P-R-N-D-3-2-1 switch fails

[Mark Rinker]

2002 truck. First indication of problem was no lit gear indicator on dashboard, followed by lost 3-4 upshift functions. Only the square behind the '3' indicator would illuminate, then strange 4-3 downshifting, hanging in gears, no forward gears, etc. Progressively got worse throughout the day.

Called dealer - said it would likely be in the ignition switch. Was closer to another trusted general repair shop, they scanned it and agreed with dealers assessment, based on codes.

Replaced ignition switch, most codes were then cleared, but still didn't have 4th/5th gears and same '3' indicator lit. Replaced switch at transmission, problem then fully corrected.

My guess is the igition switch replacement was uneeded, but what was done was done at that point. If you experience this, replace the transmission switch FIRST...

[DmaxMaverick]

The NSBU (what you finally replaced) would have been my first guess. I don't know what gave them the ign switch idea....The symptoms are wrong (w/o knowing your DTC's). What color is the box they installed? Black or tan?

[Mark Rinker]

Yeah it was my first guess, too. (Although I didn't know what they were called, I had seen the switch when under the truck.) However, I was away from home and the computer to check here on the DP first, and I wasn't sure it would make it home. Sometimes speed costs money.

The DTCs indicated something in the ignition circuit - low voltage maybe? Terry is honest and I agreed with his approach based on the DTCs and the comments from the Service Manager at GM. The old NSBU switch that came out was tan. I think the new one that went in was black. Terry said something about different markings on the switches. Is there a difference?

Oh well. Could be worse than a new ignition switch at 180K. Maybe it will save me another problem down the road.

[dmaxalliTech]

Yeah, NSBU would be my first guess as well.

As for the Ign switch, they are not prone to failure, but at least you got a new one now.

[Travis Ploman]

My shift indicator starting acting up this morning. Wouldn't light under the gear selected or would intermittently even light under a gear other than that selected. Also had at least one occasion of shifting extremely hard into reverse. Doors won't unlock anymore when put into park either. Took it to the dealer and they say the NSBU is shot and they can't get the part til Tuesday. $315 installed :eek: I always thought I had 100,000 mile warranty on powertrain but they tell me it's 3/36 on the tranny. Has anyone gotten warranty coverage over 36000 on this w/o an extended warranty? Can this job be done easily for less money? Any harm in driving it until repaired?

Thanks in advance for any help!
2003 GMC D-MAX, 65000 miles

[DmaxMaverick]

......Can this job be done easily for less money? Any harm in driving it until repaired?

Thanks in advance for any help!
2003 GMC D-MAX, 65000 miles

Welcome to the Forums!

The switch (NSBU) can be had a an Allison distributor/dealer for around $60 US, and it takes less than 30 minutes to install with common tools. $315 is highway robbery!

[STPETEBLUE]

The NSBU (what you finally replaced) would have been my first guess. I don't know what gave them the ign switch idea....The symptoms are wrong (w/o knowing your DTC's). What color is the box they installed? Black or tan?X2. My shift indicator would disappear completely, or stay at the previous position when I would select another gear. The transmission would work fine, but all functions related to what gear you selected (power locks, back up lights, mirrors) acted up. Looked at the NSBU switch first. Turned out to be a short in the newly replaced radio! :eek:

[Travis Ploman]

Welcome to the Forums!

The switch (NSBU) can be had a an Allison distributor/dealer for around $60 US, and it takes less than 30 minutes to install with common tools. $315 is highway robbery!


Hey thanks! Called the Allison dealer and got the NSBU kit for $46. Off to install it this afternoon. With what seems like such a widespread problem, you'd think GM would cover this issue and not attempt to "soak" the customer with the repair price I was quoted.

Thanks for the help!

[jbplock]

Travis,

FYI .. If you haven't seen it already, here's an article in the member's area on the NSBU switch which inlcudes detailed R&R instructions.

http://www.thedieselpage.com/members/duramax/nsbu.htm

:)

[Travis Ploman]

Picked up the $46 part and it took all of 20 minutes to replace and my problems are resolved. Big thanks to this forum and it's members for saving me over 265 bucks!! :D

[Turbo Al]

I carry a spare NSBU switch in the truck -- it doesn't seem to take much to make these things flaky and I am on my third now. Takes about 12 mins to change one out.
Al

[akrockhound]

The PRNDL SWITCH IS A KNOWN ISSUE WITH AT LEAST '03 AND NEWER.

MY DEALER RECENTLY REPLACED MINE AND WAS ABLE TO COVER IT UNDER THE EMMISSION WARRANTY WHICH APPARENTLY OUTLIVES THE DRIVETRAIN WARRANTY.

[Dan Logan]

My NSBU switch has failed and I have a new one and would like some installation tips. My old switch was black, new one is tan. The new switch has a 3/16 hose barb located between the two electrical connectors. Is this a vent or some other important function? Both switches have slotted mounting holes like they can be adjusted or "Timed" to the shift shaft. It appears that the Trans. should be in neutral for installation. Anybody with experience in these issues?

[jbplock]

Dan,

This article in the members section should answer your questions .. includes installation pictures ...

http://www.thedieselpage.com/members/duramax/nsbu.htm

[Dan Logan]

Thanks to the members of this forum I was able to determine that my NSBU switch is covered under the 5yr. 100K mile emissions warranty and is listed in my warranty booklet. My servicing dealer that diagnosed the problem however, didn't tell me this. Instead they said they would be able to install a new switch for $400.00. I thought this sounded a bit too high so I declined the offer and said I would be installing it myself. The manager immidiately tried to scare me by asking how I would re-program my computer and calibrate the switch. I told him not to worry about that, I would figure it out. That led me to the internet and your forum. I didn't even go for their switch which they wanted to sell me for $189.00. My switch from Allison cost $60.00 delivered. I found the link with the installation instructions and discovered that I needed to be a subscribing member to access the page. That was an easy decision to make. I hope I will be able to help someone in the future as much as I have been helped here. Thanks again!!!!
Dan L.

[chessy56]

I've heard of the same happening on an acquaintance's 2001 Duramax. But I also heard that there was a stainless steel bracket (shield) that covers this switch- like a skid plate would. Don't know where he got it, but said it was well worth the $$$. My '01 Max hasn't had this problem yet (knocking on wood....)

Chessy56

[Inspector]

For the problem that was described the NSBU was the proper fix. I had a problem with a message that appeared that was "SHIFT RANGE INHIBIT".
The mechanic went right for the NSBU and changed it out for the updated TAN version. This didn't fix the problem. In this case they were releasing the truck to me after the NSBU switch was changed thinking that it was fixed. When the tech went to get my truck for me, on start the message reappeared. He put the Tech II on and found that the TCM was getting a low voltage through the Ign. switch. The switch was changed and I have not had another issue with that.
I also got the new updated NSBU in the process.
Denny

[madmatt]

I've heard of the same happening on an acquaintance's 2001 Duramax. But I also heard that there was a stainless steel bracket (shield) that covers this switch- like a skid plate would. Don't know where he got it, but said it was well worth the $$$. My '01 Max hasn't had this problem yet (knocking on wood....)

Chessy56

There is a shield available thru GM parts and is mentioned in a TSB. I posted the info on here somewhere and sometime ago but my searches have yeilded no results. I've installed several and they do serve their perpose well.

[Turbo Al]

The error codes continued to come up on mine untill I cycled the ignition a few times then everything was fine. It is a kick inthe pants when the error codes reapear but just keep cycling the ignition or pull the battery cables.

If your read the fine print the NSBU is not covered by the 5 year warrenty -- at least not on the 2001 model. It is specificly omitted from the warrenty -- wonder why??
Al

[mattb5150]

Hey Guys,

We recently got the wife a Certified Pre-Owned 2005 Z71 Suburban. Before we put 3000 miles on it (still in warranty) it would intermittently not go into reverse when she shifted it, took to local dealer couldn't find anything. Took it to the local trans shop, had the fluid and filter changed and they checked it over and could find nothing as well.

The other night the wife said the trans was slipping after taking off from stops signs. I drove it that night, no codes, ran good. Yesterday driving around town looking at houses, lots of stop and go, and it started slipping in 3rd gear. Had to limp it home in 2nd on the back roads. Could this be an NSBU? Any one know of TSB's for the 2005 Suburban trans, like madmatt? Any help greatly appreciated.

Matt B.

[Mark Rinker]

NSBU failed (again) today while plowing. Stopped at NAPA and picked up a $45 new one (black) and replaced the one that went just less than one year ago (tan). Started shifting hard, erratic indicator, then SES light which ended up being a TCM fault and a few other transmission related codes.

All was well after the part swap - shifting returned to normal, all gear indicators worked for about one hour with the new part and all codes cleared.

Then 'D' went away. Then 'P' and '2'. All forward and reverse functions remained normal, but the indicator has eventually gone completely blank. No codes set, no limp. (Yet.)

Truck is parked, plowing is done. There was a tiny amount moisture in the connections when replaced, wondering if this alone could be the culprit. If it had salt in it, there might be just enough conductivity to cause erratic information to the TCM. The connectors were in good shape otherwise, clean and tight. or ? The switch and connections were relatively clean and muck free, considering the rest of the snow laden truck and packed snow outside the frame rails, wheel wells, etc.

Anyone had this issue? Now I am wondering if it was the switch at all. If you read the earlier posts in this year-old thread, you can see this has been a real PITA to troubleshoot, but I am thinking that the common theme is moisture when plowing...

[Mark Rinker]

A few weeks has gone by, and the indicator/shifting issues continue.

Mostly when cold, won't get a 'D' indictor, and truck will hang in 3rd until it starts working again. Same issue has happened intermittantly with 'R' and even 'P'.

Brand new switch. Codes today were: P0622, P0700 TCM fault, ND000

I have a spare (2003?) TCM. Thinking about swapping it and seeing if anything changes...too cold to do anything with it today.

[Rendrag Farms]

A month ago, I ran into a similar issue. My truck slams into 1st and/or R; wouldn't go above 35 mph without over rev'n, and the shift indicating lights would work once in awhile. My warranty just ran out; I recently purchased a new herd of cattle and needed to transport them soon since the farmer only had enough hay to last a week longer.

I heard if there is a pin hole in your external transmission oil filter, it could cause the tranny not to shift. So, I changed my trans. oil and filter. By golly it appeared to fix the problem (except for the shift indicating lights). Fixed it enough for me to haul the herd to my farm. After I was done hauling, and parking the trailer, it started acting up again. This time, I just unscrewed the oil filter and dumped it, and screwed it back on. Again, it appeared to have fixed the problem for a week.

A week later, it started acting up again, and pulling the filter off this time did nothing. Went to a Party a few hours away, and a nephew informs me of this web site for Duramax Diesels. I did a search for my issues, and there it was. The NSBU switch.

A website was posted in where to buy the switch and pictures were offered to show exactly what to do. I followed your guys lead, and only $77 later I had my truck back up and running. However, it didn't fix everything right away. It immediately fixed the indicating light, but that's it. I forgot the posting about restarting your truck a few times. 3 times and nothing. I thought, shuck's, and was about to give up when I decided to move it down to the other driveway, when all of a sudden, the SES light disappeared and smooth shifting followed.

So, a recap of my long-winded story: Thanks to everyone here. I read the $400 horror garage stories about this switch repair, and thought it was worth changing it out myself. I first checked with the local GM dealer and they wanted $199 for the tan switch. Advance Auto said they can't get the part. So, back to your web site where I used the URL that was posted and ordered the switch and two days later, I'm good to go.

[linchhummmer]

in my 01 lb7 the backlighting quit working and would sometimes flicker and it seemed like if i pushed in on the dimer switch it would stay on

[Mark Rinker]

Replaced NBSU sourced from NAPA (black plastic variety) a few weeks back with OEM GM part. Problem solved.

Hours wasted on bad part, right out of the box...