Shift Range Inhibited

Discussion in 'GM Allison' started by BudTX, Jan 3, 2010.

  1. BudTX

    BudTX Edjumacated Redneck

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    I backed out of the 25 degree garage into 12 degree blowing snow and wind this morning, heard a slight pop (that I thought was ice) and then got the Shift Range Inhibited message on the DIC, and the bar underlining the R disappeared. I had hit the 4x4 button upon backing out to allow for better traction. If I put the truck back into 2wd it worked fine, but 4x4 would give me the same symptoms and the RPMs would increase but the truck would not move.

    I made my trip in 2wd, and tried 4wd again when I got home. It worked fine then.

    I am hoping that it was either TC drainback (having not driven the truck in 6 days), or ice on the NSBU switch from driving in the snow a week ago.
     
  2. btfarm

    btfarm Quarter Million Worth Staff Member

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    I've only seen that message once and it was completely off the wall. Sunny day about 25deg and truck had been sitting outside overnight (maybe upper teens). I had done some heavy trailering (in T/H) the eve before and after I dropped the rig in the barn I drove around front to park. Fired it up next morning, put it in reverse and got the message. Thought WTF to myself, shut it off, waited a minute and restarted. Problem over. I chalked it up to a fluke tied to the T/H circuit.
     
  3. Dad's 05 LLY

    Dad's 05 LLY Real Trucks Don't have Spark Plugs!

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    Happened to me once, too. Was parked in the ditch on a driveway at an angle, put it in drive, and that came up. Put it back in park, shut it off, turned it back on, and went fine.
     
  4. BudTX

    BudTX Edjumacated Redneck

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    It did it again this morning, trying to back out of the garage. I let it warm up a bit more, tried driving back and forth a bit, but it kept acting up so I put it in 1st and drove it back up into the garage. It only got 1/2 way out anyway.

    I need to crawl under it and see if I have the 1 or 2 connector NSBU and order one. And they are forecasting snow, 30+ mph winds and a high of 3 degrees F tomorrow. :(
     
  5. btfarm

    btfarm Quarter Million Worth Staff Member

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    While you're underneath, give the connecting lugs a good cleaning and put some dielectric grease in there. That may be your trouble.
     
  6. HemisAreSlow

    HemisAreSlow FREE!!!

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    bad neutral back up saftey switch
     
  7. HemisAreSlow

    HemisAreSlow FREE!!!

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    02-07-30-011C: Slow or No Engagement of Automatic Transmission, No Start, Blank PRNDL Display, Flashing PRNDL, DTC P0708, P0872, P0847, P0875, P1711, P1713 or U1000 Set (Diagnose Condition, Repair) - (Jun 21, 2004)


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    Subject: Slow or No Engagement of Automatic Transmission, No Start, Blank PRNDL Display, Flashing PRNDL, DTC P0708, P0872, P0847, P0875, P1711, P1713 or U1000 Set (Diagnose Condition, Repair According to Procedure)


    Models: 2001-2004 Chevrolet Silverado
    2001-2004 GMC Sierra
    with Allison® LCT1000 Automatic Transmission (RPO M74) and
    6.6L DuramaxTM Diesel Engine (RPO LB7) or 8.1L Gas Engine (RPO L18)





    --------------------------------------------------------------------------------

    This bulletin is being revised to add model years and additional model information and add graphics. Please discard Corporate Bulletin Number 02-07-30-011B (Section 07 -- Transmission/Transaxle).


    --------------------------------------------------------------------------------

    Condition


    Some customers may comment on one or more of the following conditions.

    • The PRNDL display is flashing.
    • The engine will not start.
    • The "Service Engine Soon" Indicator lamp is illuminated.
    • The transmission does not shift properly.
    • The vehicle will not move, transmission will not engage.

    Cause


    Moisture contamination within the Park Neutral Position (PNP) Switch may cause this condition. This is sometimes referred to as the Neutral Start Back-up (NSBU) Switch. On a left turn, water spray from the left front tire is directed directly at this switch. Proper installation of the "Front Shield" and "Rear Shield" are essential for proper repairs.
    Technician Diagnosis


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    This bulletin ONLY applies to vehicles equipped with a two connector PNP switch as shown above.

    A complete and through diagnosis must be performed by a qualified electrical technician to determine the cause and avoid needless replacement of good components.

    Important: The Transmission Control Module (TCM) and or the Pressure Switch Manifold (PSM) should NOT be replaced unless properly diagnosed. They are probably not the cause of the concern. It is often assumed the module is the cause of the concern when, in fact, it is another component or the wiring between the components that causes the concern.

    Important: Remember, everything starts with a properly operating Neutral Start Back Up (NSBU) switch. The NSBU switch has been incorporated into what is now called the Park Neutral Position (PNP) switch. If the PNP switch does not provide the proper voltage signal to the module indicating the transmission is in either Park or Neutral, the module will not allow the starter operation. After the engine is started, and the shift lever is moved to either Reverse or one of the drive positions, the range selected portion of the PNP switch portion provides a voltage input to the module as to what range the driver has manually selected for transmission operation. The module then controls pressures, shift points and other transmission functions based on the voltage input received from the range portion of the PNP switch.

    The technician may find one or more of the following conditions. The list of these conditions does not imply any type of frequency or order. They are random events and may occur in any order.

    • DTC P0708, Neutral start/backup (PNP or NSBU) switch
    • DTC P0847, Pressure Switch Manifold (PSM)
    • DTC P0872, Pressure Switch Manifold (PSM)
    • DTC P0875, Pressure Switch Manifold (PSM)
    • DTC P1711, Pressure Switch Manifold (PSM)
    • DTC P1713, Pressure Switch Manifold (PSM)
    • DTC U1000, Serial Data Communications
    • Blank PRNDL Display
    • Flashing PRNDL Display
    • Slow or No Engagement of Automatic Transmission


    Blank PRNDL Display
    A blank PRNDL display may indicate a condition with the PNP switch and/or one or more of the four signal circuits from the PNP to the TCM.

    Pin A, Circuit 771 (BLK/WHT)
    Pin B, Circuit 773 (GRA)
    Pin C, Circuit 776 (WHT)
    Pin D, Circuit 772 (YEL)
    Or, a blank PRNDL display may also occur if an out of line condition exists with the Serial Data Circuit (CKT 2470, yellow wire) from the TCM to Splice Pack 205.

    Diagnostic Tip


    Connect the Tech 2® to the vehicle.
    Power up the Tech 2®.
    Does the Tech 2® communicate with the TCM? If not, inspect the serial data circuit, CKT 2470 (Yellow wire), between the TCM and Splice Pack 205. Specifically inspect connector C106, a five terminal connector located below the left side underhood bussed electrical center, directly beneath the red battery cable terminal connection. Perform a mating terminal pull test on all of the terminals in this connector. Repair as required.
    Observe the Gear Selected screen on the scan tool. The following values should be shown on the Tech 2® display and the vehicle's instrument panel cluster (if equipped with the I/P display). • "8" (shifter should be in the Park position)
    • "7" (shifter should be in the Reverse position)
    • "5" (shifter should be in the Drive position)
    • "3" (shifter should be in the Third gear position)
    • "2" (shifter should be in the Second gear position)
    • "1" (shifter should be in the First gear position)
    • "0" (shifter should be in the Neutral Position)

    If the Gear Selected display does not match the shifter position in the vehicle, diagnose using one of the following methods.

    • Obtain a new PNP switch kit, P/N 29540479, from the Parts Department.
    1. Disconnect the wiring connector from the original transmission mounted PNP switch.
    2. Connect the new switch to the wiring connector.
    3. Return to Step #4 above and observe the display as you rotate the switch. If all positions indicate properly, refer to the Correction section below.
    • Use the DTC P0708 diagnostic chart in Service Information (SI) under Transmission/Transaxle/Automatic Transmission - Allison. Reference SI Document ID #769549 for the wiring schematic for this symptom.


    The PNP switch, as referenced in SI, is known as the NSBU switch in the Parts information. It is now serviced with a Park Neutral Position Switch Kit, P/N 29540479.

    Flashing PRNDL Display
    A flashing PRNDL display may be the result of incorrect sensor inputs or transmission abuse protection modes being received by the TCM. The following are some of these conditions:

    • The transfer case is/was in Neutral.
    • The transfer case is/was shifted into Neutral when the vehicle is moving.
    • A decrease of the input turbine speed was not detected when the gear selector was moved into any gear.
    • A low transmission fluid level.
    • A misadjusted PNP/NSBU switch.
    • Turbine input speed or output speed sensor failure.
    • Failures of the shift solenoids to route the transmission oil to the proper clutch assemblies within the transmission.
    • Failures of the transmission clutch packs (C1 or C5 for first gear, C3 or C5 for Reverse).
    • Failure to detect proper line pressures when a gear range is selected, which may be the result of normal maintenance such as a transmission fluid change having been completed, or the transmission pan was removed for a filter replacement or other type service.


    Transmission abuse protection modes are encountered when a customer performs one of the following types of maneuvers:

    • Shifting from Neutral to Drive/Reverse when the engine RPM is greater than 1400 RPM.
    • Shifting from Drive to Reverse when the throttle position (TPS) is greater than 25%, such as rocking the vehicle when stuck in an attempt to free the vehicle.
    • When the transmission output speed is greater than 300 RPM from attempted changes in direction such as Reverse to Drive, Drive to Reverse or Neutral to Reverse shifts.


    When the TCM encounters any one of the above conditions, the TCM will flash the PRNDL and default the transmission to Neutral. A flashing PRNDL indicates something is/was incorrect. The transmission may need the attention of a qualified service technician.


    Correction

    Disconnect the wiring harness from the PNP switch.
    Disconnect the shift linkage/cable from the shift lever at the transmission.
    With a wrench keeping the shift lever from rotating, remove the nut from the end of the selector shaft.
    Use a file to remove any burrs or raised metal where the selector lever was seated against the shoulder of the selector shaft.
    Important: If the old PNP switch will not slide from the selector shaft without the effort, the selector shaft may need to be filed to remove flaring on the end of the selector shaft. This is important, installing the new switch onto a selector shaft that has damage will cause damage to the new PNP switch.

    Remove the two bolts that attach the PNP switch and remove the switch by sliding it outward over the selector shaft.
    Make sure the selector shaft is in the N (neutral) position (using a wrench on the selector shaft flats, rotate the shaft to its furthest clockwise position and then rotate counterclockwise two detents).

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    Important: If the new PNP switch will not slide onto the selector shaft easily, the selector shaft may need to be filed to remove flaring on the end of the selector shaft. This is important, installing the new switch onto a selector shaft that has damage will cause damage to the new PNP switch.

    Slide the new PNP switch over the selector shaft with the neutral assurance bracket 920 facing outward and maintaining the correct PNP switch orientation to the selector shaft. Install and hand tighten the two PNP switch attaching bolts so that the PNP switch and bracket may be rotated within the adjusting slots with some effort.
    While holding the neutral assurance bracket in engagement with the PNP switch, tighten the two bolts that attach the PNP switch to the transmission case.
    Tighten
    Tighten the bolts to 27 N·m (20 lb ft).

    Remove and discard the neutral assurance bracket.

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    Important: Installation of the front shield and rear shields are important. Without proper installation of the shield, a return repair is probable. Follow all directions as listed on the installation instructions sheet included in the Switch kit, P/N 29540479.

    Fit the new shield onto the PNP switch so that it fits securely against the switch. Make sure this is done before reinstalling the shift lever.

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    Reinstall the shift lever. With a wrench keeping the shift lever from rotating, install the nut on the end of the selector shaft.
    Tighten.
    Tighten the nut to 24 N·m (18 lb ft).

    Connect the wiring harness connectors to the PNP switch.
    Attach the selector cable to the lever. Check and adjust if needed.
    Go back to step 4 of the Diagnostics and insure the Tech 2 readings match the shift lever positions.
    Important: Clear all DTCs before returning the vehicle to the customer.

    Return the vehicle to the customer.
    Parts Information
    Part Number
    Description

    29540479
    Switch kit, Park Neutral Position


    Parts are currently available from GMSPO.



    Read more: http://www.justanswer.com/questions...y-dash-gearshift-indicators-are#ixzz0bsGr9kCj
     
  8. BudTX

    BudTX Edjumacated Redneck

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    Thanks for the info, guys.

    In crawling under the truck and looking at the switch, it appears that I unplug the NSBU connection, remove 2 bolts, and reverse the process to install the new one, working around the front drive shaft.

    Any tips from those who have done this before?
     
  9. HemisAreSlow

    HemisAreSlow FREE!!!

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  10. btfarm

    btfarm Quarter Million Worth Staff Member

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    I remember back in the day that there were a bunch of 'bad NSBU' threads at DP. I doubt if it would be worth the time to do a search but what the hey...
     
  11. BudTX

    BudTX Edjumacated Redneck

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    I finally found a place that could order me one for $76 plus $10 shipping. It was a local bus repair garage that services Allison transmissions.

    A vendor at another site (one that I have spent over $5k with over the last several years) wanted $91 plus $15 shipping, and would not give me any consideration for a price break despite the $$$$$ that I had spent with his shop in the past. His phone clerk was not helpful at all.

    The local dealer wanted $188.

    I will post the installation results next week. I am assuming that I do not have to remove the front drive shaft to get to this; does anyone know for sure? I will be doing this without a lift. :(
     
  12. HemisAreSlow

    HemisAreSlow FREE!!!

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    i do not believe you need to
     
  13. jimburr

    jimburr New Member

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    I did mine in the driveway on a piece of cardboard, drive shaft in place.
     
  14. BudTX

    BudTX Edjumacated Redneck

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    Thanks guys. Hopefully the weather will warm up and at least get a little closer to the freezing mark when I tackle this.
     
  15. HemisAreSlow

    HemisAreSlow FREE!!!

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    o come on.....your not afraid of a little cold are ya??? I just did a valve gasket job on my old plow jeep out side standing in knee deep snow...you southern boys would love it up here
     
  16. big block 88

    big block 88 Big Block 88

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    Hows the weather doin here in KS for you Bud?? I'm lookin at -5 on a thermometer right now and it's not evenm in the wind. And why is it snowing again it was supposed to be sunny wtf??
     
  17. BudTX

    BudTX Edjumacated Redneck

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    I hear you, Blake. It is -3, snowing again, and that danged NW wind keeps blowing drifts.

    I got stuck in the snow on our unplowed gravel road today. It had drifted over about 3' high last night, and with the truck DOA I was driving our Jeep Cherokee and high-centered on a drift that was a lot deeper than it looked. 45 minutes later I was dug out and back in action, but I am still cold.
     
  18. btfarm

    btfarm Quarter Million Worth Staff Member

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    In a weak moment I'm starting to feel a twinge of 'sorry for you'...:confused:


    Ok, I'm over it! PHEW!:D

    What happened to the tractor?




    ):h
     
  19. BudTX

    BudTX Edjumacated Redneck

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    The starter groans, and when it does catch and fire it is weak and only pops once or twice. No amount of english on the choke can get it to start up.

    I suspect a bad battery behind the weak spark, as I replaced the coil and ignition late last year. The battery will not take a charge beyond 50%, so I am going to replace it and see if I can get her running again. Hopefully I will not have to pull and replace the plugs as well; the ones on these old 6v 8ns can get crudded up when the engine floods.
     
  20. big block 88

    big block 88 Big Block 88

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    Our old Ford 641 is still goin strong in this but the big issue we have is we have those stupid turf tires they suck in snow and mud. I feel like I'm ice skateing when i'm tryin to plow.
     

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