Service 4X4 light goes on after a short drive

Hi,

I don't feel the hubs would cause the transfer case issue. I suspect it deals with the encoder motor. If you look at pic 1, I attached an exploded view of the transfer case and circled the encoder motor. The first thing I suggest is to inspect the plug for pushed in pins, corrosion, or any evidence of damage. That it checks good, here are directions for testing the encoder motor. Pic 2 correlates with the directions.

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1999 Chevy Truck K 2500 Suburban 4WD V8-454 7.4L VIN J SFI
Transfer Case Will Not Complete A Mode or Range Shift
Vehicle Transmission and Drivetrain Transfer Case Testing and Inspection Symptom Related Diagnostic Procedures NVG 243-NP1 (Two Speed Selectable) Diagnosis By Symptom Transfer Case Will Not Complete A Mode or Range Shift
TRANSFER CASE WILL NOT COMPLETE A MODE OR RANGE SHIFT
Transfer Case Will Not Complete A Mode or Range Shift

Circuit Description

This symptom indicates that the transfer case encoder motor circuits are not functioning properly. This symptom is similar to DTC 003 but differs because the counter inside the transfer case control module (TCCM) has not yet set DTC 003. One of the following conditions may exist.

- One of the internal power relays in the (TCCM) is not energizing or deenergizing.
- An open exists in the Battery Positive Voltage, Ground, Motor Control A or Motor Control B circuits.
- A short to ground exists in the Battery Positive Voltage, Motor Control A or Motor Control B circuits.
- A short exists within the motor or TCCM.

The transfer case encoder motor has a bi-directional permanent magnet, D.C. Motor. When a shift request is made by the TCCM voltage will be applied through one of the motor control circuits and the TCCM will provide the ground through the other motor control circuit. When a shift is requested in the opposite direction, the TCCM will reverse polarity on these two circuits. The motor through a series of gears, rotates a shaft which moves the mode and range forks to shift the transfer case between gears.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

2. This step tests the functionality of the transfer case shift control system.

Transfer Case Will Not Complete a Mode or Range Shift

pic 2

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Let me know what you find or if you have other questions.

Take care,
Joe

Hi,

Just for curiosity, is the brake light stay on or the ABS light?

Joe

Hi,

Let me know what you find or if you have other questions.

Take care,
Joe

Hi,

Is it the wiring to the wheel speed sensor?

Let me know.
Joe

Hi,

It's an ABS sensor. The one in the pic shows the entire hub assembly with the sensor. You could just replace the sensor.

Here are the directions. The attached pics correlate with the directions.

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1999 Chevy Truck K 2500 Suburban 4WD V8-454 7.4L VIN J SFI
Wheel Speed Sensor Replacement
Vehicle Sensors and Switches Sensors and Switches - Brakes and Traction Control Wheel Speed Sensor Service and Repair Procedures Wheel Speed Sensor Replacement
WHEEL SPEED SENSOR REPLACEMENT
REMOVAL PROCEDURE

pic 1

1. Raise vehicle.
2. Remove tire and wheel.
3. Remove brake caliper.
4. Remove the hub and rotor.
5. Remove wheel speed sensor mounting clip (2) on the control arm.

Pic 2

6. Remove wheel speed sensor mounting clip (2) on the frame rail.

Pic 3

7. Remove wheel speed sensor electrical connector (6).

NOTICE: Carefully remove the sensor by pulling it straight out of the bore. DO NOT use a screwdriver, or other device to pry the sensor out of the bore. Prying will cause the sensor body to break off in the bore.

IMPORTANT: The wheel speed sensor mounts into a bore that leads to the center of the sealed bearing. Use caution when cleaning or working around the bore. Do not contaminate the lubricant inside the sealed bearing. Failure to do so can lead to premature bearing failure.

8. Remove wheel speed sensor from hub and bearing assembly.

INSTALLATION PROCEDURE

pic 4

IMPORTANT: The new speed sensor will have a new O-ring. Dispose of the old O-ring. Lubricate the new O-ring lightly with bearing grease prior to installation. You may also lubricate the sensor just above and below the new O-ring. Do Not lubricate the bore.

1. Install sensor into the hub and bearing assembly (5).
Tighten the sensor mounting bolts to 18 Nm (13 ft. Lbs.).

IMPORTANT: The new sensor has new mounting clips already installed on the wire. Do not reuse the old clips.

Pic 5

2. Install wheel speed sensor electrical connector (6).

Pic 6

3. Install wheel speed sensor mounting clip (2) to the frame rail.

Pic 7

4. Install the wheel speed sensor mounting clip (2) to the control arm.
5. Install the hub and rotor.
6. Install brake caliper.
7. Install tire and wheel.

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I hope this helps.

Take care,
Joe

Hi Tom.

No problem. Take your time. When you have the chance, let me know. I'm not too far behind you and know exactly what you mean. LOL

Take care,
Joe