Transmission Code "Unknown DTC29"

Post by **boosted5cyl** » 12 Mar 2012, 11:38

98 V70 T5...
Having some weirdness with our transmisson when the fluid is cold. The 1-2 shift is extremely prolonged, will really only shift when I lift off the gas, 2-1 shift is very harsh and sometimes when I move off the line it behaves as its in neural for a second and pops into gear.

Once the fluid warms up all is good. Now Last week the MAF started acting up and it is currently disconnected, however the behavior appears to be the same regardless of the presence of a MAF signal or not. Also, we had to disconnect the MAF a couple of years ago when the original went south but the transmission did not behave this way. Occasionally the transmission arrow will blink but that only happened once or twice in the last couple of weeks. I pulled the transmisson codes with VOL-FCR and got "Unknown DTC29". i cant find anything on this when I search online and none of the the AT codes listed in VADIS start or end with "29"!. I cleared the code last night and did a drain and fill so I will see if the code come back.
The fluid was a little murky but no signs of burning or anything like that. Any thoughts on what might be going on when the fluid is cold in this thing?

Post by **regent** » 12 Mar 2012, 15:41

Are you using the full lcensed version or a demo; the latter cannot decipher all codes.
It is best to talk to the car with a Volvo proprieatery software. An indie with VIDA would do that for less than what the stealership charges ($90-ish), and you will skip the guesswork.

Post by **precopster** » 12 Mar 2012, 19:25

Had the same problem on my wife's '95 850 and though it gave no codes it responded to rowing the gearlever back and forth. The fluid was new in our case. It ONLY ever did this when cold which may have been interpreted as cold fluid.

This led me to the PNP which after a good clean and resurfacing of the angled copper contacts (which should be straight) it
never gave us any grief since and reverse light is restored also.

The Autel MS509 gives accurate codes for these cars except that it doesn't work for SRS codes.

Post by **boosted5cyl** » 29 Mar 2012, 15:15

OK update on this. Haven't really delved too deep but for sure its something to so with the 1-2 solenoid. When cold it takes a long time to shift up to 2nd from first, depending on throttle position and air temp (yes really). I can help encourage it to shift to second by lifting off the gas, but sometimes unless its above 3500RPM or even more it will still stay in first for quite some time.
I can use the "w" button while I'm in 1st to get it to go into third 3rd without hesitation. The clunk I am feeling when I move off from a stop seems to be a 2-1 shift. For some reason, when cold its not shifting down to 1 until I start to move again.

Once the fluid warms up a little, it works just fine. On colder days (30-40s) it can be a few miles, warmer days (60+) a mere few blocks before its a happy camper.
The VOL-FCR I'm using isnt really trial or full, so to speak.

Any thoughts on a "sticky" 1-2 solenoid when cold?

Post by **jblackburn** » 29 Mar 2012, 15:17

I had problems with my 4th gear from a bad solenoid.

Switching to Mobil-1 synthetic ATF helped immensely for a while; it stopped dropping out of gear on hot days.

Post by **boosted5cyl** » 16 May 2012, 12:43

following up on this. So the issue persists of course. I have not done a fluid flush and am somewhat on the fence in that regard anyway, with so many miles im a little worried I might nuke the clutch linings with new fluid's detergents. With ambient temps now up a bit bad behavior stops much earlier in a typical drive cycle, but still I need to fix this. I can drive around it and "coax" it to change gear when I want, but the wife isnt doing so good.

So, where is a good source for the solenoid(s)? I guess its a good idea to replace all of them while I'm in there? Another thing I am wondering is if the issue is moreso a sticky piston rather than tired solenoid. Should I try to replace or at least inspect & clean the piston for the 1-2 shift circuit? I was considering doing the whole valve body but at $600, nuts to that. I'd rather to a 5 speed swap

Post by **jblackburn** » 16 May 2012, 12:46

Is your time more valuable than your money, or do you not mind wasting a few hours on it?

I went with used solenoids from a known working, low-mile junkyard transmission (83K mile vs my 193K at the time). Worked flawlessly since, and it was $40 for all 3 of them vs $125 for each.

If that hadn't worked, I would have gone the route of putting in a new transmission as well.

http://www.fcpeuro.com/products/volvo-a ... s2-6843783

Post by **boosted5cyl** » 16 May 2012, 13:15

Thanks for the link. Ouch! $126. I thought there were in the $40 range. Hmmm. Time is valuable, but I could afford to kill a day from a weekend on it. Really wanna 5speed this thing though

Post by **precopster** » 16 May 2012, 17:50

Still sounds like it COULD be PNP switch contacts. Have you had them out for a clean? Lotta work to swap solenoids as opposed to a PNP clean!!

I always go for the easy/cheap solutions first before delving into the fantastic/expensive/laborious ones.
Might be worth a try.

Post by **boosted5cyl** » 17 May 2012, 08:39

I can't see how the PNP switch would be related to this but its worth a try I guess.... I'll report back when I get a chance to do it.