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GMKindl
GMKindl, ASE Certified Technician
Category: Chevy
Satisfied Customers: 389
Experience:  15 Years Master ASE Certified, ASE Advanced Engine Performance, GM Platinum Pro Service Guild
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I have a 2005 Chevy Suburban and the Service 4wd lite is on

Customer Question

I have a 2005 Chevy Suburban and the Service 4wd lite is on and all tne lights are out on the auto 4wd, 2wd, 4wd, 4wd low range are out. The problem started by going into 4wd by itself.

Thanks
Mike
Submitted: 4 years ago.
Category: Chevy
Expert:  GMKindl replied 4 years ago.
Hello and welcome to Just Answer. Does 4wd work when you push the buttons?
Customer: replied 4 years ago.
No, none of the buttons cause anything to happen. When I first turn the car switch on all the indicator lights come on and then immediately go out which tells me the indicator lights are working.
Expert:  GMKindl replied 4 years ago.
Ok. This seems to be a somewhat common failure on some of the GM 4wd trucks. Typically the problem is that the Transfer Case Encoder Motor Position Sensor (Encoder motor is the motor that shifts the transfer case) is giving false position signals and causing the phantom 4wd shifting and also the Service 4wd message. The sensor itself is located inside the encoder motor and can be serviced separately from the encoder motor. If you were to take the vehicle to a shop and have diagnosis performed it would likely yield a C0327 code set in the Transfer Case Control Module (TCCM). There may also be a few other codes. GM actually has a service bulletin that outlines this repair as well as advises checking a few other things. I would say that 99% of the time the sensor fixes this problem. I will post the portion of the bulletin that applies to your truck.

Subject:DTC C0327 with or without Additional DTCs Setting
Models:2004-2006 Buick Rainier
2003-2006 Chevrolet Avalanche, Silverado Classic
2003-2006 Chevrolet Suburban, Tahoe
2002-2008 Chevrolet Trailblazer
2002-2008 GMC Envoy
2003-2006 GMC Sierra Classic, Yukon, Yukon XL
2002-2004 Oldsmobile Bravada
with Four Wheel Drive (4WD) Only


This PI is being superseded to update model years and connector numbers. Please discard PIP3061E.


The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:

In "K" trucks with 246 and 263 transfer cases:

DTC C0327 stored in the TCCM only or C0327 in TCCM along with P0836 in TCM and P0500 in PCM.

In "T" trucks 126 and 226 transfer cases:

DTC C0327 with or without additional DTCs setting.

Recommendation/Instructions:

For "K" trucks with 246 and 263 transfer cases:

This information supplements TSB 03-04-21-001D to include additional diagnosis.

  1. Refer to published service procedures for diagnosing DTC C0327 which includes basic diagnostics i.e.:
  2. Visually check the TCCM wiring harness for pinched/chaffed concerns.
    Additional Info: In particular check the TCCM harness chaffing at the brake cable release spring.
    Check the pin/terminal fit at the encoder motor, TCCM and under hood relay center. Pay particular attention to Connector C1, pin A7 at the TCCM.
    Check the TCCM, body, chassis and engine ground credibility. Remove and clean any material that may cause high resistance in the circuit i.e. paint, undercoating, etc. Ensure these grounds are secure and perform a voltage drop test and record the readings for these grounds. If the engine, chassis and body grounds are poor the encoder motor or the TCCM can be used as an alternative ground path.
    If DTC C0327 can be duplicated in any position, check the scan tool data for the Encoder Signal Voltage going high or low. If the Encoder Signal Voltage is going high, check the Encoder Low Reference circuit for an open or high resistance. If the encoder Signal Voltage is going low, check the 5 Volt Reference and Encoder Signal circuits for an open or high resistance. Check the C151 connector on the left fenderwell for possible poor connection.
    If DTC C0327 sets when making a shift into 4 HIGH only or during a slip event in auto 4WD, inspect the Transfer Case fluid for contamination. If fluid is contaminated remove the Transfer Case and inspect for mechanical concerns.
  3. Additional Information: Ground Locations
  4. TCCM Ground: G110.
    TCCM Ground for the Mode Switch: G203.
    Note: If there are no other component issues that share the same ground (example: OnStar shares G203) then it may not be necessary to check G203.
    If no concerns have been found with the above checks, replace the encoder sensor.
Customer: replied 4 years ago.

What is the procedure for replacing the encoder sensor and does the transfer case control module need reprogramming after the encoder sensor is replaced.

 

Thanks

Mike

Expert:  GMKindl replied 4 years ago.
The procedure is posted below for your reference. There is an updated calibration for your year and model that also address a C0327 code. If you do find that code present then I would advise having the TCCM reprogrammed as well.

Removal Procedure

Important: For ease of reassembly, shift the transfer case to Neutral prior to removing any components.


    Object Number:(NNN) NNN-NNNN Size: SH

  1. Remove the encoder motor. Refer to Transfer Case Encoder Motor Replacement .
  2. Place the encoder motor on a clean work bench.
  3. Remove and discard 2 screws (2) from the motor cover.
  4. Remove and discard 2 screws (1) from the casting.
  5. Remove the cover.
  6. Remove and save the shim on the output gear.
  7. Remove and discard the orange rubber seal from the cover.

  8. Object Number:(NNN) NNN-NNNN Size: SH

  9. Remove the output gear (1).

  10. Object Number:(NNN) NNN-NNNN Size: SH

  11. Disassemble the harness connector (1) from the encoder.
  12. Remove the encoder from the output shaft using a flat-tipped screwdriver.

Installation Procedure


    Object Number:(NNN) NNN-NNNN Size: SH

  1. Assemble the harness to the NEW encoder with the connector legend "TOP" (1) and the encoder part number facing up.
  2. Assemble the output shaft into the encoder being sure to align the encoder tab with the groove on the shaft.
  3. Ensure the encoder is seating properly on the output gear.
  4. Place the output shaft/encoder on the casting.
  5. Place the grommet harness on the casting slot, the flat area on the grommet will be facing up.

  6. Object Number:(NNN) NNN-NNNN Size: SH

  7. With the output gear/encoder assembly in hand, carefully align the casting and output gear timing marks (1).

  8. Object Number:(NNN) NNN-NNNN Size: SH

  9. At the same time be sure to align the encoder phasing post (1) with the phasing slot (2) in the casting and insert the shaft into the bushing.
  10. Verify that the output gear and idler gear are engaged properly.
  11. Seat the harness wires on the casting channel.
  12. Place the shim on the output shaft gear.
  13. Press a NEW seal into the cover.
  14. Notice: Refer to Fastener Notice in the Preface section.


    Object Number:(NNN) NNN-NNNN Size: SH

  15. Install the cover.
  16. Install 2 NEW screws (1) to the casting.
  17. Tighten
    Tighten the screws to 2 N·m (18 lb in).

  18. Install 2 NEW longer screws (2) to the motor cover.
  19. Tighten
    Tighten the screws to 3 N·m (26 lb in).

  20. Install the encoder motor. Refer to Transfer Case Encoder Motor Replacement .
GMKindl, ASE Certified Technician
Category: Chevy
Satisfied Customers: 389
Experience: 15 Years Master ASE Certified, ASE Advanced Engine Performance, GM Platinum Pro Service Guild
GMKindl and 7 other Chevy Specialists are ready to help you
Customer: replied 4 years ago.

What is the procedure for Transfer Case Motor Replacement. I tried to open Transfer Case Encoder Motor Replacement but it said I was Not authorized. Also, how do you reprogram the TCCD if I need that done.

 

Thanks

Mike

Expert:  GMKindl replied 4 years ago.
The TCCM will need to be reprogrammed by either a dealer or an independent service repair shop that is capable of programming. I woould suggest calling around to a few shops in your area to see if they can do it and how much it will cost. You will need to take the whole truck to them to have it programmed. It can be done before or after you replace the Encoder sensor. If you have it done after then all codes will be cleared from that module during programming, not a big deal but at least it will be code free then.

As for the Encoder Motor replcement here you go:

Removal Procedure


    Object Number: 829147  Size: SH

  1. Remove the transfer case shield, if equipped. Refer to Transfer Case Shield Replacement .
  2. Remove the front propeller shaft. Refer to Front Propeller Shaft Replacement in Propeller Shaft.
  3. Disconnect the transfer case switch electrical connector (2).
  4. Disconnect the encoder motor electrical connector (7).

  5. Object Number: 857301  Size: SH

  6. Remove the encoder motor bolts.
  7. Remove the encoder motor.
  8. Remove the actuator insulator gasket.
  9. If replacing the encoder motor, remove the locating pins from the old motor.

Installation Procedure

Important:

If the encoder motor is being replaced, ensure that the transfer case is in the neutral position. Manually shift the transfer case at the shift shaft, using a crescent wrench if necessary.
When installing the encoder motor, ensure that the encoder motor is indexed correctly and the motor is flat against the transfer case before tightening the bolts.
A NEW encoder motor does NOT come with locating pins.


    Object Number: 857328  Size: SH

  1. Install the locating pins to the NEW encoder motor.
  2. Position a NEW actuator insulator gasket to the transfer case.
  3. Install the encoder motor.
  4. Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

  5. Install encoder motor bolts.
  6. Tighten
    Tighten the bolts, in the sequence shown, to 20 N·m (15 lb ft).


    Object Number: 829147  Size: SH

  7. Connect the encoder motor electrical connector (7).
  8. Connect the transfer case switch electrical connector (2).
  9. Install the front propeller shaft. Refer to Front Propeller Shaft Replacement in Propeller Shaft.
  10. Install the transfer case shield, if equipped. Refer to Transfer Case Shield Replacement .

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