Service 4wd help

[Hardbody255]

05 Tahoe I have a service 4wd message pop up. I've ran the codes and changed the switch all lights light up like they should and the 4wd shifts like it should but I'm still getting the service 4wd message. Anybody else had this problem?

 

[Doubeleive]

If it's not the switch on the dash then might be the encoder motor or the solenoid on the front differential, shorted/broken wire/bad connection.
have you had any work down to it lately? I had the same problem once everything worked fine, but turned out something was unplugged either on the transfer case or transmission

 

[Hardbody255]

No work done on it except I replaced the encoder motor ring but that didn't fix it either. The message won't pop up if it's just sitting still but when you drive it that's when the message pops up.

 

[wjburken]

I’m assuming you have checked the fluid level in your transfer case.

 

[Fless]

It would be good to look into it with a Tech 2, or with a code reader that can look at the 4x4 system. Could be something common, or maybe something not so common like one of the speed sensors on the tranny and transfer case. Really, we're just guessing here.

When you ran the codes, what specific codes did you get? Are they all still there? If the "service" message is there you should have a code or two.

 

[George B]

It would be good to look into it with a Tech 2, or with a code reader that can look at the 4x4 system. Could be something common, or maybe something not so common like one of the speed sensors on the tranny and transfer case. Really, we're just guessing here.

When you ran the codes, what specific codes did you get? Are they all still there? If the "service" message is there you should have a code or two.

2x

could be a component or a ground issue.
Check the ground on the frame under the drivers floor.

 

[PNWYukon]

The 4WD transfer case encoder motor position sensor or the selector switch may fail causing the service 4WD message to be displayed. Fault code(s) stored in the transfer case control module will be of assistance in determining the exact fault causing the message to be displayed.

 

[Hardbody255]

Fluid level is good and these codes were in it before I changed the encoder ring.

 

[Fless]

Wonder what codes it has now after the encoder ring was changed?

Some of the resources I viewed indicate that the transfer case control module should be reprogrammed. That first code, though, I think might point to one of the two or three speed sensors, which may be cured by reprogramming the TCCM.

 

[PNWYukon]

DTC C0306
Circuit Description
The transfer case motor is a bi-directional, permanent magnet, DC motor. When energized, through motor control A or motor control B, the ground is provided by the opposing motor control circuit and then grounded through the transfer case shift control module ground circuit, the motor, through a series of gears, rotates a shaft which moves the mode and range forks to shift the transfer case between the following modes:

• 4LO
• AWD
• Neutral

This DTC detects an open, short to voltage or short to ground in the motor control A or motor control B circuits, or an open, or short to ground inside the motor.

DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC C0306 Motor A or B Circuit Malfunction

Conditions for Running the DTC

• The ignition is ON.
• The system voltage is 9 - 18 volts.

Conditions for Setting the DTC

• The system tests the motor circuits by testing for unwanted voltage.
• Then, the system supplies voltage on each of the motor circuits and reads the voltage back on the other circuit.
• If the system detects a condition with the circuits, the DTC is logged. The transfer case shift control module senses a low voltage return in the motor control A or motor control B circuits when a high voltage is expected.
• The fault must remain current for 1.2 seconds to set the DTC.

Action Taken When the DTC Sets

• All shifting is disabled.
• The SERVICE 4WD indicator will remain illuminated for the remainder of the current ignition cycle.

DTC C0321
Circuit Description
The transfer case shift control module controls the transfer case lock solenoid.

The transfer case lock solenoid is released by being energized. This is accomplished by grounding the lock solenoid control circuit during gears shifts, and in the AUTO 4WD mode. Locking action is applied when power or ground are taken away from the lock solenoid, the transfer case motor is prevented from moving. The system is capable of providing a 2HI, 4HI and 4LO lock-up without the need of additional vehicle power to hold the transfer case in these positions.

This DTC detects an open lock solenoid coil, open motor lock control circuit, or an open motor lock feed circuit.

DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC C0321 Transfer Case Lock Circuit Malfunction

Conditions for Running the DTC

• The ignition is ON.
• The system voltage is 9 - 18 volts .

Conditions for Setting the DTC

• The transfer case shift control module tries to unapply, turn OFF the lock solenoid by grounding the motor control circuit.
• If the module does not sense the battery voltage at the motor lock control circuit prior to applying the motor lock, the DTC sets.
• Transfer Case Lock output reads back as a high voltage when a low voltage is expected.

DTC C0327
Circuit Description

The transfer case shift control module consists of four encoder channels, which are supplied 5 volts. These four channels are P, C, A, and B, each running to a switch located inside the encoder/motor assembly. When a particular encoder channel is active, the switch is closed and 5 volts flow through the encoder signal return circuit. If the module wants to request motor position, a low side driver pulls the voltage low on the encoder signal return and the corresponding channel circuit, indicating motor position.

The transfer case shift control module supplies 5 volts on all the channels. As these channels are pulled to ground, the module can interpret the location of the transfer case shift position.

This DTC detects an open, high resistance or a short to voltage in the encoder signal return circuit, or an open, high resistance or short to voltage in the encoder channel circuits.

DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC C0327 Encoder Circuit Malfunction

Conditions for Running the DTC

• The ignition is ON.
• The system voltage is 9 - 18 volts .

Conditions for Setting the DTC
The transfer case shift control module reads back a high voltage when a low voltage is expected, or low voltage when a high voltage is expected on the encoder channel circuits, or the encoder signal return circuit.

Action Taken When the DTC Sets

• All motor activity stops.
• All the transfer case shift control switch mode indicators are commanded OFF.
• The SERVICE 4WD indicator is latched on for the remainder of the current ignition cycle.
• If a new mode is requested while the DTC is present, either current or history, the indicator for the mode requested flashes for 15 seconds and then goes out.