2004.5 Duramax LLY Allison P0846

[4RunnerGuy]

I have this code. The fluid level was low enough that the Shift Range Limited was displayed on the DIC.

No messages/cell were displayed while driving. There were also no clunks, catastrophes, or other.

The truck sat for a few days while I worked coolant line issues.

Is it possible to get this code because of a wire in the external harness that's rubbed through the insulation or is broken? The internal harness was replaced less than 50k miles ago.

Is it more likely the pressure switch is the issue?

 

[fl0w3n]

Luckily I’m a mind reader so I know you’re talking about an Allison behind a Duramax, because you didn’t mention that anywhere.

Read through the Allison legend Mike L helping this guy diagnose the same thing and do what he says. Good luck.

P0841-p0846

I'm getting these two codes shortly after the truck is started and rand for 10 seconds, changed the pressure with with a known good one out of my running 03' seems to only have 5th gear as it will roll 70 on the lift with out shifting and no reverse. Called yah mike no reply yet. this is a valve...

www.duramaxdiesels.com

 

[4RunnerGuy]

Edited and thank you.

 

[Rttoys]

Read through the Allison legend Mike L helping this guy diagnose the same thing and do what he says. Good luck.

P0841-p0846

I'm getting these two codes shortly after the truck is started and rand for 10 seconds, changed the pressure with with a known good one out of my running 03' seems to only have 5th gear as it will roll 70 on the lift with out shifting and no reverse. Called yah mike no reply yet. this is a valve...

www.duramaxdiesels.com

sadly he passed away a little over a year ago. Dude was a wealth of knowledge.

 

[4RunnerGuy]

sadly he passed away a little over a year ago. Dude was a wealth of knowledge.

Agree. I've read many of his posts. I didn't realize he passed, just not much recent activity.

My truck has 340k. I've ordered the pressure switch and will be dropping the pan to R&R that.

Rttoys I thought I read you saying your truck was for sale. Please pm me, I may be interested.

 

[fl0w3n]

sadly he passed away a little over a year ago. Dude was a wealth of knowledge.

Damn really? That is a big bummer. I stopped hanging around the forum when I sold my last lb7 and I know he sold the shop off to another great builder that I can’t recall.

I don’t recall if he had health issues? Or maybe it’s a case of the guy retires and shortly after with nothing to live for anymore passes away

 

[Rttoys]

Rttoys I thought I read you saying your truck was for sale. Please pm me, I may be interested.

will do

 

[Rttoys]

I don’t recall if he had health issues? Or maybe it’s a case of the guy retires and shortly after with nothing to live for anymore passes away

I read on dieselplace he died of the cancers, so maybe retiring was to take care of that. I lost track of the diesel world after dp sold to the Canadians. I was out of the trend anyways and just using my truck for hauling and daily use.

 

[Projectjunkie]

If it comes down to a tcm I have a couple spares I'd sell reasonably

 

[Rttoys]

If you need genuine Allison parts, I found this site that has a ton of stuff. I bought my Allison harness and filter about a year ago from them.

https://www.dieseldash.com/s/

 

[4RunnerGuy]

*Update

It turns out the pressure switch was the issue. Electrically it was fine, but loose in its "socket". That makes sense in hind sight, as there were some inconsistent/intermittent down shifts occasionally.

 

[Projectjunkie]

*Update

It turns out the pressure switch was the issue. Electrically it was fine, but loose in its "socket". That makes sense in hind sight, as there were some inconsistent/intermittent down shifts occasionally.

Where was the switch located?

 

[4RunnerGuy]

I replaced this manifold, mounted to tge

bottom of the valve body.