dealer said need a new tranny. Its just gonna have to sit till Ican get it built. thanks for all the help. Im glad we have this forum.

 

My 2003 GMC Duramax does the same thing. I have a good feeling it is a factory defect. Mine continues to do it and is costing me around $500 each time I take it in.

 

I don't really want to disconnect the battery because I think it will remove all the info so it can not be scanned. I am getting tired of this message. Someone has to know what is causing this problem.

 

I have the range shift inhibited problem, with the blinking R and tranny will not shift into reverse. If I can get into D it will usually go away after I drive a short distance shut it off for a few minutes then turn it back on. Sure seems an intermittent electrical ghost gripe.

Will report back when I find something definite. I wonder if my Superchip controller will give me some codes as the check engine insignia stays lit most of the time

 

They have scanned mine everytime and have come up with nothing. I think GMC needs to look into this because I heave heard of it happening to a lot of durmax trucks out there. Frustrated...I spend 4-500 dollars everytime ot happens. Ready to trade my truck for something else. That is too bad because I love my truck

 

I'm hoping it's the transmission switch on my 09 LMM. I had the same thing happen to my 05 LLY and it turned out to be the ignition switch.

This is a photo taken yesterday on my 09

 

Sweet, I will try that next time. Mine just flat shuts down and I can not go anywhere. Mine is an '03 with a little over 100k on it. I want to say after it hit 100k is when it started happening.

 

Yep



That's when mine started intermittently causing problems. Doesn't seem to screw up permanently, so as to make T/S easier. I wouldn't abandon your truck just yet. According to the threads on this subject....it's mostly the IGN switch and NSBU that seems to be the problem on the trucks from our age range. So that means a part that's less than 100 bucks I think.

 

my 09 is doing the same but only after long drives of 120 kms or more happened Saturday and when I shut it off msg came up and took few tries to get into gear then I had hard shifting from 1-2 2-3 fine on the highway, got home let it sit till Tuesday and drove like nothing happened but furthest I drove was 75 kms one way, today drove 120 kms and after I shut it off and went back same msg and even harder shifting and some slipping. off to dealer tomorrow, buddy said his did the same and it was tcm on his 2011 denali hd..

 

24 hours later and $1000 bill I have a working truck again and a new tcm... glad to have it back but boy do they take advantage 3.5 hours of labour for 1/2 hour job... ah well

thanks for all the info

 

I've been having the exact same problem with my Chevy Silverado 2500 Duramax (2005, 240k miles). It started happening about 10 days ago and is getting worse. It almost always has trouble engaging in reverse after starting the truck. Often it won't engage in any gear until I restart the engine or shift into park and let it sit several minutes until I feel it "click" and engage. Then I can shift into reverse or drive and it is fine for as long as the engine remains running. Massey, did the problem go away when the dealer fixed the ignition switch voltage issue? Anyone else figure out what the main issue is and how to fix it? My truck does the same thing as many of you describe: Upon starting the engine, the truck won't engage in reverse, the small indicator line under the "R" blinks and the message center says, "Shift Range Inhibited". Also, when it does finally engage, the transmission clearly "clicks" and catches, much like a slipping transmission would do. Any advice is greatly appreciated. Thank you all very much for sharing your knowledge and experience. I hope I can somehow return the favor in the future. My best to all of you.

 

I'm having same problem with my 2005 6.6. Have replacement nsbu input and output speed sensors still having issues on rainy days.

 

I started having minor problem getting into drive on cold mornings a few months ago. I replaced NSBU and didn't fix, I then bought ignition switch to try second easy fix. I never had check engine light come on so no codes were seen. Before installing ign.sw. I wiggled the harness wires to the TCM and other things in the engine compartment and boy did I regret that as it then screwed up my reverse as well. I installed a ground to the TCM in hopes this was the problem but it didn't help, so I wiggled wires again somewhere I then had check engine light and went to parts store and their reader showed codes P0841, P0846, P0871, & P0700 twice. I installed a new ignition switch for the fun of it and that didn't help. I'm guessing there is something up with the TCM modules and possibly the connection pins to those modules causing many of these problems. Seems kinda fishy that my problem got worse from something so minor like wiggling wires, and I doubt I'll find a wire/conductor worn and rubbing anywhere. I'm becoming more disappointed in my Duramax as I hear about so many more people having such problems

 

Deep water

The range shift inhibited devil has struck my 2003 Silverado Duramax twice!!! Each time right after I had driven through high standing water. If you drive too fast, and get water slashed up on the NSBU switch or the connector, it will act up. Mine is the original black unit, never been pulled out, so things have gotten old (seals on the connector, and shaft input to the switch). I have not had any problems since we are in the dry season here in Florence, Or. I will try to put and electrolytic grease layer all around the switch and connectors before the wet months. I have 212,000 miles on my duramax. No other issues to cause the fault to be set.

 

Really wish someone would come up with a solution to this problem. It seems to either be the ignition switch, nsbu, the TCM. I’ve changed both the ignition switch and the nsbu and nothing. Truck won’t ingage in any gear. A couple times if I rev the truck up a little in gear it will bang into first but no reverse. Aghhhhhhhhh been chasing my tail for 3 weeks now!
Fixing to continuity test on the wiring harness. Can some one show me the harness diagram from the tcm to the plug on the trans ????

 

Just changed my ignition switch, and problem appears to have gone away (need a few drives to confirm, but the truck is laden loosely with stuff that needs unloaded first). In my case, it was intermittent, with increasing frequency. Switch in my '05 was black, replacement was partly gray. Easy peasy.

+1 for ignition switch.

Though I agree: it'd be nice to find more conclusive diagnostic methods to narrow it down to one part, even if it requires digging out the multimeter to test parts.

 

My truck is flashing range shift inhibited on my dash. Took it down a min maintenance road last Tuesday night then drive it for several hours after. It didn't start flashing until I turned the truck off and turned it back on. I made it home but I can't remember what I did to get it to actually drive. When I put it in drive you feel it kick into gear but it won't go anywhere. Been parked for almost a week now. My boy says it's going to be a 4k fix! Is it something I could fix myself? I know a little about vehicles, being single now I've learned to do all my own tuneups and other small fixes on my own. Need it fixed asap...missed out on good priced hay and ropin practice yesterday. Any ideas or links that could tell me how and what to check? Thanks in advance boys!

 

You can fix it!



Mine would go clunk into drive (and drive weakly, if at all), and generally refuse to go in reverse. It got progressively worse over time, and sometimes restarting the truck would magically fix the issue (til it didn't work anymore). Replacing ignition switch definitely fixed my issue, as I drove around all day yesterday running errands in town, no issues. And that one can be done with a screwdriver and two small pokey things (nails, golf tees, hair pins; I used some small punches) to release the retaining clips on the switch itself. New AC Delco switch was $20-30 on Rock Auto. Not guaranteed, but a cheap gamble. Took me about 15 minutes, and I was lollygagging, so I'd say pretty much anyone can do that fix themselves and save some money.

I watched this video to guide me on removing the steering column cover panels and the switch:

The replacement switch body has a gray panel, the original had black. Not sure if that's relevant or not, but at least tells you if you have the factory switch in there or not, I imagine.

If you go to any auto parts store, they often will scan your Check Engine Light codes for free (I have my own scanner and phone app, but same deal): it'll mention something about insufficient voltage or pressure or something in one of the letter-coded transmission pressure sensors (sensor A, sensor E). Also throws P0700 as a general transmission controller error code. Can't recall cuz mine's working and CEL has been turned off.

To 04baby's point, I bet it's a general defect in the design of the wiring of the whole truck; any voltage sag from a worn switch or other electronic moving part in the RUN circuit might be the culprit but NSBU and ignition switch are the ones that get the most wear and tear. Just my guess as an electronics geek and car guy, but not a seasoned Duramax-specific car geek.

 

Try to replace ignition switch, NSBU. Two easy and some what cheap repairs. I think mine was the tcm. I swapped trans and t case and still have the same problem. Put a new tcm out of the truck I got the trans and t case from and all my problems went away. Sold it and bought a dodge 👍

 

Would be nice to know the year model truck they have because it's a whole different ball game changing out the switch on the older trucks.

 

Well, here we go. My 2003 GMC 2500 HD Duramax is doing the same thing. For the first time today it said shift range inhibited and I had no reverse. Also only one gear forward and it was low. Then the message changed to service brakes or something to that effect. I think I’ll start with the ignition switch first. I don’t know why, just a gamble.

 

I don’t know what the weird letters were in my previous post. My phone probably needs work too. LOL

 

If you are posting with tapatalk the ‘ is an apostrophe.

 

I’m having the same problem cleaned out this plug to the transmission and put a new Nbsu switch on and put a new ignition in and still it’s doing the same thing is there a loose wire or something bc that’s the only other thing I can think of

 

About to replace my ignition switch on my '08 LMM Chevy Express @140k miles.... What started with a bad engine bay fuse box, followed by a blown 5V cigarette lighter fuse in the cabin fuse box preventing me from hooking up a scanner... Followed by a bad EBCM that killed my entire van (pulled it out and the right diode had burned a hole through the silicone board) van started up immediately after disconnecting it... Installed new EBCM and programmed it with the latest GM software. That got my D letter to illuminate again with gears 2 and 3, still in limp mode though and park won't light up, nor will the dash register its in park. ABS was completely fixed by replacing my engine to frame ground strap with a hefty 0guage battery cable and dielectric grease on both terminals. But I'm still stuck with gears 2 and 3. Tried replacing NSBU switch and lined it up exactly with the old one. Still only get D to light up. Also replaced shift cable for good measure, nice and tight) I then checked the code descriptions with my tech2 and the last 2 codes I'm stuck with are:

P0705 - shift range sensor circuit failed and
P0751 - shift solenoid A control circuit low voltage. I've also replaced and flashed the TCM with my licensed GM MDI 2 to no avail.

I even tried to eliminate ALL variables by swapping in a new ECM with the latest GM stock calibrations since I run a custom tune for my oversized tires... No difference in vehicle performance but managed to pull some additional codes, one possibly leading directly to the ignition switch itself: P2510 - Engine controls ignition relay feedback circuit

I'm also getting some odd codes that are constant like:

P0532- A/C refrigerant pressure sensor circuit low voltage (even though I replaced the connector and carefully spliced it on with heat shrink wrap so its moisture tight)

I've also used my wiring schematics to go around the whole vehicle and scrape clean every single ground point, including the EBCM ground to frame by the driver door, adding dielectric grease afterwards and using my digital mutlimeter to test for voltage drop

I've also gone around to each connector and cleaned it with electronic cleaner and condensed air if it had way too much dielectric grease squished in to it (the EBCM one of them, Chevy replaced the connector but slathered grease on the female side instead of the male like you're supposed to, probably what caused the first EBCM to short itself out and burn a hole in the diode)

I should mention I also have excellent brand new dual AGM starter batteries, and cleaned the grounds to both of them. I even spliced in a new 0 guage positive cable to the engine bay fusebox megafuse from the starter battery so there is literally zero voltage drop at the fuses.

I also have a brand new OEM starter... The vehicle starts up like a champ, (1 second fire ups on cold mornings) warms up great and even shifts perfectly from gears 2 and 3 on first warm up...but if I drive around and take it easy for about an hour or so the shifts will get hard, the check engine light comes on and I get the shift solenoid A valve performance code. Brand new trans fluid and filter, zero metal shavings on the magnet (recently rebuilt trans 4L85E) and I even replaced shift solenoid A (the wiring is perfect) to no avail. Using full synthetic trans fluid too, its still perfectly pink, nothing burnt. Proper fluid levels.

Its got to be the ignition switch right? Its the only thing I haven't done... And I ordered a spare acdelco off rockauto in case I ever needed it... I just hope this is it because I've been tackling this for almost 2 years, even had jaws drop when I explained to Chevy mechanics what I'd done and repaired, they of course never got anywhere and gave me 50% off after admitting I've done everything they would do and that it sounds like I'm getting close.

Wish me luck guys...

Well after much frustration, cursing, and instructions for my truck that are wrong, I finally got the ignition switch back in properly aligned (2 notches over from where the instructions on alldata told me to set it) and nothing has improved. Still no park indicator, lights up in drive but throws p0705 and p0973 for low voltage to solenoid A control circuit. I repeat: a brand new TCM, NSBU switch, ignition switch, and entirely new engine bay fusebox, and brand new batteries, have not fixed the control circuit low voltage.

At this point I might just sell it.

 

Well the alldata and YouTube instructions are fucking wrong... fuck my life. Now I have to realline the ignition switch to the way it was when I pulled it out, not per the instructions. They specify having it in the off position, but having the lock cylinder in the accessory position. What the hell? They're wrong. You need to line it up, meaning the key should be in the accessory position together with the switch. So CONFUSING!!! I HATE CHEVROLET

 

07 LBZ change transmission changed transfer case changed ignition switch changed TCM changed wiring harness still says range shift inhibited anybody have an idea now what the heck this is crazy

 

Have you changed the bottom of the ignition switch? It's not the same as ignition switch.