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Encoder Motor Sensor Replacement (w/ pics!!)

This is a discussion on Encoder Motor Sensor Replacement (w/ pics!!) within the Technical / Maintenance forums, part of the General Discussion category; I looked around and got the general idea of how to do this procedure because I have had intermittent issues ...

  1. #1
    Registered User hollywood_35's Avatar
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    Encoder Motor Sensor Replacement (w/ pics!!)


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    I looked around and got the general idea of how to do this procedure because I have had intermittent issues with the 4WD in my 2005 GMC Sierra with the "stellar" auto-trac. So I searched briefly and could not find anyone that did a write-up with pictures or anything. Basically, I was getting the daily SERVICE 4WD message but it would only really act up on occasion. I took it in to get codes pulled about 3 months ago when it just didn't want to make up it's mind for what drive it wanted to be in. They said it was the encoder motor sensor and it would cost 600 of my hard earned loonies to repair. I put it on the back burner since it seemed to go away temporarily. Until Murphy's law kicked in and being the crappiest snowiest day so far, it quit all together. So having it stuck in 2WD on ice and being an hour away from home going down a highway with blowing snow and drifts 2 feet high, of course it would fail. So on the way home, stopped at the friendly local GMC stealership and got the encoder motor sensor and the red rubber gasket for a grand total of around $260 CDN. I parked in the garage and let the old girl sit for a bit to drip dry and melt off most of the ice from the underside.

    !WARNING! I am by no means a certified mechanic, I am just a guy with a garage full of tools and the ambition to do things myself. I do not trust a lot of the mechanics in my city just because of how some of them do their job, I trust myself because when something goes wrong I can blame myself. Anyway this is what I did:

    It is recommended that you put the transfer case in neutral to make it easier to align the gears. However I did not have that option since it was stuck in 2WD. (always use that parking brake!!)

    Jack the front end of the truck up and support it with stands so you can safely roll around underneath it.

    Remove the 4 transfer case skid-plate bolts. I used a 15mm socket with an impact. Set that skid-plate aside and if possible, hose it off because you know there's mud on the top side.

    Get ready to drop the front driveshaft, on the yoke entering the transfer case, there is a rubber dust boot with 2 clamps. Remove the one closest to the transfer case and set aside. If you're careful and crafty you can reuse it. On the front yoke, mark the shaft's location with a paint pen (I prefer everything goes exactly where it was) and grab a 7/16" socket and undo the 4 U-joint retainer bolts. Now push the driveshaft towards the transfer case until the U-joint clears the yoke, and lower it. Pull the driveshaft forward a bit only until you can see the spline on the transfer case. Then mark it's alignment with the paint pen. Once you do that you can pull it right off and set it aside.
    **If your transfer case was in 2WD like mine, the front driveshaft will spin when trying to remove the retainer bolts. I used a chain-grip to hold it steady**

    Now that the driveshaft is out of the way, you can remove the encoder motor assembly. (At this point if you aren't sure what the encoder motor looks like, consult google) The encoder motor's wiring connector is kind of tucked up towards the top of the transfer case, and it's a doosey. If you can grab it, tug on it a bit and the connection will come free of the retainer and you'll be able to access it better. It's a stupid connector where you have to remove the grey clip and then undo it. Now that it's unhooked there are three 15mm bolts holding it to the transfer case. They're in there with loc-tite so I used and air ratchet to spin them out. You now have the encoder motor, if you haven't priced one out yet, don't drop it.


    Here is the new sensor and gasket, seems a bit over-priced. Oh wait, I got it at the stealership.


    So now you can dust and wipe it off to make sure no crap goes inside once you open it up. Clean up the black plastic plate with 4 red holes, cause it gets reused. Mark the location of the gear in correspondence with the case, just because. Lay in on the workbench with the black tube sitting vertical. Undo the 4, and only 4 outside torx screws. The 2 torx screws in the "middle" stay to keep the motor's black plastic cover in place.


    When you open it, there are two metal spacers that go on top of each gear, if they aren't on top of the gears carefully look on the inside of the case lid, they're probably stuck there. Mark the location of the big gear with the little gear before you move anything, this is crucial. Now you can remove the big gear, lift it straight up a bit, and unplug the 3 wired connector from the encoder motor sensor. Once separated from the case, the sensor just slips onto the gear, poke a screwdriver through the gear holes and get the sensor off. You now hold the very reason you can't happily operate in 4WD, isn't it sad?


    I opened my sensor up and found the reason it wasn't working, it looks like something had fallen loose inside and scratched up the important side of the sensor. A few microns of missing epoxy is the reason for a one hour white knuckle ride through deep snow.


    Anyway, place it on the gear, careful to make sure the stub on the inside of the sensor matches the notch in the gear. It's recommended that you tap the sensor in place very gently with a socket to ensure it's seated. !!When you attach the 3 wire connector to the new sensor, make sure the connector is facing the right way. It says TOP on one side!!


    The old red rubber gasket just pulls out, and the new one goes in very straight forward. I ran light oil around it on my finger just to make sure it gets a good seal.From there, it's all a matter of putting everything together exactly the way it came apart.

    Torque Values:
    - Long torx screws on the encoder motor case 3.38 Nm (30 lb in)
    - Short torx screws on the encoder motor case 2.25 Nm (20 lb in)
    - Three mounting bolts for the encoder motor to the transfer case 20 Nm (15 lb ft)

    If I left anything out, feel free to pipe up. This is my first write up so I'm sorry if it's not that precise.

    -Hollywood_35
    Last edited by hollywood_35; 01-06-2010 at 02:58 AM.
    mbullard88 likes this.

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    Registered User daved931's Avatar
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    Re: Encoder Motor Sensor Replacement (w/ pics!!)

    Cool write up
    1999 2 Door Tahoe 4x4 w/ 14 Bolt SF & TruTrac. All kinds of upgrades, SOLD 1/2012
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    2014 Silverado 1500 Z71, stock for now

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    Re: Encoder Motor Sensor Replacement (w/ pics!!)

    Maybe this should be a sticky... Just had the same problem but changed the whole encoder motor out with a good used one from my parts truck. Anyone know of an aftermarket sensor from standard or if you can find a AC Delco or Delphi sensor anywhere? Is that the GM P/N on top of the sensor? I don't see why the aftermarket wouldn't offer that for like $60...

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    Registered User hollywood_35's Avatar
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    Re: Encoder Motor Sensor Replacement (w/ pics!!)

    Quote Originally Posted by K Berg View Post
    Maybe this should be a sticky... Just had the same problem but changed the whole encoder motor out with a good used one from my parts truck. Anyone know of an aftermarket sensor from standard or if you can find a AC Delco or Delphi sensor anywhere? Is that the GM P/N on top of the sensor? I don't see why the aftermarket wouldn't offer that for like $60...
    I'm not sure, I looked for aftermarket a couple times but didn't go too in depth. I just went to the dealership because I knew they could get it immediately. Luckily they had what I needed in stock. I'm sure you could get it a lot cheaper from somewhere. I'll get the GM part numbers for both pieces and add them.

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    Registered User jimbo92's Avatar
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    Re: Encoder Motor Sensor Replacement (w/ pics!!)

    did you have to reset anything?
    78 fj40 locked with 35km2
    01 ext cab 4x4 with 4:10s

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    Re: Encoder Motor Sensor Replacement (w/ pics!!)

    I did everything i could to find the part numbers for the seal and sensor and none of the dealerships in my area would sell it. they all told me the same thing that it needs to be replaced as an encoder motor assembly anywhere from $620 to $960. I found a couple posts from other forums and found someone with the part numbers for an avalanche which should be the same 246 autotrac. I'm not positive though so i'm hoping you can check your numbers as well before I order a non-returnable part.
    Sensor is GM P/N 88962315
    Seal is GM P/N 12384990
    I hope these are the right parts. I can order them from GM Parts Direct for $83.39 shipped to my door.

  7. #7
    jo-al
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    Re: Encoder Motor Sensor Replacement (w/ pics!!)

    I bought the hole unit for about 150.00 dollars with exchange from oriellys auto parts...I know it aint gm or delco but it works great.. and i didnt have to drop the shaft to install it.

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    Re: Encoder Motor Sensor Replacement (w/ pics!!)

    Good write up, Hollywood! I could have used it a little while ago. When I had my transfer case problems, I searched thoroughly, but never found what you just provided.

    When you post your part numbers, you should also include your transfer case RPO and the New Venture Gear number, if you know it. The sensors are different for different RPOs.

    NV246 (RPO NP8) uses sensor 88962315
    NV263 (RPO NP1) uses sensor 88962313

    Cover Seal part no. for above RPOs is 12384990.

    The part number for the clamp on the prop shaft boot is 26064275.

    I have a NV246 transfer case. Like jefh64, I just replaced the whole encoder motor assembly (using GM part no. 88962314). Unfortunately, I wasn't as lucky as him with the install. I had to drop the prop shaft to do it.

    I also had to have the dealer reprogram the TCCM.

    K Berg, try gmpartsdirect.com. Even if you don't install the parts yourself, you could buy them and take them to the dealer or a garage and just pay for the labor.
    2003 GMC Yukon XL 1500 4WD SLE
    5.3L Flex Fuel Engine (Z-code, RPO L59)
    4L60-E Transmission (RPO M30)
    NVG 246 Transfer Case (RPO NP8)
    3.73 Rear Axle w/ Positraction (RPOs GT4 and G80)

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    Re: Encoder Motor Sensor Replacement (w/ pics!!)

    Thats where I priced out my parts from, I checked on a few different forums and tried really hard on the internet to dig up any info i could. I know it is the NP8 NV246. I even checked the tag on the back. When I put the used encoder on i didnt have to reprogram the tccm.

    As for the installation... I do all my own stunts :o)

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    Re: Encoder Motor Sensor Replacement (w/ pics!!)

    so did you have a service 4wd message? or why did you replace this?
    i have the light that comes on every now and then, i replaced the switch about 60k ago, and even when the light is on, all gears work, or so the switch says anyway

    2000 ECSB - Fabtech - 35" KM2 - 17" Rock Crawlers - HPP3 - Detroit


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    Re: Encoder Motor Sensor Replacement (w/ pics!!)

    I probably have a stored code but i do not have access to a TechII and my cheesy actron scanner doesn't read B or C codes. The 99 OBS doesn't have a message center. I can almost guarantee the there is a 0327 code stored. The old encoder stopped working but everything inside seems fine. The Encoder motor I put in out of my 99 Yukon parts truck worked fine for a week and now all of a sudden is having momentary problems. This one kicked into neutral from 4Hi, but works fine in 4Lo and 2wd. It periodically flashes the light and only gets stuck when shifting from 4x4 to 2wd. All the electrical connections look brand new inside and the grounds are good. I swapped in a known good switch just to see what it did and same problems. I'll take my chances on it being the sensor. They seem more common than anything else wrong with the 4wd system next to the front axle actuator which is operating fine.
    When I engage 4x4 I can feel the clunk when the front axle engages. The low range works fine too. When I took the encoder motor off I manually shifted the case to see what it did and all ranges felt fine.

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    Re: Encoder Motor Sensor Replacement (w/ pics!!)

    I had this same problem. I replaced the switch, computer and the motor. Lucky I got all of it for like $150 used but that was 30k ago. I remember that there was a tsb about the service 4wheel light coming on. It said to replace a wiring harnes that is I think $61 from the dealer.

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    Re: Encoder Motor Sensor Replacement (w/ pics!!)

    nice write up... I had a similar issue, but my 99 sierra used a different motor, so I just replaced the entire unit. This was unfortunately after I purchased the sensor and seal. Now to just find a buyer.

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    Re: Encoder Motor Sensor Replacement (w/ pics!!)

    great write up. I replaced mine last night... seems to be working ok. When I pulled the encoder motor I found it full of oil... is this normal?

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    Re: Encoder Motor Sensor Replacement (w/ pics!!)

    Bad news guys- I wasted my money on the sensor and seal from GM parts Direct... the good news is that if I ever get another truck that has this, I will have the parts in stock... My encoder motor is totally different than yours for some reason. I have an NP8 NV246 in a 1999 2500 Suburban but it must be an earlier design. Dorman has my correct encoder motor listed as Cardone PN 48105, GM PN 12474401. I guess it is a 1999-2002 design only or possibly OBS is different than NBS even though they both use the same case.
    '99 K2500 Suburban 454,4L80E,14bFF Detroit locker,dual batteries. mostly stock with 3500 springs, K&N Intake
    '84 K5 Blazer Crate 350,SM465,NP208,D44 front, 10 bolt with eaton posi rear, 4" springs with 33"s ORD Greasable bushings, shackles, some other goodies...
    2 1970 Chevelles SS396 and 454

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    Re: Encoder Motor Sensor Replacement (w/ pics!!)

    Quote Originally Posted by Mtrotter View Post
    great write up. I replaced mine last night... seems to be working ok. When I pulled the encoder motor I found it full of oil... is this normal?
    Is yours still working? Did you have to take off the front shaft? Where did you go to learn how to replace it? Did you have the "controller" reprogrammed, I saw some posts in other forums about that one should have that done as well???

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    Re: Encoder Motor Sensor Replacement (w/ pics!!)

    I got my new sensor in and tried to change it, found out that the earlier models use an external sensor. I kind of figured that. Pretty funny how my luck would have it. I have to order a reman encoder motor so I have my brand new sensor and seal up for sale in the for sale column. If anyone is interested in it, let me know.
    '99 K2500 Suburban 454,4L80E,14bFF Detroit locker,dual batteries. mostly stock with 3500 springs, K&N Intake
    '84 K5 Blazer Crate 350,SM465,NP208,D44 front, 10 bolt with eaton posi rear, 4" springs with 33"s ORD Greasable bushings, shackles, some other goodies...
    2 1970 Chevelles SS396 and 454

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    Re: Encoder Motor Sensor Replacement (w/ pics!!)

    Quote Originally Posted by K Berg View Post
    I got my new sensor in and tried to change it, found out that the earlier models use an external sensor. I kind of figured that. Pretty funny how my luck would have it. I have to order a reman encoder motor so I have my brand new sensor and seal up for sale in the for sale column. If anyone is interested in it, let me know.
    Where is it at exactly? New to the forum? How much do you want for it? What part # is yours?

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    Re: Encoder Motor Sensor Replacement (w/ pics!!)

    It is GM P/N 88962315 for the sensor and the seal is GM P/N 12384990. I'm in New York on Long Island. Shipping shouldn't be much. I posted it a few days back under electronics in the for sale section of the forum. I've been on the forum for a little over a year I guess now. I don't know the part number for the early model sensor so I'm going to have to just bite the bullet and buy the replacement encoder motor.
    '99 K2500 Suburban 454,4L80E,14bFF Detroit locker,dual batteries. mostly stock with 3500 springs, K&N Intake
    '84 K5 Blazer Crate 350,SM465,NP208,D44 front, 10 bolt with eaton posi rear, 4" springs with 33"s ORD Greasable bushings, shackles, some other goodies...
    2 1970 Chevelles SS396 and 454

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    Re: Encoder Motor Sensor Replacement (w/ pics!!)

    OK, how much do you want for it?

 

 
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