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AutoTech08
AutoTech08, Workshop owner
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Experience:  Diploma in Automotive Engineering, 30 years working experience.
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How do I unlock the 4wd in my 99 toyota 4runner limited

Resolved Question:

I need to drive a lot in highway but can't unlock the 4wd I know I can't go over 30mph while on 4wd, can u please tell me, How do I unlock the 4wd in my '99 toyota 4runner limited? manual is in french, it has H2.H4, H4L, N, L4L and the 4wd button on the side, prompt answer will be appreciated
Submitted: 8 years ago.
Category: Toyota
Expert:  AutoTech08 replied 8 years ago.

Hi there,

 

Hope the following are what you are looking for.

 

INTRODUCTION

NOTE: To engage Automatic Disconnecting Differential (ADD) actuator, vehicle speed must be 62 mph (100 km/h) or less. Also, do not attempt to shift into or out of 4WD while wheels are slipping. Always stop wheel spin first to avoid damaging 4WD components.

 

4WD operation can be controlled by transfer case shift lever and 2-4 selector switch mounted on shifter. With transfer shifter in "H2-H4" position, selector switch can be used to lock ADD actuator. This can be used on all types of road surfaces, and will increase traction over conventional 2WD setting.

NOTE: "L4 L " (low range 4WD - locked) and "H4 L " (high range 4WD - locked) settings are not to be used on dry paved surfaces, as drive system and locking mechanism can be damaged as a result. Before shifting to "H4 L ", reduce vehicle speed to 62 mph (100 km/h) or less. Before shifting to "L4 L ", bring vehicle to a complete stop and place transmission in neutral.

 

"H4 L " setting is used for increased traction when wheel slipping still occurs in "H2-H4" position. This setting will lock both the center differential and ADD actuator for front wheels, regardless of 2-4 selector switch position.

"L4 L " setting offers maximum power and traction for hard pulling in situations that vehicle cannot negotiate even in "H4 L " mode.

 

AUTOMATIC DISCONNECTING DIFFERENTIAL ACTUATOR

Automatic Disconnecting Differential (ADD) allows engagement of front differential from 2WD to 4WD while vehicle is moving. On vehicles with ADD, a flange is mounted on front hub which is splined onto axle shaft connected to side gear shaft on front differential. Locking hubs are not used with ADD.

When transfer case is shifted into or out of 4WD, ADD is controlled by operation of 2 ADD solenoids that direct vacuum to appropriate actuator diaphragm. ADD actuator engages clutch sleeve with intermediate shaft in front differential and side gear shaft, providing 4WD operation. When vehicle is in 4WD, an indicator light on instrument panel will be illuminated.

 

PARK/NEUTRAL POSITION SWITCH

Park/Neutral Position (PNP) switch delivers an input signal to ECM indicating transmission gearshift lever position. Switch is located on side of transmission.

 

2-4 SELECT SWITCH

2-4 select switch sends a request signal to 4WD ECU, which activates corresponding actuator vacuum switching valve. Switch is located on transfer case shift lever knob.

 

TRANSFER SHIFT ACTUATOR ASSEMBLY

Transfer shift actuator assembly shifts transfer case from one configuration to another from signals sent by 4WD ECU.

 

VEHICLE SPEED SENSOR

Vehicle speed sensor (VSS) signal is generated by sensor mounted in transmission extension housing. Additionally, on ABS-equipped vehicles, ABS wheel speed sensors send signals to ABS ECU, which then converts them to a 4-pulse signal. On all models, signals are then delivered to instrument cluster, where they are converted into a more precise rectangular waveform. VSS signal is then sent to various control modules, including 4WD ECU. Signal is used to prevent shifting into 4WD above 62 miles per hour.

 

L4 POSITION SWITCH

The L4 position switch sends a signal to 4WD ECU when transfer case gear position is L4 L .

 

4WD ELECTRONIC CONTROL UNIT

4WD electronic control unit monitors all inputs from position switches, VSS, PNP switch, and select switches to control transfer shift actuator and ADD actuator, which controls all transfer case shifts and gear selections.

 

4WD POSITION SWITCH

Two 4WD position switches send signals to 4WD ECU to indicate transfer case gear position.

 

 

 

 

Customer: replied 8 years ago.

It's not working, it has the picture in the dash board with the 4 tires in green and the middle with orange and all 5 lights are flashing at the same time, no matter what I put in on they don't stop flashing it seems to be locked completely when I'm going to turn the tires are really stiff. What should I do?

Expert:  AutoTech08 replied 8 years ago.

Hi there,

 

The system is malfunctioning and there are a variety of possible reasons.

 

1. 4WD ECU.

2. Control solenoids

3. Vacumns.

 

graphic

 

I would sugggest preliminary checks and doing a component test.

1. Unplug 4WD ECU and check connectors for contaminations.

2. Check wiring routing and connections.

 

.

COMPONENT TESTS

1. AUTOMATIC DISCONNECTING DIFFERENTIAL ACTUATOR (CLUTCH HUB & SLEEVE)

2. AUTOMATIC DISCONNECTING DIFFERENTIAL ACTUATOR (VACUUM DIAPHRAGM)

3. AUTOMATIC DISCONNECTING DIFFERENTIAL RELAY

4. AUTOMATIC DISCONNECTING DIFFERENTIAL SOLENOIDS

5. AUTOMATIC DISCONNECTING DIFFERENTIAL SWITCH

6. TRANSFER SHIFT ACTUATOR MOTOR OPERATION.

7. TRANSFER SHIFT ACTUATOR MOTOR OPERATION

8. 2-4 SELECTOR SWITCH.

 

 

 

 

Customer: replied 8 years ago.
Tried all that and it hasn't changed, what else can I do?
Expert:  AutoTech08 replied 8 years ago.

Hi there,

 

If you have all the component test and none of them are faulty, the next option is to try substituting the 4WD ECU. It could be faulty and locking itself up. Before doing that, try checking the ground for the 4 WD ECU, terminal # XXXXX ( Blacl/White wire ). If you have an ohmmeter, the resistance between it to body ground should be as close to ) as possible, anything more than 1 ohm might mean a bad ground.

 

See if the following test yields any results.

 

graphic

 

graphic

 

graphic

 

 

 

AutoTech08 and 5 other Toyota Specialists are ready to help you
Customer: replied 8 years ago.

Hello again, another question, the $15 dollar has already posted in my account do I need to accept the answer or would I get charged another $15 dollars?

As for the car, I think I have to changer the switch in the motor of the 4x4 everything else seems fine so I'll give that a try.

 

Thank You

Expert:  AutoTech08 replied 8 years ago.

Hi there,

 

If you did not click Accept, the money is still in your account and will not be paid out.No extra amount would be charged unless you click ACCEPT repeatedly.

 

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