Question about GMC Sierra

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I have an 05 GMC Sierra and for the last few years ive had 4wd issues it all started when i was driving out at a farm and hit a hard bump the service 4wd light came on for a minut then went back off a

Changed: actuator switch encoder switch fuses checked grounds codes: B0790-Transfer case neutral indicator circuit malfunction B2725-Mode switch circuit malfunction C0306-Motor A/B circuit malfunction C0321-Transfer case lock circuit malfunction C0327-Encoder circuit malfunction

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  • GMC Master
  • 15,575 Answers

DTC B0790 Transfer Case Neutral Indicator Circuit Malfunction
The Neutral indicator circuit consists of an ignition 3 voltage circuit and a Neutral indicator control circuit. When the Neutral mode has been selected by the driver, current is supplied to the Neutral indicator by the ignition 3 voltage circuit, traveling through the Neutral indicator LED at which time the transfer case shift control module supplies the ground through the Neutral indicator control circuit. This DTC detects an open, short to ground, or a short to voltage.
2
Install a scan tool.
Turn the ignition ON, with the engine OFF.
With the scan tool, command the Neutral Indicator Light ON and OFF.
Does the Neutral Indicator Light turn ON and OFF with each command?
YES - Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
NO - Go to Step 3
Turn the ignition OFF.
Remove the transfer case select switch.
Disconnect the connector on the transfer case select switch.
Turn the ignition ON.
Probe the ignition 3 voltage circuit with a DMM that is connected to a good ground.
Does the DMM indicate battery voltage?
YES - Go to Step 4
NO - Go to Step 10

5
Does the DMM continue to indicate battery voltage with each command?
YES - Go to Step 7
NO - Go to Step 6
6
Test the neutral indicator control circuit for a short to voltage or an open. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
YES - Go to Step 13
NO - Go to Step 9
7
Test the control circuit of the neutral indicator for a short to ground. Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 13
Go to Step 9
8
Inspect for poor connections at the transfer case shift control switch. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 13
Go to Step 11
9
Inspect for poor connections at the harness connector of the transfer case shift control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 13
Go to Step 12
10
Repair the ignition 3 voltage circuit of the transfer case select switch for an open, a high resistance, or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you complete the repair?
Go to Step 13
--
11
Replace the transfer case select switch. Refer to Transfer Case Shift Control Switch Replacement .
Did you complete the repair?
Go to Step 13
--
12
Replace the transfer case shift control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.
Did you complete the repair?
Go to Step 13
--
13
Use the scan tool in order to clear the DTCs.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC set?
Go to Step 2
System OK

Posted on Mar 03, 2018

  • Jeff Armer Mar 03, 2018

    DTC B2725 ATC Mode Switch Circuit Malfunction
    Circuit Description
    The range/mode switch circuit consists of 5 modes. The transfer case shift control module supplies 5 volts to the switch through the 5-volt reference circuit. The current travel through the resistor of the currently active mode. The current is then returned to the transfer case shift control module through the switch signal circuit.

    The transfer case shift control module constantly monitors this signal voltage to determine the condition of the mode switch circuit.

    When each of the modes are selected they complete a circuit through their own specific resistor. The transfer case shift control module continuously monitors the switch input to determine whether the Neutral, AWD, 2HI, 4HI, or 4LO mode was selected by the driver.

  • Jeff Armer Mar 03, 2018

    DTC C0306 Motor A or B Circuit Malfunction
    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 ranges:

    • 2HI

    • 4HI

    • 4LO

    • AUTO 4WD

    • 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 C0321 Transfer Case Lock Circuit Malfunction
    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 C0327 Encoder Circuit Malfunction
    Circuit Description
    The transfer case encoder is an analog sensor that returns a signal that represents the physical position of the transfer case sector shaft. This signal represents the mode or position that the transfer case is currently in. This sensor is made up of the following 3 circuits:

    • 5-volt reference circuit

    • Encoder signal circuit

    • Encoder low reference circuit

    This DTC detects an out of range reading from the encoder signal, a short to voltage on the 5-volt reference circuit.
    Conditions for Setting the DTC
    The transfer case shift control module has a predefined range, 0.5-4.5 volts, in which the encoder feed back should stay within. The DTC sets if the encoder signal feed back falls out of this range.

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6 Suggested Answers

6ya6ya

6ya staff

  • 2 Answers

SOURCE:

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Posted on Jan 02, 2017

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BB1BUD

  • 462 Answers

SOURCE: 4wd issues!!! When I start the truck, all 3

THE 4WD SWITCH IS A PROBLEM. ALSO THE GROUND CONNECTOR ON THE FRAME CLOSE TO THE DRIVERS DOOR IS A PROBLEM. IT USUALLY HAS A COATING OF THE UNDERCOAT MATERIAL ON THE FRAME THAT IS NOT REMOVED BEFORE THE CONNECTORS ARE PUT IN PLACE.

THERE ARE 2 BOLTS THERE THE OTHER IS AN ABS GROUND CLEAN OFF THE UNDERCOATING FIRST, PUT DIELECTRIC GREASE ON THE CONNECTION POINTS, THEN COVER THEM IN SPRAY ON UNDERCOATING. THIS IS A CHEAP FIX TRY IT FIRST.

RATE ME PLEASE.

Posted on Jul 24, 2009

Anonymous

  • 32 Answers

SOURCE: 4wd light flashes and have replaced the front

after looking at the schematics for this vehicle, I can say with great certainty that you might have something wrong in your front axle on a straight axle model that wont let the servo engage the front axle. Now if you have independant front suspension, then where the servo motor goes into the transfer case could be the problem. pull the servo motor from the case/axle and look at the engaging mechanism. You are looking for worn parts that could cause binding or broken parts. This servo motor gets its command voltage from the ecm. The signal for the ecm generates from the transmission and your in cab switch. If you can hear the motor trying to engage, then all the other factors are working up to the motor arm. The light is just a by product of the ecm trying to engage the front axle

Posted on Sep 24, 2009

Anonymous

  • 1 Answer

SOURCE: Just replaced my encoder motor, front actuator,

you may have to replace your trasfer case control module its right under dash driver side easy to access mine just went out it was throwing c0359 code 4 low cirut and service four wheel drive would come on dash although the 4wd works great it just throws the code.

Posted on Jan 27, 2010

roniecon

Ronny Bennett Sr.

  • 6927 Answers

SOURCE: hey, i have 2002 chev 1/2 ton, 4wd wont disengage.

Most likely the problem.

Posted on Jan 28, 2010

Testimonial: "thank you, will keep you posted"

Anonymous

  • 1 Answer

SOURCE: Service 4wd

my 4WD shifts on it's own, and back out when i turn the engine on and off. I thinks it's a sensor but not sure.

Posted on Feb 23, 2010

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