I have codes P0700 and P0810 coming up with the CEL. Car seems to shift fine and shift to neutral in stop seems fine and smooth too.

It will cost me $115-130 (didn't mention the CEL) out the door to have the TCM updated so it won't shift to neutral automatically when stoppped because after some research that feature seems to have caused costly issues to many volvo owners. I assume they would clear the codes as well, hopefully they won't charge me something extra because of that like unnecessary diagnostics or something.

I was planning on doing a drain and fill with Ipd's kit and 12 quarts of Mobil 3309 from eBay, but should I do the software update first and see how it goes? I checked the dipstick after driving over 20 minutes and you can still see a tint of red and the level is perfect.

So do the software update first or the fluid drain and fill? Thanks.

 

Doesn't sound like the tranny at all maybe the shift module ??? It is the selector that give it it's position and return send the signal to the tcm to relay with the ecu. If your valve body is in the correct position and the module is slightly off then it could just find neutral ???. I'm just guessing. But if the tranny works fine then I would suspect the shift module. It happened to me on my old 93 ford f350 turbo diesel. The thing was just worn out could be your shifter assembly too. Being it is in drive and just makes your way to neutral. It's right next to drive
Hold your shifter firm in drive making sure it doesn't move while driving the car. There is a lock , if it's worn you should be able to move it from drive without compressing the shifter release button.
Might also get a person in the car put it in drive with BRAKE on and you manually try to move the shift module from the engine compartment. If it moves you have found the slack. Issue. It should not move to neutral

 

I'm confused. The car IS supposed to shift to neutral automatically when in DRIVE and at a stop (ie: red light). This is expected behavior and it is a feature of the car itself. The software update from the Volvo dealership would disbale this feature so that the car stays in DRIVE when at a stop (ie: red light).

UPDATE: I spoke to an employee in the dealership telling me that if I bring it by between Wed - Fri during regular business hours, he could have the foreman/overseer clear the CEL for free and do the software upgrade for $115-130 out the door. So this is what I will be doing hopefully this week and see if the codes come back or not.

 

Most owners already had the neutral stop feature disabled because it was damaging the transmission.

If you replace the fluid, you need to reset the 'new fluid' setting in the transmission software. I would do the fluid change first, then the software reset + the new fluid setting.