplied to the hublocks by system components, including the 4WD control module or GEM, wiring harness, solenoid, vacuum harness and vacuum seals. As a first step in service, eliminate obvious items such as loose wiring connections, loose vacuum connections or damaged vacuum lines.

Dec 12, 2014 | 2003 Ford F250

1 Answer

Where are the fuses for the 4x4 located on a 05 envoy


This not a fuse problem. When you switch to A4WD or 4HI, do the indicator light for those positions stay on solid or do they blink and then return to 2HI position? If so, then there is probably a problem with the transfer case actuator/motor.

Aug 10, 2012 | 2005 GMC Envoy

2 Answers

My 2002 chevy silverado 4x4 will not disengage from 4 wheel lo to 4x4 hi, 2 wheel drive or 4x4 auto. I tried while driving forward , backwards and sitting. The 4x4 activates by push button. Any...


The issue is usually loaded gears. The secret is to try circles, one way and then the other. This preload is why 4x4 is supposed to be used on loose surfaces....The gears will disengauge after they unload.

Feb 23, 2011 | 2002 Chevrolet Silverado 1500

2 Answers

4wd does not work


Electronic Shift On the Fly (ESOF) Operation
The ESOF system is an electronic shift 4x4 system that allows the operator to choose between two different 4x4 modes as well as 2-wheel drive. The operator can switch between 2WD and 4WD HIGH mode at speed. To engage or disengage LOW Range, the vehicle speed must be less than 5 kph, the brake depressed, and the transmission must be in NEUTRAL.

The transfer case is equipped with an electromagnetic clutch which is located inside the case. This clutch is used to spin up the front drive-line when shifting from 2WD to 4x4 High mode at speed. When the control switch on the instrument panel is turned, the generic electronic module (GEM) recognizes that a shift has been requested and activates the electromagnetic clutch and the relays which power the transfer case shift motor. When the shift motor reaches the desired position as determined by the contact plate position inputs to the GEM, power to the shift relays and motors will be removed. When the transfer case front and rear output shafts are synchronized, the spring loaded lockup collar mechanically engages the main-shaft hub to the drive sprocket. Finally, the front axle collar is engaged and the electromagnetic clutch is deactivated.

Shift Between 2WD and 4x4 HIGH:
Shifts between 2WD and 4x4 HIGH can be made at speed. Listed below are the inputs and outputs needed by the GEM to execute a change between any of these modes.

Feature Inputs:
*4WD Mode Switch (Various resistances).
*Contact Plate Position Inputs A, B, C, D (grounded when closed, open circuit when open).

Feature Outputs:
*4x4 Shift Motor Relay Outputs
*Transfer Case Clutch Relay (grounded when relay is on, open circuit when relay is off).
*4x2/4x4 Vacuum Solenoid (grounded when activated, open circuit when deactivated).
*Cluster Indicators (ground when activated, open circuit when deactivated).

Shifting Into/Out of 4WD LOW:
When shifting into or out of 4WD LOW, the GEM requires that the vehicle speed be less than 5 kph, the brake is applied, and the transmission is in NEUTRAL.

Feature Inputs:
*4WD Mode Switch (Various resistances).
*Contact Plate Position Inputs A, B, C, D (grounded when closed, open circuit when open).
*VSS Sensor (Sinusoid Signal: 0.7V-20V, 2.2 Hz/mph).
Brake Input (battery voltage when brake is depress, open circuit when not activated).
*Transmission Range Sensor (grounded when transmission is in NEUTRAL, open circuit otherwise).
8Start/Clutch Depressed Input

Feature Outputs:
*4x4 Shift Motor Relay Outputs
*4x2/4x4 Vacuum Solenoid (grounded when activated, open circuit when deactivated).
*Cluster Indicators (grounded when activated, open circuit when deactivated).

4WD Mode Switch
A rotary switch allows the vehicle operator to choose between 2WD, 4WD HIGH, and 4WD LOW modes of 4x4 operation.

GEM Module
The Generic Electronic Module (GEM) controls the operation of the 4x4 system

Vehicle Speed Sensor
The vehicle speed sensor (VSS), mounted in the rear of the transfer case, informs the GEM of the vehicle speed.

Transfer Case Shift Motor Sense Plates

The shift motor sense plate, an integral part of the electric shift motor, informs the GEM to the positions of the transfer case

Transmission Range Sensor
Located on the left side of the transmission, this sensor informs the GEM when the transmission is in the NEUTRAL position.

Electric Shift Motor
The electric shift motor, mounted externally at the rear of the transfer case, drives a rotary cam which moves the mode fork and range fork within the transfer case to select between the 2WD, 4WD HIGH, and 4WD LOW positions.

4x4/4x2 Vacuum Solenoids
These two solenoids are attached to the upper RH side of the engine compartment dash, and alternately route vacuum to the vacuum motor which engages/disengages the center axle disconnect collar in the front axle assembly.

4x4 Shift Motor Relay
A module containing two relays which under the control of the GEM, shift the transfer case shift motor between the 2WD, 4WD HIGH, and 4WD LOW modes.

Transfer Case Clutch Relay
An electromechanical relay is used to activate the transfer case clutch within the transfer case.

Good luck and hope this helps,but start with the simple and check the fuses and wire harness. Both white/light blue stripe wires should have 12V in run. The GEM will ground the left side (closest to engine) solenoid to disengage the front axle. It will ground the the right side solenoid (closest to fender) to engage the front axle. If the GEM doesn't see Neutral it will not let the truck come out of 4Lo. If the GEM had water leaking on it it may well be the root of the problem. The shift motor only has power when the GEM sends it a signal to move the shift lever. Once the shift is completed the motor shuts off. There are 2 wires that control the shift motor. A yellow and an orange. The GEM alternates between 12v and Ground to these wires to control which way the motor turns. The GEM uses the transfer case shift relay module to control the power to the motor. There are contact plates inside the shift motor assembly that indicate the position that the shift lever is in. This is what the GEM used to know what the T-case is doing. Any one of these components can fail.







Jan 10, 2010 | 2002 Ford Explorer

1 Answer

96 s10 blazer 4x4 wont work lights flash on dash but shift transfree case put new motor on transfree case


Listen for the TCCM (transfer case control module) to "click" when 4X4 is activated behind passenger kicker panel just in front of passenger door near floorboard. If it clicks then is activating and with the new motor on transfer case that would make me think it has something to do with the 4X4 vacuum lines. If you look under the battery tray you will find the vacuum canister that activates the front hub when 4X4 is activated. take out ur battery and position it so you can still have it hooked up or with jumper cables and still see the canister and turn your truck on and engage 4X4 to see if vacuum canister activates to lock in front hub, if not just follow and check vacuum lines. Also check, ALL, fuses as there are many fuses that in my opinion are miss marked as with the logic side of TCCM is ran through the fuse marked for the Dome Light. Have also heard of parking lamps having something to do with it too... just a few suggestions from things I had to go through with mine

Dec 15, 2009 | 1994 Chevrolet S-10 Blazer

1 Answer

Transfer case stays in 4wd


If it is auto 4wd it could be a speed sensor problem. There are 2 sensors on the drive train. When there is a difference of speed between them it activates the auto4wd. If one is malfunctioning it thinks there is a speed difference and locks up the transfer case. Driving it this way on dry ground will break the tranfer case. Have the codes cheked out to see if there is a problem with the sensors.

Oct 28, 2009 | Ford Explorer Cars & Trucks

1 Answer

Why does a 1999 Suburban Auto Transfer case not engage and not go into 4X4 or auto 4X4 and push button lights on dash do not light when the fuse is good?


The 4x4 switch on the dash likes to take a dump in those years. They also like to eat encoder motors. If you have a way of checking it, try and get the codes out of the transfer case modual. b2725 means you need a new 4x4 switch on the dash. c0327 means you need a new encoder motor. There are a bunch of other codes that can be in there. But I'll take a guess and say those will be the ones you'll see.

Oh and for what it's worth the encoder motor is the the thing on the transfer case that shifts it. It's a electric motor. And it's NOT cheap! So make sure you find out if it's really bad before you put one in.

Oct 16, 2009 | 1999 Chevrolet Silverado 1500

1 Answer

Stuck in 4x4 high


Could be the switch or the controller motor on the transfer case.

Apr 19, 2009 | 2008 Ford F-150

1 Answer

4x4 on a 2001 s10


when the transfer case shifts into 4wd it activates a vaccum switch on the transfer case which sends vaccum to the accuator for the front axle. the accuator pulls a cable that locks in the axle. the switch on the transfer case is a well known problem. check for vaccum in and out of this switch in 4wd. if you have vaccum out then check the accuator under the battery. If the vaccum switch on the transfer case is bad you can find one at most parts store in the HELP section #49315. please rate if this helps

Nov 22, 2008 | 2001 Chevrolet S-10

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