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My 2007, GMC Sierra 2500HD classic keeps getting the Range Shift Inhibited on start up. I'm assuming it's electrical. The dealership charged me over $400 and couldn't even find the problem. So I went ahead and bought a diagnostic tool.

What happens is this:

I start up the truck and sometimes I can't shift into gear and I get the "Range Shift Inhibited" error message. I let the truck run to build up the batteries. I shut down the truck once the volts are up to 14. I then erase the codes, and after that I'm generally good to go.

The batteries are less than 1 year old and are Optima style, high end batteries. Both have been independently tested and are fine.

P0700 Transmission Control System (MIL Request)
P0757 Shift Solenoid ‘B’ Stuck On
P0761 Shift Solenoid ‘C’ Performance or Stuck Off
P0659 (ACTUATOR SUPPLY vOLTAGE 1 (HSD1), HIGH )
P0848 Transmission Fluid Pressure Sensor/Switch ‘B’ Circuit High
P0877 Transmission Fluid Pressure Sensor/Switch “D” circuit Low

As mentioned earlier, once the voltage is up, I clear the codes and the truck drives wonderfully. What causes the solenoid to stick and is that a job I can perform? I know many people suggest the NSBU, but on the LBZ it's internal and I've heard they rarely go.

My truck seems to run fine, but there is some electrical glitch that causes everything to go haywire. As a side note, the alternator does seem to be charging, so I don't think it's that. Any suggestions would be greatly appreciated. Is this a major issue?
 

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My 2007, GMC Sierra 2500HD classic keeps getting the Range Shift Inhibited on start up. I'm assuming it's electrical. The dealership charged me over $400 and couldn't even find the problem. So I went ahead and bought a diagnostic tool.

What happens is this:

I start up the truck and sometimes I can't shift into gear and I get the "Range Shift Inhibited" error message. I let the truck run to build up the batteries. I shut down the truck once the volts are up to 14. I then erase the codes, and after that I'm generally good to go.

The batteries are less than 1 year old and are Optima style, high end batteries. Both have been independently tested and are fine.

P0700 Transmission Control System (MIL Request)
P0757 Shift Solenoid ‘B’ Stuck On
P0761 Shift Solenoid ‘C’ Performance or Stuck Off
P0659 (ACTUATOR SUPPLY vOLTAGE 1 (HSD1), HIGH )
P0848 Transmission Fluid Pressure Sensor/Switch ‘B’ Circuit High
P0877 Transmission Fluid Pressure Sensor/Switch “D” circuit Low

As mentioned earlier, once the voltage is up, I clear the codes and the truck drives wonderfully. What causes the solenoid to stick and is that a job I can perform? I know many people suggest the NSBU, but on the LBZ it's internal and I've heard they rarely go.

My truck seems to run fine, but there is some electrical glitch that causes everything to go haywire. As a side note, the alternator does seem to be charging, so I don't think it's that. Any suggestions would be greatly appreciated. Is this a major issue?
did you ever figure this out or get it it resolved?
my truck just stated doing this

i get
P0659 (ACTUATOR SUPPLY vOLTAGE 1 (HSD1), HIGH
 

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My 2007, GMC Sierra 2500HD classic keeps getting the Range Shift Inhibited on start up. I'm assuming it's electrical. The dealership charged me over $400 and couldn't even find the problem. So I went ahead and bought a diagnostic tool.

What happens is this:

I start up the truck and sometimes I can't shift into gear and I get the "Range Shift Inhibited" error message. I let the truck run to build up the batteries. I shut down the truck once the volts are up to 14. I then erase the codes, and after that I'm generally good to go.

The batteries are less than 1 year old and are Optima style, high end batteries. Both have been independently tested and are fine.

P0700 Transmission Control System (MIL Request)
P0757 Shift Solenoid ‘B’ Stuck On
P0761 Shift Solenoid ‘C’ Performance or Stuck Off
P0659 (ACTUATOR SUPPLY vOLTAGE 1 (HSD1), HIGH )
P0848 Transmission Fluid Pressure Sensor/Switch ‘B’ Circuit High
P0877 Transmission Fluid Pressure Sensor/Switch “D” circuit Low

As mentioned earlier, once the voltage is up, I clear the codes and the truck drives wonderfully. What causes the solenoid to stick and is that a job I can perform? I know many people suggest the NSBU, but on the LBZ it's internal and I've heard they rarely go.

My truck seems to run fine, but there is some electrical glitch that causes everything to go haywire. As a side note, the alternator does seem to be charging, so I don't think it's that. Any suggestions would be greatly appreciated. Is this a major issue?
Did you ever figure out problem
 

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Check for good power/ground supply to the Allison controller. As long as that isn’t an issue, and the connection/terminals at the controller are good then it needs a new controller. Common issue.
 

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This happened to mine last month, I replaced the TCM even though dealer mechanic wanted to open tranny and change selector switch and check valves. I ordered a TCM for $351 from a dealer about an hour away and paid the tech to flash it to my truck. Local dealer wanted $561 for part. Been running great for 3 weeks. Here's the thread on my truck issue Need help quick, Truck won't go
I know I am reply to a response from 5 years ago, I am fighting this too, and well every tech I spoke to says it is not the TCM! I think I need to try this. My issue is getting a P0761 SS3 stuck off when below 30 degrees, fluid is good, mid hot range at 170 degrees. shifts good otherwise, when cold, it can be shifting fine and trans warmed up, then get the shift range inhibited and lock into 4th gear. when warm. NO issues.
 

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The TCM monitors inputs from several onboard systems to operate the transmission properly. If the TCM receives an input that s far enough out of range to affect transmission operation, the TCM will enter Transmission Abuse Protection Mode.

In this mode, the TCM can inhibit engagements into drive and reverse and any or all shifts, depending upon what caused the TCM to enter this mode.

What Is the TCM Monitoring?
The TCM monitors inputs from numerous sensors from several onboard systems to control the transmission operation. These sensors are:

Crankshaft (CMK) and CamshaftPosition (CMP) sensors (figures 1 and2) for engine RPM.
Throttle Position Sensor (TPS)or Accelerator Position Sensor(APPS; figures 3 and 4) forengine load.
Manifold Absolute Pressure(MAP) or Barometric Pressure(BP) sensors (figure 5) also forengine load.
Engine Coolant Temperature(ECT) sensor (figure 6) andTransmission Fluid Temperaturesensor (TFT), located in the pressure switch manifold (PSM).
Neutral Safety Backup Switch(NSBU) (figure 7) or Park/NeutralPosition (PNP) switch.
Input Speed Sensor (ISS/TSS;figure 8).
Output Speed Sensor (OSS).
Transmission Fluid PressureSwitch (PSM; figure 9).
Transfer Case Position sensor or switch (figure 10).
Let s look at each of these inputs to determine how the TCM uses them to control the transmission operation.

Crankshaft and camshaft position sensors Provide the TCM with engine RPM signals, which it uses to calculate TCC slip.

Throttle position sensor or accelerator position sensor Provide the TCM with engine load signals to calculate line pressure rise and shift timing.

Manifold absolute pressure and barometric pressure sensors Provide the TCM with engine load signals for calculating line pressure rise and shift timing.

Engine coolant and transmission temperature sensor Provide the TCM with temperature signals to allow it to determine actual operating temperatures of engine and transmission.

Neutral safety backup switch or park/neutral position switch Provide the TCM with signals to indicate selected gear range.

Input speed sensor Provides the TCM with a signal to measure the rotating speed of the turbine shaft, from which it can calculate transmission RPM and slip.

Output speed sensor Provides the TCM with a signal it can use to determine vehicle speed and calculate transmission slip.

Transmission fluid pressure switch manifold Provides the TCM with signals for monitoring clutch engagement and shift timing.

Transfer case position sensor or switch Provides the TCM with a signal to identify transfer case range.

Now let s discuss how each of these inputs can cause the TCM to inhibit transmission operation. When the TCM inhibits the transmission operation, you may notice the PRNDL display flashing on and off or display Gear Inhibited or Shift Inhibited. These conditions can cause the TCM to inhibit transmission operation.

High engine RPM on engagement Check engine RPM while shifting into gear. If engine RPM exceeds idle specifications, the TCM will keep the transmission in neutral. Check CMK and CMP inputs and idle speed adjustment; repair as needed.

High throttle or high torque on engagement If the throttle or accelerator position sensor signal exceeds 25% during transmission engagement, the TCM will keep the transmission in neutral. Check sensor input signal to TCM at idle; repair as needed.

Erratic input speed sensor signal If the TCM receives an erratic input speed sensor signal during engagement, the TCM will keep the transmission in neutral. Check input speed sensor signal; repair as needed.

Erratic output speed sensor signal If the output speed sensor signal is erratic or over 300 RPM during engagement, the TCM will keep the transmission in neutral. Check the output speed sensor signal;
repair as needed.

Erratic neutral safety backup or park/neutral position switch signals If the TCM receives an erratic signal from the neutral safety backup or park/neutral position switch, it ll keep the transmission in neutral. Check the switch signals at TCM, check wiring and connections, and check for water contamination in the neutral safety backup switch; repair as needed.

Erratic pressure switch manifold signals If the signal from the
pressure switch manifold is erratic, the TCM will keep the transmission in neutral. This may be caused by low fluid level, valve body problems, a faulty pressure switch manifold, or problems with the wiring or connections; repair as needed.

Low transmission fluid temperature If the transmission fluid temperature sensor signal indicates the transmission temperature is below -49 F (-45 C), the TCM will keep the transmission in neutral. Verify the transmission temperature. Check the transmission fluid temperature sensor circuit, wiring, and connections; repair as needed.

Transfer case in neutral when shifting transmission into gear If the transfer case control system indicates the transfer case is in neutral while shifting the transmission into gear, the TCM will keep the transmission in neutral.

If it indicates the transfer case was shifted to neutral while driving, TCM will wait until the vehicle output speed drops below 300 RPM to shift the transmission into neutral. Check and repair transfer case input to TCM as needed.

Transmission slip If TCM receives a signal that the transmission is slipping, it ll prevent the transmission from shifting into that gear range. Check transmission operation; if it seems to be working properly, check the appropriate sensor inputs. If the transmission is slipping, repair as needed.

Well there you have it: the most likely causes and possible cures for the most common problem plaguing the Allison LCT1000 transmission: inhibited shifts or gear ranges. With a better understanding of how the Allison LCT transmission group operates, you should have no problem keeping those trannys rolling
 

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Thanks so Much!

  • MEMBER
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The TCM monitors inputs from several onboard systems to operate the transmission properly. If the TCM receives an input that s far enough out of range to affect transmission operation, the TCM will enter Transmission Abuse Protection Mode.

In this mode, the TCM can inhibit engagements into drive and reverse and any or all shifts, depending upon what caused the TCM to enter this mode.

What Is the TCM Monitoring?
The TCM monitors inputs from numerous sensors from several onboard systems to control the transmission operation. These sensors are:

Crankshaft (CMK) and CamshaftPosition (CMP) sensors (figures 1 and2) for engine RPM.
Throttle Position Sensor (TPS)or Accelerator Position Sensor(APPS; figures 3 and 4) forengine load.
Manifold Absolute Pressure(MAP) or Barometric Pressure(BP) sensors (figure 5) also forengine load.
Engine Coolant Temperature(ECT) sensor (figure 6) andTransmission Fluid Temperaturesensor (TFT), located in the pressure switch manifold (PSM).
Neutral Safety Backup Switch(NSBU) (figure 7) or Park/NeutralPosition (PNP) switch.
Input Speed Sensor (ISS/TSS;figure 8).
Output Speed Sensor (OSS).
Transmission Fluid PressureSwitch (PSM; figure 9).
Transfer Case Position sensor or switch (figure 10).
Let s look at each of these inputs to determine how the TCM uses them to control the transmission operation.

Crankshaft and camshaft position sensors Provide the TCM with engine RPM signals, which it uses to calculate TCC slip.

Throttle position sensor or accelerator position sensor Provide the TCM with engine load signals to calculate line pressure rise and shift timing.

Manifold absolute pressure and barometric pressure sensors Provide the TCM with engine load signals for calculating line pressure rise and shift timing.

Engine coolant and transmission temperature sensor Provide the TCM with temperature signals to allow it to determine actual operating temperatures of engine and transmission.

Neutral safety backup switch or park/neutral position switch Provide the TCM with signals to indicate selected gear range.

Input speed sensor Provides the TCM with a signal to measure the rotating speed of the turbine shaft, from which it can calculate transmission RPM and slip.

Output speed sensor Provides the TCM with a signal it can use to determine vehicle speed and calculate transmission slip.

Transmission fluid pressure switch manifold Provides the TCM with signals for monitoring clutch engagement and shift timing.

Transfer case position sensor or switch Provides the TCM with a signal to identify transfer case range.

Now let s discuss how each of these inputs can cause the TCM to inhibit transmission operation. When the TCM inhibits the transmission operation, you may notice the PRNDL display flashing on and off or display Gear Inhibited or Shift Inhibited. These conditions can cause the TCM to inhibit transmission operation.

High engine RPM on engagement Check engine RPM while shifting into gear. If engine RPM exceeds idle specifications, the TCM will keep the transmission in neutral. Check CMK and CMP inputs and idle speed adjustment; repair as needed.

High throttle or high torque on engagement If the throttle or accelerator position sensor signal exceeds 25% during transmission engagement, the TCM will keep the transmission in neutral. Check sensor input signal to TCM at idle; repair as needed.

Erratic input speed sensor signal If the TCM receives an erratic input speed sensor signal during engagement, the TCM will keep the transmission in neutral. Check input speed sensor signal; repair as needed.

Erratic output speed sensor signal If the output speed sensor signal is erratic or over 300 RPM during engagement, the TCM will keep the transmission in neutral. Check the output speed sensor signal;
repair as needed.

Erratic neutral safety backup or park/neutral position switch signals If the TCM receives an erratic signal from the neutral safety backup or park/neutral position switch, it ll keep the transmission in neutral. Check the switch signals at TCM, check wiring and connections, and check for water contamination in the neutral safety backup switch; repair as needed.

Erratic pressure switch manifold signals If the signal from the
pressure switch manifold is erratic, the TCM will keep the transmission in neutral. This may be caused by low fluid level, valve body problems, a faulty pressure switch manifold, or problems with the wiring or connections; repair as needed.

Low transmission fluid temperature If the transmission fluid temperature sensor signal indicates the transmission temperature is below -49 F (-45 C), the TCM will keep the transmission in neutral. Verify the transmission temperature. Check the transmission fluid temperature sensor circuit, wiring, and connections; repair as needed.

Transfer case in neutral when shifting transmission into gear If the transfer case control system indicates the transfer case is in neutral while shifting the transmission into gear, the TCM will keep the transmission in neutral.

If it indicates the transfer case was shifted to neutral while driving, TCM will wait until the vehicle output speed drops below 300 RPM to shift the transmission into neutral. Check and repair transfer case input to TCM as needed.

Transmission slip If TCM receives a signal that the transmission is slipping, it ll prevent the transmission from shifting into that gear range. Check transmission operation; if it seems to be working properly, check the appropriate sensor inputs. If the transmission is slipping, repair as needed.

Well there you have it: the most likely causes and possible cures for the most common problem plaguing the Allison LCT1000 transmission: inhibited shifts or gear ranges. With a better understanding of how the Allison LCT transmission group operates, you should have no problem keeping those trannys rolling
"
"Erratic pressure switch manifold signals If the signal from the
pressure switch manifold is erratic, the TCM will keep the transmission in neutral. This may be caused by low fluid level, valve body problems, a faulty pressure switch manifold, or problems with the wiring or connections; repair as needed."

Thanks So much! It ended up being pinched wires by the frame from the TCM, re-routed brand new ones loomed, all good NOW! I wish people would have just posted this when someone must have come up with the solution when it is moisture/temp related! Your knowledge is super, are you a trans tech?
 
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