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4 Codes in Tranny

L

lonewolf

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Okay I have an 02 2500 HD Duramax Allison Tranny. It has been setting for a couple weeks and I go out this morning to drive it to work. I crank it up let it run for 5 to 10 minutes go out to leave put it in R and nothing pull it in D nothing. I go to work come home pull the codes and I get P0842, 0870, 0875,and 0700. I crank it up and it goes in and out of gear moves both ways. Now I need to know can I drive it like this or not I have reset the codes but I do not want to do anymore harm if possible. Oh also I pull a 35ft 5th wheel camper weighing in at 12,500lbs so before I start pulling it I better find out if it is okay.
 
Look up for the codes is above under the DTC tab. That might tell you more. The 0700 code is just the trans telling the MIL light to turn on. I sure wouldn't go very far without getting it sorted out. When was the last spin on filter change? Or fluid change. Sorry I don't know more about the trans.

Sent from my SCH-I535
 
Last filter change was about 2yrs ago. The thing was fine when I parked it never had any problems before this. Like I said when I came home and tried it it was just like new so I am as puzzled as a bed bug. She only has 139,000 on it and has always pulled fine.
 
Sounds like the converter drained while it sat but you ran it for awhile so that's not it. I had that happen once a few years ago and it never set a code or came back. In any case you need to put a new Allison filter on it. Drive it for a few days and see what happens. AS LONG AS THOSE CODES DON'T TELL YOU SOME DEVASTATING THINGS. I haven't been anywhere that I can look them up. Just on my phone.

Sent from my SCH-I535
 
What Mike said. Codes are scary though and the fact that it wouldn't move forward or reverse. Look up what the codes mean.
 
It could also be a bad NSBU. Since this is an 02, they had the early style NSBU with 2 plugs and gave quite a bit of trouble. The codes are for the pressure switch manifold sensing valves being stuck on. If the NSBU tells the TCM the wrong info, it could interpret that as a stuck valve.
 
So can I take it to a shop to have the codes pulled out of the ecm or sense I cleared them will they still be in there? I will drive it tomorrow and see what happens. Thanks for all the replies and help.
 
Damn... I completely forgot about the NSBU on 01 & 02s. That's a real likely cause of your codes. IIRC it's pretty easy to change the external ones like yours.

Sent from my SCH-I535
 
It is atatched to the shift shaft on the drivers side of the trans. The old style failure prone switches were black, most of the new ones are tan(but I have heard some are black now).
 
THEFERMANATOR said:
It could also be a bad NSBU. Since this is an 02, they had the early style NSBU with 2 plugs and gave quite a bit of trouble. The codes are for the pressure switch manifold sensing valves being stuck on. If the NSBU tells the TCM the wrong info, it could interpret that as a stuck valve.
Click to expand...

btfarm said:
Damn... I completely forgot about the NSBU on 01 & 02s. That's a real likely cause of your codes. IIRC it's pretty easy to change the external ones like yours.

Sent from my SCH-I535
Click to expand...

Good call on the NSBU switch. They were prone to fail due to moisture issues. They were externally mounted on the 02's. The newer, 2006's, I think are now inside the Allison. I think the replacement NSBU's took care of the problems. :thumbsup:

I got this from the Merchant Automotive site:

wwwdotmerchant-automotive.com/p-1658-allison-nsbu-switch-2001-2004.aspx

One of the most common problems with the Allison transmission is failure of the Neutral Safety Back Up switch.

Some of the symptoms of failure include but are not limited to:

No start condition
Gear shift indicator on dash not following properly
Trans stuck in limp mode or fail safe
DTC's set indicating pressure switch codes

This switch easily installs with just common hand tools.

How does it work and why does it cause my transmission not to shift?


The vehicle is equipped with a column type shift selector. In addition to the column shifter, another component associated with the shift selector is the Nuetral Safety Back Up (NSBU) switch mounted on the selector shaft of the transmission. The NSBU switch transmits selector position information to the TCM. The NSBU 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 TCM so that certain vehicle control functions can be coordinated with the position of the shift controls. The neutral signal output of the NSBU switch is typically used as confirmation that the transmission is in NEUTRALor PARK before the engine starter is engaged.

Common trouble codes associated with NSBU failure include :
DTC P0708, Neutral start/backup (PNP or NSBU) switch
DTC P0847, Pressure Switch Manifold (PSM)
DTC P0872, Pressure Switch Manifold (PSM)
DTC P0875, Pressure Switch Manifold (PSM)
DTC P1711, Pressure Switch Manifold (PSM)
DTC P1713, Pressure Switch Manifold (PSM)
DTC U1000, Serial Data Communications
Blank PRNDL Display
Flashing PRNDL Display


Slow or No Engagement of Automatic Transmission

The reason that PSM codes may set is that the NSBU switch and the internal PSM switch "look at each other" and "compare readings" Basically, the NSBU switch lets the TCM know what gear position that you, the driver, have selected. The PSM has the job of telling the TCM what gear the transmission is in based on hydraulic inputs. If the data received from the PSM and the NSBU do not agree, the above mentioned trouble codes may set. The NSBU is subject to water contamination and will allow the switch to give faulty readings.
 
Thanks guys so if it is a black switch then more than likely it is an older one so I should change it out if it happens again??
 
I would change it now as it will fail again and you don't want it to be while;e you are on the road somewhere. Do it while you are in control.
 
Marauderer said:
I would change it now as it will fail again and you don't want it to be while;e you are on the road somewhere. Do it while you are in control.
Click to expand...

:agreed: What Barry said. Did you get a bunch of snow and slush up in there before you parked it? That's a known problem for the external ones.

Sent from my SCH-I535
 
That could be it then. Drive it for a few days and see what comes up. I'd be seeing if I could find a good price on a new switch. Rockauto maybe. Check for a discount code in the Deal finder section below.

Sent from my SCH-I535
 
lonewolf said:
Oh also I pull a 35ft 5th wheel camper weighing in at 12,500lbs so before I start pulling it I better find out if it is okay.
Click to expand...

Good to see you around these parts again my friend...it looks as if Ferman and a few others have you on the right track...While I have never replaced a NSBU on my truck, I did have to replace the whole trans after a few years from putting too much power to it. but the new SunCoast trans came with the new style switch so mine never really had a chance to fail...
 
DON'T waste your money on a cheapo from ADVANCE or some place. Buy it from an ALLISON dealer. The ALLISON switch is teh same as one from GM, but it is less than half the cost. The problem is the early ALLISONS used the same switch as the 4L60E/4L80E used. It worked fine for them as all it did was tell the cluster what gear you are in, but in the ALLISON it tells the TCM what gear you have selected. The switch was prone to moisture intrusion, and any slight variation in it's output and the TCM freaks out. ALLISON has a revised switch, and GM sells the same one. But GM marks it up almost 200% and resells it(sort of like how spin ons cost $8 from ALLISON, but list for $51 from GM).
 
Okay guys very helpful info we have a dealer about 10 miles from here so I will give them a call. I guess I can give them my VIN and they can find out what I need?
 
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