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Eric
Eric, ASE Certified Technician
Category: Chevy
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Experience:  11 GM years experience
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Silvarado Duramax-Allison 2004 Sometimes will not shift into

reverse; may or may not... Show More
reverse; may or may not refuse to shift into D 3 2 1 -- receive message "range shift disabled" when I try reverse (no message in D 3 2 1). Problem comes and goes. Once it's in gear, it drives normally.
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What is the outside temp at the time?
Customer reply replied 6 years ago.
Outside temp at time of malfunction around 40 degrees Farenheit (overnight temp around 20). Today problem occurred with engine and transmission almost fully warmed up.

The only time this message would come on during normal condition (without a actual problem or malfunction with the trans) are

- Shifting the trans from park or neutral to drive or reverse while the engine is not at idle.

-Shifting the trans from drive to reverse or reverse to drive while under load throttle around 25% (as if you were rocking the truck to get unstuck)

-if the transfer case is in neutral or the tcm thinks its in neutral (has there been a service 4wd message?)

-shifting from reverse to drive or drive to revers while still moving, driveshaft moving more than 300rpm in either direction.

- low atf fluid or lack of prime (have seen one case of the pump would loose prime after sitting, had to replace trans pump)

- low atf temp below -49 deg f

 

Problems that could cause this message to come up as a result of a malfunctioning part and would require repair. Would have to go to dealer to check for DTC's

 

- Low voltage on a ecm circuit. there is a info bulletin out this #pip3413a

-turbine or output speed sensor failure

-park neutral switch out of adjustment

- there is also a clutch failure, but you said it woks fine after initial gear select so thats probably not the case.

 

Customer reply replied 6 years ago.
Is there a place where I can see #pip3413a?
Engine was at idle, not under load, 2wd or 4wd indicators were lit and I tried switching back and forth, atf fluid level is middle of range when warm and idling, atf was near normal running temp.
Interesting you should mention park neutral switch. The only other reference to "shift range disabled" I found on the Net suggested that could be the cause.
What do you think of tsr #02-07-30-011C which includes observation "the vehicle will not move, transmission will not engage?" It suggests moisture in park neutral switch thrown by left front tire (I have been driving in snow/ice and ambient temp never gets high enough to really dry anything out).
I will be taking the truck to a local mechanic (I live in the boonies). He can read the codes. Will he know where to look for the park neutral switch?
If it is moisture in the switch, could it perhaps be dried out or must it be replaced?
How does one "adjust" a park neutral switch?

The PI involves taking a scan tool while the problem is happening and watching the voltage on the tcm, if you have no other problems except the trans this may not be it.

 

As far as the bulletin #02-07-30-011C this involves the park/neutral switch with 2 connectors. The switch is on the drivers side of the trans you will see the shift cable attached to a leaver in front of it. if you have a switch with one connector this dose not apply. the switch is sealed and cant be taken apart. as fas as adjusting it, to do this correctly there is a special tool to hold the switch in the N position. A new switch will have a similar tool installed.

 

I would have the shop check for any codes that may help narrow down the search for the problem part, depending on his scan tool he can observe the voltage as in the PI and also check the park switch data to see if it matches where the shifter really is. The key is checking all this data while the problem is happening.

Customer reply replied 6 years ago.
OK,

So next steps are check codes, check voltage, check park switch data, hopefully while the problem is happening.

Since the problem has only happened twice, it may be hard to replicate at the shop. If we can't find anything wrong, what do you think of replacing the park/neutral switch and seeing if that helps? Is that too long of a shot? It's really a bummer to be stuck in neutral while blocking traffic.

The codes should point us in the rite direction, and if they have anything to do with the switch it may not be a bad idea.

Customer reply replied 6 years ago.
Thank you.