Range Shift Inhibited issues - Chevy and GMC Duramax Diesel Forum
04.5-05 LLY Duramax Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission, Etc.

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post #1 of 3 (permalink) Old 01-23-2020, 07:12 PM Thread Starter
Join Date: Jan 2020
Location: Kansas City
Posts: 1
Range Shift Inhibited issues

I can use all the help I can get on this one. Beating my head against the wall at this point.

2005 GMC 2500 6.6 Diesel

### 1/18/2020 @ 8am (16 degrees snow & ice)
* Truck has sat since 1/10/2020. Drove around 40 miles in the snow on the that day.
* Started truck, transmission selector (underscore under gear) not present. Put in drive started up the driveway. Lost power half way up. Reverse not present, only 1 gear.
* Upon restart truck showed “Range Shift Inhibited”
* Check engine light was on and code read “P0700” Malfunction with Transaxle Controls.

### 1/20/2020 @ 4pm (36 degrees, sunny)
* Truck didn’t move from driveway over night due to no available reverse gear.
* Checked all connections to the TCM to determine if a pin had slipped out. Looked fine.
* Purchased Ignition Switch and NSBU Controller.
* Changed out Ignition Switch
* Truck started, Check engine light went off.
* All gears were available and no warning lights.
* Took truck for test drive. Out of driveway, 300 yards, shifted to second, maybe third gear. Truck lost power ABS & Brake light came on and displayed “Service Brake System” on dash.
* Limped the truck into a place to turn around, put truck in 1st gear and slowly drove back to house.
* Truck did not show a check engine light so no code was present.

### 1/21/2020 @ 3pm (33 degrees, rainy)
* Started truck to check if anything had changed. Exhibited same scenario.
* Note: parking brake had been pretty bad. Every once in a while I had to engage and release the brake because it had fallen in to the engaged position but the brake were so bad it didn’t actually engage. This made the “Brake” light go right off.

### 1/22/2020 @ 5pm (Truck was in heated garage all day, 72 degrees)
* Purchased and installed rear brake pads
* Drivers side rear was down to metal.
* Passenger side rear needed to be changed but not terrible.
* Both front brakes looked almost perfect.
* All rotors looked and felt fine. No vibrations or groves ever.
* Started truck, “Service Brake System” still read out on display.
* Check engine light illuminated with code: P0802 - Transmission Control System MIL Request Circuit/Open.
* Cleared Code. Restarted. Check engine light came back on. Same code.
* Drove about 300 ft to park it and I am observing hard shifting when going from park to reverse to drive. This has not been observed before.

### 1/23/2020 @ 4:00 (Truck in heated garage)
* When first started just the “Service Brake System” was showing, No gear indicator but no “Range Shift Inhibited” or check engine light.
* Cleaned ABS sensors on driver front. Didn’t show signs of any issues.
* Cleaned and lubed parking brake on passenger rear. Notice it wasn’t returning to an open state. I could motivate it by tapping it back in place with hammer/screwdriver. Left in fully open state, did not clear “Service Brake System”
* When restarting the truck, “Range Shift Inhibited” returned as well as the Check Engine light. Code was P0700- Malfunction with Transaxle Controls.
* Reverse was not available. Drive was underpowered as well as 1st.
* Replaced NSBU controller.
* No change. Cannot remove truck from garage due to no Reverse.

2005 GMC 2500HD
Duramax 6.6 LLY
Stock with K&N Air, Airbags, Trailer Brakes.
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post #2 of 3 (permalink) Old 01-23-2020, 08:51 PM
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Join Date: Aug 2009
Location: Berryton, KS
Posts: 1,472
At a minimum, you need to get the truck scanned, need B, C, P, and U codes. Make sure your batteries are fully charged. Detach and clean all the battery terminals, and all the battery cable positive ends, and all the negative ends, and the Alternator cable as well. Find out where the main grounds are for the engine, likely under that front crossmember under both radiator sides, you can get wring diagrams from GMUPFITTER.COM under the bode builder section, specifically look for ELEC manuals in their own section. Having a sound electrical system is a GREAT IDEA, for many reasons, all the time.

There are lots of posts about similar problems so spend some time on the net and see what you can find. Having the DC codes will be a big help and a likely to identify where the problem is. I suspect that the problem is somewhere in the wire bundle from the trans into the engine bay. But that's just a wild guess.

Ron Nielson
2008 Silverado LT, CCLB, Edge Insight CTS
2009 Arctic Fox 29-5T, Silver Fox Edition, Onan 3600 LPG generator
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post #3 of 3 (permalink) Old 01-23-2020, 10:10 PM
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Join Date: Nov 2009
Location: Indy OR 7S5
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My LLY would get "range Shift Inhibited" codes when it rained. Only happened a couple of times but I cleaned all the TCM related connector contacts and that seemed to fix it. Been over 6 years ago, NSBU switch was replaced when the trans was rebuilt about a 5 years ago.

2004.5 GMC SLT 4X4 CCLB LLY Ally, some mystery stuff, trans by Mike L, Magnaflow DP, Ride Rites, LBZ turbo inlet mod, AD II 165, po' man CAI, HIDs, stock height, Cognito tie rods, Bilstein 5100s, Isspros, H2 wheels with Toyo OC 285-70-17s, B&W turnover & Companion, Prodigy P3, dog snot on windows......

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