I have an 01 duramax and a few days ago the light for the shifter only would work in reverse in reverse and third. it would work in the other gears fine but would not show them. now it still only shows reverse and third but no matter what drive gear(overdrive,3rd,2nd,1st) it goes into third and wont go out. reverse still works fine. The CEL came on and flashed these two codes at me p0700 and p0708. Anybody got any ideas.

Possibly a bad NSBU.

That would cause it to only go in reverse and third too

P0700 Is a code for MIL light requested

p0708 Is a code for transmission range curcuit high input.

Circuit Description
The installation of a transmission-mounted neutral start/reverse signal switch is required. This switch, commonly called a "Park/Neutral Position switch", mounts directly onto the transmission housing from the outside and detects the angular position of the shift selector shaft. This position is communicated to the Transmission Control Module (TCM) so that certain vehicle control functions can be coordinated with the position of the shift controls. The Park/Neutral Position (PNP) switch has redundant circuitry to alert the TCM in the event of a single wire or switch failure.
The neutral signal output of the PNP switch is typically used as confirmation that the transmission is in neutral before the engine starter is engaged. The PNP switch is interfaced to the starter circuit with weatherproof electrical connectors. The reverse signal provision may be used to activate vehicle back-up lights and/or reverse warning devices.
DTC P0708 is a type A DTC.


There was a service bulletin about water contamination of the switch. They installed a new switch and a redesigned sheild to prevent water from entering the switch.

If you have a scan tool I can send you the dagnotic chart. Send me a pm if you would like the chart.

Hope this helps.

I'm suffering from the same symptoms. Same codes thrown.
I ordered a new NSBU switch from Eric and hope to have it within the next day or two.

Re: the P0700 code - what is a MIL light?

thanks.

mine is doing the same thing with the light being on in certain gears.then i parked and i came out and started my truck and the service engine light came on and it will only start out in 2nd gear and will not shift out of 2nd gear.and when i go to park it makes a hell of a clanking sound.any ideas thanks,jeff

I'm suffering from the same symptoms. Same codes thrown.
I ordered a new NSBU switch from Eric and hope to have it within the next day or two.

Re: the P0700 code - what is a MIL light?

thanks.

Malfunction Indicater Light or the check engine light.

Vmax4911 - same thing as the rest of us. Order the NSBU switch from Eric at Merchant Automotive. (one of the supporting vendors) His screen name is Dmaxallitech. $65 + shipping. Easy self-installation. Complete how-to in the do-it-yourself section.

P0700 Is a code for MIL light requested

p0708 Is a code for transmission range curcuit high input.

Circuit Description
The installation of a transmission-mounted neutral start/reverse signal switch is required. This switch, commonly called a "Park/Neutral Position switch", mounts directly onto the transmission housing from the outside and detects the angular position of the shift selector shaft. This position is communicated to the Transmission Control Module (TCM) so that certain vehicle control functions can be coordinated with the position of the shift controls. The Park/Neutral Position (PNP) switch has redundant circuitry to alert the TCM in the event of a single wire or switch failure.
The neutral signal output of the PNP switch is typically used as confirmation that the transmission is in neutral before the engine starter is engaged. The PNP switch is interfaced to the starter circuit with weatherproof electrical connectors. The reverse signal provision may be used to activate vehicle back-up lights and/or reverse warning devices.
DTC P0708 is a type A DTC.


There was a service bulletin about water contamination of the switch. They installed a new switch and a redesigned sheild to prevent water from entering the switch.

If you have a scan tool I can send you the dagnotic chart. Send me a pm if you would like the chart.

Hope this helps.

IS this the NSBU switch?

Yes it is the NSBU switch

Yes it is the NSBU switch


Good I just changed it. Got from a Allison Transmission place in town, paid $55.10. Dealer wanted over $125 for it. Why are dealerships allowed to bend people over this way?

Anyhow, drove the rig around the block, light still on, drove another 2 miles, stopped got me a natty light. get back in lights off and shifting like a charm.. appreciate the help. this website has saved me some money.

The dealers get thier switches from Allison. They have to make a mark up on the parts also.

I glad that your truck is fixed.

My "02 Silverado started having the same symptoms last night. :mad:

I called the local dealer and they wanted $205 for the switch. :eek:

My "02 Silverado started having the same symptoms last night. :mad:

I called the local dealer and they wanted $205 for the switch. :eek:

DSW---check your messages

Man, my switch took a dump this weekend too! Nothing lights up and I maybe get R and 3. It's the black one. Guess I'll be ordering up one.

My truck is doing the same thing. Took into the dealer, then checked this site. Dealer wants 212$ for the sw and 520$ total to change it out. I have also seen a thread on here that says it is suppose to be an "Emissions" warranty part? Anyone had luck with that?

My truck is doing the same thing. Took into the dealer, then checked this site. Dealer wants 212$ for the sw and 520$ total to change it out. I have also seen a thread on here that says it is suppose to be an "Emissions" warranty part? Anyone had luck with that?

For comparison's sake, an Allison shop, Stewart & Stevinson, in Denver charged me $200 total to replace it. $65=tax for the part and about $120 in 1hr labor and shop fees. Took the mech just over 1/2 hr laying in the parking lot on a creeper. Not too difficult to do, have to drop the front driveshaft to get at it easily and get it adjusted right when bolting back up. I was on the road when mine failed, so it was money well spent to not have to ***** around with it, but in your own garage it's probably only a 2-3 beer job and some common hand tools.
$500 at the dealer?? What a ripoff.

My truck is doing the same thing. Took into the dealer, then checked this site. Dealer wants 212$ for the sw and 520$ total to change it out. I have also seen a thread on here that says it is suppose to be an "Emissions" warranty part? Anyone had luck with that?

Yes, two weeks ago, me and a buddie of mine, both within 2 days of eachother. Go to the NSBU warrenty infor at the top of the OEM Tranny page. It is all spelled out there. Just to be sure its a 6 year 100,000 mile. So if your over miles then it won't be covered.

Thanks for all the info, Dealer told me yeah its warranty part but is 5 yr 100K miles. They said my truck went out 12/07/06 just last month. Took my truck to the local Allison dealer 49.36 for the SW and 41$ for the 1/2 hr to put it in. 93$ out the door installed at the Allison dealer, Boise GM dealer wanted 520$ to do the same deal. Oh the Sevice manager was going to knock off 50$ if I had it done that day. Glad I came to this site before I heard what he had to say. Anyone in the Western IDAHO area that needs the work done let me know I will point you in the right direction. Thanks to every one else that replied.

so i got the switch changed and had the codes read and cleared, and i had the p0700. I got it cleared, so why is it back on?? Am I going to have to go to the stealer??