Hard Shift into Reverse or 1st Gear only.

tdiblair

Veteran Member
Joined
May 16, 2005
Location
CT Yankee
TDI
Passat 2005 silver Passat Sedan & 2005 Wagon Stone Henge Gray
This bang into reverse , or when I put it into drive seldom happens more than 6 times a year and is always cured when I ' reboot' the car by turning the engine off and then starting it again. The harsh shift is limited to 1st or Reverse and does not happen in any other gear. Unfortunately it came back today with something new. I noticed the Display on the Dash to tell me what hear I was in "PRD4321" went to a solid red and I could not see what gear I was in. I also got a check engine lite in the dash too. No I don't have a coding tool to read the code. I'm just wandering if others have knowledge as to what this usually comes down to like a new Transmission Shift Module which is located under the passenger seat? 2005 Passat TDI wagon with 67,000 miles on it.

Thanks,

Blair
 

thundershorts

Top Post Dawg
Joined
Jul 15, 2010
Location
west chester pa
TDI
2015 passat tdi sel premium 2015 golf s tdi gls tdi b5.5, 2002 eurovan,Peugeot 505 td,Citroen cx25 prestige
The possibility of moisture at the tcm comes to mind first, along with the elusive brown wire splice in the harness close to the tcm. Was it a high humidity day when this happened? If so it could also be associated with the multifunction switch on the trans. If you put it in tip on days when this happens, and get an erratic display, it could be that switch.
 

tdiblair

Veteran Member
Joined
May 16, 2005
Location
CT Yankee
TDI
Passat 2005 silver Passat Sedan & 2005 Wagon Stone Henge Gray
Thundershorts, glad your still around as these Passat Diesels approach 14 years old.......Yes years ago the sun roof cause moisture on the floor which didn't do the TCM any good. Dealer dried it out and it worked fine, well past the warranty....and even today a reboot with the turn off of the engine and then a restart buys me months of this hard shift into reverse and drive , only - not the rest of the gears. I imagine after 6 years the remaining moisture on the module got the best of it. What I don't get is this time the ' Check Engine' light came on - new event - and the display on the dash board indicating what gear I'm in went solid red until I did the restart the engine ' reboot' again. As to moisture , we're in a warm winter here in CT so I'd say no.
" If you put it in tip on days when this happens, and get an erratic display, it could be that switch." Thundershorts, TipTronic did not bring the display on the Dash back - only the reboot / restarting of the engine. I'm good if they replace that TCM. I know it got wet years ago and can't be trusted...but can you explain this "Splice in the brown wire" so I can pass it on to the mechanic? Did the factory just leave a partial cut in that brown wire when they made all the wire harnesses and could I be getting a little arc out of the cut insulation in the wire?
 

thundershorts

Top Post Dawg
Joined
Jul 15, 2010
Location
west chester pa
TDI
2015 passat tdi sel premium 2015 golf s tdi gls tdi b5.5, 2002 eurovan,Peugeot 505 td,Citroen cx25 prestige
In the harness that connects to the tcm, inside the harness covering, about 8 to 10 inches from the plug is a stamped splice. its not visible without cutting open the harness. The brown wires are grounds from the tcm and as I remember end up grounding to a stud in the right kickout panel. The splice rots away and causes problems such as you describe. Also dissemble the the actual tcm plug itself and check for corrosion.
 

tdiblair

Veteran Member
Joined
May 16, 2005
Location
CT Yankee
TDI
Passat 2005 silver Passat Sedan & 2005 Wagon Stone Henge Gray
Thanks for the ' splice' location and description.....I'm thinking the once wet TCM from the classic sunroof drain clog years back should be replaced and maybe the Multi Function switch on the tranny (if a cheap part). The disappearing display on the dashboard is a new event and as I drove away I did not feel the Auto Transmission change gears. I realize remote forum diagnostics is close to impossible. But I'm willing to replace both the TCM & MFS since they are 13 years old and if the prices are reasonable. I realize the Mult Function Switch may or may not help my Display on the dash as to which gear I'm in from going solid red and making my gear selection a un-readable display. You have pointed out the problem could be coming from 3 isses....1) the spice in the brown wire or corroded plug to the TCM 2)the TCM itself or 3) Multi Function Switch. I'm just thinking they are all 13 years old and I have some long drives coming up. If the TCM and MF switch both relatively cheap , I'm going to replace them. Is replacing them simply unplugging the old units and plugging in a new TCM and MFS , with the battery to the car dissconected or is it more involved?

Thanks Thundershorts,

Blair over in CT.
 

thundershorts

Top Post Dawg
Joined
Jul 15, 2010
Location
west chester pa
TDI
2015 passat tdi sel premium 2015 golf s tdi gls tdi b5.5, 2002 eurovan,Peugeot 505 td,Citroen cx25 prestige
replacing these units is not cheap and will not in all likelyhood fix the problem. The rotten splice is a known problem and is relatively easy to fix.
 

StevePD

Member
Joined
Jul 9, 2009
Location
EastPA
TDI
2005 Passat Wagon TDI,115k ,2006 NB TDI,30k
Mr.Blair , I'm currently experiencing the same symptoms as you are. The TCU is ok, brown stamped splices inside rubber boot ok, two taped splices under the door sill have been fixed and am now awaiting a used neutral safety switch from vwztips and I'm off to Hevster for the replacement. I'm sure this is the fix, I'll report back with the results. IIRC a new TCU is around $1000 and a new NSS about $275 :eek:.
 

imo000

Top Post Dawg
Joined
Dec 13, 2005
Location
Cambridge
TDI
2009 M-B ML320 Diesel & '05 Passat TDI Manual 5-Speed
I have a TCU that's left over from the manual conversion. If you need it let me know and we'll work out a deal.
 
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