I put the truck into 4WD and it worked and when I put it back to 2WD it had a message service 4wd so I brought it to dealer and they tell me there is a short in encoder motor and that would be about $900 to replace. NOW it works so should I just let it be and ignore the message or what. it has 44,000 miles on it so I feel if it needs replacing Chevy should cover since it is implied that an encoder motor should not go at this low miliage. Thoughts please.;)

Sorry but forgot to ask the question of if there are ANY TSBs on the emcoder motors and if so please I need the number and when it came out etc please. my dealer service dept would not tell their own mother if there were a TSB.
They have on the manifest that I got a "Courtesy Vehicle" but I paid $47 for the rental and when asked if Chevy was going to be billed for the "Courtesy Vehicle" as well as having me pay for it and he said it is an automatic printing on manifest. YA right!

What year is the truck?

ya, need year and actual code pulled.

My truck is a 2003 I do not know the code and do not believe that I have it on the manifest that they gave me after I came back for the truck but I suppose could go over there and find out if they do not know then they can pull it again right?

I had an 03 Avalanche that they reprogrammed twice and never fixed and my 04 Trailblazer does the same thing, they claim theres never a code.
I think there was a TSB about the encoder motor and grounding ?

Look in "TSBs" guys...the topic right below this one. Search the topic for "encoder"....

mine went at around five k miles..blew up on the hiway after i brought it in for 4wd service lite twice..needless to say i was just a little pissed. theres a tsb on it..go after them for it.
i would also believe 900 bucks is a bit much..

The encoder motor itself is in the 800 range, then labor would put it at 900

dmaxallitech,
the code i am told is C0327 but it took them over 2 days to call me back with the answer so not sure they gave me the code because that is the encoder motor short or if it really pulled that code but it what I am being told by the Service Director.
The question is also, Am I damaging anything driving with it with this code. It only comes on with the messsage "Service 4WD" after I have been in 4WD and switched it back to 2WD. It seems to switch back to 2WD fine.

DTC C0327 with or without Additional DTCs Setting - keywords 03-04-21-001D 126 226 246EAU 263EAU #PIP3061E - (Nov 1, 2005)
DTC C0327 with or without Additional DTCs Setting
2004-2006 Buick Rainier

2003-2006 Chevrolet Avalanche, Silverado

2003-2006 Chevrolet Suburban, Tahoe

2002-2006 Chevrolet Trailblazer

2002-2006 GMC Envoy

2003-2006 GMC Sierra, Yukon, Yukon XL

2002-2004 Oldsmobile Bravada

with Four Wheel Drive (4WD) Only

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 with 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.


Refer to published service procedures for diagnosing DTC C0327 which includes basic diagnostics i.e.:


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 underhood 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.
Additional Information: Ground Locations

TCCM Ground: G110.
TCCM Ground for the Mode Switch: G203.
Note: If there are no other component issues that share the same ground (example: On-Star 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.
For "T" trucks with 126 and 226:

Refer to published service procedures for diagnosing DTC C0327 which includes basic diagnostics i.e.:
Visually check the TCCM wiring harness for pinched/chaffed concerns.
Check the pin/terminal fit at the encoder motor, connector C101, TCCM and underhood relay center.
Check the TCCM, body, chassis and engine ground credibility (Refer to published service procedures for ground locations). 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.
If DTC C0327 sets when making a shift into 4 HIGH only (226 Transfer Case) or during a slip event (126 Transfer Case, 226 transfer case in auto 4WD); inspect the Transfer Case fluid for contamination. If fluid is contaminated remove the Transfer Case and inspect for mechanical concerns.

Additional Information: Ground Locations


TCCM Ground: G201 (part of Splice Pack SP201)
TCCM Ground for the Mode Switch: G102
If no concerns have been found with the above checks, replace the encoder sensor.
Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.



GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
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4WD Switch Indicator Lights Flashing, 4WD Inoperative, DTCs C0327, P0500, P0836, P1875 Set (Replace Encoder Motor Sensor, Reprogram TCCM, Inspect Front Drive Axle Engagement Sleeve for Damage/Repair) #03-04-21-001D - (Dec 4, 2003)

</TABLE>4WD Switch Indicator Lights Flashing, 4WD Inoperative, DTCs C0327, P0500, P0836, P1875 Set (Replace Encoder Motor Sensor, Reprogram TCCM, Inspect Front Drive Axle Engagement Sleeve for Damage/Repair if Necessary) 2003 Chevrolet Avalanche, Silverado, Suburban, Tahoe
2003 GMC Sierra, Yukon, Yukon XL
with 4WD and Electric Shift or Active Transfer Case (RPO NP1 or NP8)
This bulletin is being revised to update the Diagnosis and Correction Information and to change two part numbers. Please discard Corporate Bulletin Number 03-04-21-001C (Section 04 -- Driveline/Axle).
<A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1410278&psdid=297&evc=sm#ss1-1410278">Condition

Some customers may comment that the Service 4WD light is on, the 4WD system is inoperative, the 4WD switch indicator lights are blinking or that a grinding noise is heard from the front axle.
<A href="http://service.gm.com/servlets/BlobShtml?ShtmlFile=1410278&psdid=297&evc=sm#ss2-1410278">Service Diagnosis

Technicians may find DTC C0327 in the Transfer Case Control Module (TCCM) and/or DTC P0836 in the Transmission Control Module (TCM) and/or DTC P0500 and P1875 in the Powertrain Control Module (PCM).
It is possible that the module may be in a mode that will not allow any shifts or updates for the software or calibrations. If this occurs, the TREC fuse (in the engine compartment) must be pulled and reinstalled after 30 seconds. This should allow further operation and service of the system. If a C0550 code is found, this is an unrelated concern and SI diagnostics should be followed for this concern.