AT trans will not engage in any gear

[jv_atc]

Dear Audizine,

2005 A6, 4.2l will not engage in any gear. A slight growl was heard upon start up today. At the moment, the only code is p1624, and while the engine idles very well, holding steady at 720rpm, there is a slight vibration in the car. While idling, there is some occasional chatter coming from under the car, the transmission area. I also noted some idle roughness upon decelerating in park, going from about 1500rpm to 720rpm.

I recently completed the chain job and the car drove for two runs before this occurred.

Thank you to the two that offered suggestions in my previous tcm post.

Anyone with knowledge of this?

Thank you.

[95blkmax]

Did you do just the upper tensioners or the full chain? Wondering if the transmission was removed or not basically... If it was removed, do you recall properly torquing down the flexplate-to-torque converter bolts?

I've seen people that completely forgot to put them on and somehow the car engaged in low rpms, but in higher loads the flexplate spun free of the TC and it was dead in the water (often time causing damage to the flexplate and TC). Engine would still idle but you'd hear the flexplate smacking/ and rubbing against the face of the TC.

The only other thing i can think of is if the TC wasn't properly seated into the inputshaft (or if it popped off slightly while bringing it up into place to bolt it to the engine... which can happen).

[sswari]

The only other thing i can think of is if the TC wasn't properly seated into the inputshaft (or if it popped off slightly while bringing it up into place to bolt it to the engine... which can happen).

And can be expensive, as you will crush the seal and or pump.

Seems to me, if you were able to drive it for any distance, and it was acting fairly normal, the TC would have to be connected properly. Assuming you had to pull the trans.

[jv_atc]

I replaced all 4 chains and all tensioners, guides... The engine and trans was removed and then separated. I recall attaching the tc to the plate upon reassembly, but don't remember what I torqued it to. It's hard to imagine that I didn't torque it, but it's possible.

Your suggestions make sense, in particular, the tc did not seat on the shaft properly. Is this circumstance consistent with the fact that there is no specific codes? Kinda makes sense...

Looks like the trans needs to come out. Are there specific things, aside from the plate, that I should be looking for?

I very much appreciate your advice and any other information. Thank you.

[sswari]

If I recall, there is very little room for the bolts to back out, if you did not get them tight so I would be more worried about the crushing of the pump and or seals. I don't know if there would be codes, but probably. Not having the TC seated correctly (in any transmission) could be a big deal. Dropping the trans is a interesting task. I would probably start, just checking if the TC and plate are connected. If your 05 is anything like my 06, To do that, you will have to remove the passenger side motor mount to get the starter out. There is no way around this, trust me I tried. It is not hard, just daunting. You may need to pick up a few extensions to reach up to the bolts.

[sswari]

jv_atc, is you motor code a BNK by any chance?

[jv_atc]

Yes, it is a BNK

[sswari]

Yes, it is a BNK

Did you pull the motor? Did you do the chain swap? Any chance you did a write up?

[95blkmax]

I don't think so brother. This really sounds like a purely mechanical deal.

One thing I'd do if you have the means to is get all 4 wheels up in the air, get under it, and with a mechanic stethospcope (or a screw driver to your ear), have someone turn the engine on and put it on D and just probe around the bellhousing to confirm that the noise you're hearing is in fact coming from the bellhousing area. If confirmed, then your problem is in there

[jv_atc]

Update... I replaced the trans filter and no difference... The car will not engage in any gear. The plate appears function and intact. We then scanned the car using vcds, resulting in:

tcm code 004- no signal/communication
p1624- mil request signal active
p1602- voltage too low
p1626- missing message from tcu
p1653- please check dtc memory of abs controller.

I'm not sure if the abs code is related in the same manner as the other codes are related. It appears as if the rattle is coming from above the pan. Maybe a result of the existing codes. I have read suggestions about a faults shift sensor or tcm.

Does any of this make sense to anyone?

[jv_atc]

sswari, yes we did pull the motor, and changed all 4 chains, guides, tensioners..., no write up, trust me, I'm a rookie, just trying to learn and get my car going

[jv_atc]

Plea add... The vibration/roughness at engine idle appeared to be absent after at filter swap and scan

[jv_atc]

sswari, did you have to support the engine from the top when you pulled the starter?

[sswari]

sswari, did you have to support the engine from the top when you pulled the starter?

jhv_atc, I supported it from the bottom. It would most likely be better to do it from the top. Dropping the Trans from the bottom was rather intimidating at first. Once I realized that it really is pretty much like any other car (Just a lot tighter) it really wasn't that bad.

I am also trying to remember if the exhaust has to come loose, and I am thinking it does.

[95blkmax]

Have you double-checked the electric harness going to the transmission to make sure all are tightly in place? Just based on the codes you are getting it seems that the car's computer is having trouble communicating with the TCU

[sswari]

Have you double-checked the electric harness going to the transmission to make sure all are tightly in place? Just based on the codes you are getting it seems that the car's computer is having trouble communicating with the TCU

I was thinking the same thing, check both ends of the harness.

[jv_atc]

I have plans to get the car on a lift this weekend. I will check the resistance from/near the TCM. I'm still trying to locate the opposite end, somewhere near the end of the harness. Should I also be checking voltage? Anyone have any resources for images or diagrams on the TCU? Engine code BNK.

[mkv]

Based on those codes above, I think there is an electrical connection issue to the trans. The vehicle is unable to communicate withe the TCU, and it should very definitely be able to do that.

I assume you have a 6HP19A in there. Audi and ZF did a change to the solenoids on the 6HP19A at some point, which went from 3 blue, 3 yellow, 1 black, to being 1 blue, 5 yellow, 1 black. The result was that you would have no drive if the TCU wasn't powered and functioning (it changed the logic of the shift solenoids). It was done as a anti-theft measure, so that if one started the engine with a hacked ECU, the TCU wouldn't engage any drive and you couldn't drive it away.
Thus since you have no comms with your TCU, you have no drive.

Hopefully it is a connection issue and not an issue with the TCU itself. I assume you reconnected all the earth straps to the engine when you reinstalled it?

Mark

[95blkmax]

On my car, there was a big harness plug (maybe 3" wide so a crap-ton of pins) that sits just over the bellhousing at around the same level as the base of the oil filter housing. I actually had to disconnect this plug in order to remove the OFH as it's support bracket uses one of the bolts that mount the OFH to the back of the engine. Check that one and a few other small ones that are there and go down towards the bellhousing/ sides of the transmission tunnel.

[jv_atc]

Update 9.18

Pulled the starter to check the plate... All appeared well... function, torqued... Checked the trans plug at the trans for power, good there. Also checked for resistance between the female pins on the plug based upon parameters found on alldata. The resistance was high and inconsistent among pairs and I will verify this again and post findings.

The tcm is not under the passenger carpet as described by many others. On this vehicle, 05 A6 4.2, 6hp19/bnk, it is behind the passenger air bag. I'm planning to access that after I record the trans harness resistance.

Any direction regarding troubleshooting the tcm is welcome. More to follow.

[mkv]

Update 9.18

Pulled the starter to check the plate... All appeared well... function, torqued... Checked the trans plug at the trans for power, good there. Also checked for resistance between the female pins on the plug based upon parameters found on alldata. The resistance was high and inconsistent among pairs and I will verify this again and post findings.

The tcm is not under the passenger carpet as described by many others. On this vehicle, 05 A6 4.2, 6hp19/bnk, it is behind the passenger air bag. I'm planning to access that after I record the trans harness resistance.

Any direction regarding troubleshooting the tcm is welcome. More to follow.

On a 6HP19 the TCM is inside the transmission, attached to the mechatronic unit. It's not a separate unit like in a C5 A6, which uses a 5HP.

[sswari]

On a 6HP19 the TCM is inside the transmission, attached to the mechatronic unit. It's not a separate unit like in a C5 A6, which uses a 5HP.

Yep, what mkv said.

[jv_atc]

Thank you mkv and sswari!

I'm just now reading your post, after pulling the glove box to get a look behind the dash. I can't imagine how or where the tcm would fit, yet, alldata shows the tcm at the end of the front passenger pilar, in the upper right corner of the dash. I just couldn't see it with the complexity of components, it would require pulling the dash to get a clear view, which I don't plan on doing at this time. I will trust you guys.

Please allow me to introduce the fact that I am a diy'er and not an auto mechanic by trade, just doing my best to learn along the way and all of your guidance is much appreciated.

Update 9.19
I found 2 sources for ohm readings at the external trans (external regulator solenoid) plug. The basic assumption here is that the information I found is valid. One source is Alldata and the other is from the online Audi workshop manuals - not my exact model available so I selected the closest I could find.

Here are my findings...
Ohms (from alldata)
Pins 12 to 2 = nothing, should be 55-65
Pins 16 to 3 = 122.8, should be 55-65
Pins 16 to 7 = nothing, should be 55-65
Pins 12 to 11 = nothing, should be 4.5-6.5
Pins 16 to 15 = nothing, should be 55-65

Online manual, again not my exact car model
Pins 2 to 6 = 54.6, should be 60-72

From what I have been able to determine, it may not be the tcm, rather something is completely fried, which I don't believe as I should still get some ohm values, more likely, something is unplugged or blown. I am basing this on the absence of resistance among the pins leading to the trans.

Will you please offer your interpretation of the above circumstances/ohm readings? Please kindly be reminded that the car ran well until the second test drive. Thank you!

[95blkmax]

I think you are right in thinking that if the circuit is closed, some resistance should be read, yet there isn't. So that would point to the circuit being open somewhere upstream.

Besides the connector you are touching now, is there anything other connector that you may have messed with during removal? Maybe a ground cable for the harness that isn't attached. Another option would be a blown fuse related to the TCM. I've never had to look for it, but if the PCM has a power relay and fuse, I assume so does the TCM. So that's something you can look into as well (funny thing is though, if you DO find a fuse that's popped... the next step would be, why did it pop?).

This damn thing is a puzzle dude lolol

[sswari]

So any of those values change if you have the car in R, N, D S or tip?

I would be looking for either loose or broken wires. Would a burnt fuse or fried relay cause issues at the Trans connector? And yes, the TCM is inside the Tans, I have one on my dresser waiting for a rebuild. I have a complete trans waiting for a rebuild or a buyer wanting to rebuild it. :)

[mkv]

I wouldn't be taking resistance readings on the plug of the 6HP19. There are warnings on every single guide (ZF, Audi or aftermarket) regarding how ESD can kill these TCM's, specifically when handling the mechatronic and TCM. When you take resistance readings it's injecting a voltage into that circuit.

Based upon your earlier fault codes, it looks like you're scanning with some sort of generic tool. One that only speaks to engine modules.
Do you have access to VCDS, or any other tool that can specifically talk to the Transmission, not just the engine like the generic tools do. Or if your scan tool can speak to other modules besides the engine, have you tried directly communicating with the TCM? It would be handy to have a VCDS autoscan readout here.

Search for Audi SSP385, which specifically covers the 09L transmission. If you look on page 18, you'll see that there's nothing you can really measure from outside the box. If it has power (check fuses) and it's not communicating with VCDS or another tool which can specifically read the TCM, it's probably dead or at least needs to be removed.

[jv_atc]

Dear mkv,

Thank you for your insight. For my understanding, you are saying there is no way to test/assess the proper function of the tcm? Two scan tools were used to populate the codes, first a snapon ethos plus, and then vcds. The vcds results were used to post results. The vcds was barrowed, yet I have located a genuine ross tech for sale in my area and have planned to pick it up Sat. I will then copy and paste it or send... results, which may not happen until Monday. I am pulling up the ssp385 now. The last time I checked, it had power, yet I will recheck tonight. If power is verified, my next step will be to drain and drop the at pan to access the tcm. Thank you for the ssp385 source, it looks very helpful.

[mkv]

Ok, looking at the codes again, I can see you have a combo of VCDS and the Snapon more generic P-codes.
The error about the ABS controller is just the engine ECU telling you that the ABS controller has a fault recorded, and I'm 100% sure the fault is that the ABS can't communicate with the TCU. All 3 of them are on the Powertrain CanBus and talk to each other all the time. Your vehicle has a a number of bus's in it, not just one big one.

If you look on that page 18, you'll see that there is a terminal 30 and a terminal 15 to the TCU. Terminal 30 on anything is permanent +12V, with term 15 being switched/ignition +15V. There's obviously also a ground. Then there's also the + and - for the powertrain canbus, as well as some other comms cables to other things like the shifter, etc.

With just 5 wires connected and working, namely terminal 30 and 15, ground and the powertrain canbus, you should be able to communicate with the TCU via VCDS. If those connections are fine, and there's power, then there's something wrong with the TCU.

I still believe that you have a connection issue, due to your recent interventions there. Let me look for a wiring diagram to help you out with some better fault finding.

[mkv]

Ok, so according to the factory wiring diagram, the pin numbers on the plug going to the TCU are as follows:

Pin 14 - Terminal 30, permanent +12V, 10A fused
Pin 9 - Terminal 15, switched +12V, 15A fused
Pin 13 and 16 - Terminal 31, ground
Pin 2 and 6 - Powertrain CAN bus
There's also a K-line (old style diagnostic line) on pin 3. Looks like it goes directly to the OBD port. You might be able to use your VCDS to communicate on the K-line. If you get comms, you have a wiring fault on the powertrain CAN bus connection to the TCU.

The powertrain can bus couples together in the sealed electronics box on the left of the plenum chamber/raintray. I think it's in the same box at the engine ECU, pretty easy to access. If you did the engine removal by removing the ECU from this box, which is how one is supposed to do it, then I guess there's a chance you disturbed the wiring in here.

Make sure you have power first on the TCU plug. both +12V's and a good ground.

[jv_atc]

mkv, I can't thank you enough! I have been lost for the past two weeks trying to figure this out, and 2 of my mechanic friends couldn't figure it out. I will share this information with one of my friends who will be able to interpret everything you said. Thank you so much. I will back working on the car after work today.

[jv_atc]

Update, 9.20

Checked and rechecked plugins, fuses, connections...

Per mkv, huge thanks for the important trans pin plug info...

Findings
Battery voltage = 11.44v

Pins 14 and 9 (ignition on) are powers, 13 and 16 are grounds

Pins 14 to 13 = 11.40v
Pins 14 to 16 = 11.39v
Pins 9 to 13 = 11.31v
Pins 9 to 16 = 11.30v

There is power and ground to the trans plug. The question, that will easily be tested, is now a higher voltage affects the function of the tcm with respect to the solenoids. I have read that the minimum voltage required is near 12.6v. The battery is new 4 months ago, been sitting.

I will charge the battery and if see if any change are realized. The most important conclusion is that both power and ground are present.

With respect to the tcm, and for future reference, are there known signs/symptoms of a unit that is on its way out? How common is a faulty tcm? Are there conditions that lead to its failure? Is the failure of the tcm simply a primary function of time? Should I expect any other damage to transmission components as a result of the failed tcm? Should I be considering a used transmission?

Any recommendations on companies that rebuild?

[sswari]

jv_atc, did you add or change the fluid in the trans? If so, what fluid did you use? and what is the software level of the TCM? just post the Transmission section of the VCDS scan. What I am looking for is the number after the USA in my case it is the 0040

This is just a long shot, but ....

Address 02: Auto Trans Labels: 09L-927-760.lbl
Part No SW: 4F1 910 156 Q HW: 09L 927 156 A
Component: AG6 09L 4,2 MPI USA 0040

[mkv]

jv_atc, did you add or change the fluid in the trans? If so, what fluid did you use? and what is the software level of the TCM? just post the Transmission section of the VCDS scan. What I am looking for is the number after the USA in my case it is the 0040

This is just a long shot, but ....

Address 02: Auto Trans Labels: 09L-927-760.lbl
Part No SW: 4F1 910 156 Q HW: 09L 927 156 A
Component: AG6 09L 4,2 MPI USA 0040

Hey Sswari,

I agree that we're going to start clutching at straws, but if the incorrect fluid was used we'd see a mechanical failure whilst still being able to access the TCU electronically. Although if the transmission does come back to life, it is a good idea to make sure that the correct lifeguard fluid was used, or at least one of the more reputable alternatives (like Ravenol 6HP fluid).

[mkv]

Update, 9.20

Checked and rechecked plugins, fuses, connections...

Per mkv, huge thanks for the important trans pin plug info...

Findings
Battery voltage = 11.44v

Pins 14 and 9 (ignition on) are powers, 13 and 16 are grounds

Pins 14 to 13 = 11.40v
Pins 14 to 16 = 11.39v
Pins 9 to 13 = 11.31v
Pins 9 to 16 = 11.30v

There is power and ground to the trans plug. The question, that will easily be tested, is now a higher voltage affects the function of the tcm with respect to the solenoids. I have read that the minimum voltage required is near 12.6v. The battery is new 4 months ago, been sitting.

I will charge the battery and if see if any change are realized. The most important conclusion is that both power and ground are present.

With respect to the tcm, and for future reference, are there known signs/symptoms of a unit that is on its way out? How common is a faulty tcm? Are there conditions that lead to its failure? Is the failure of the tcm simply a primary function of time? Should I expect any other damage to transmission components as a result of the failed tcm? Should I be considering a used transmission?

Any recommendations on companies that rebuild?

Ok, if you have power at the plug, then I believe there are only two other options here. 1) The comms connections are bad, or 2) the TCU is dead.

Have a good look at the CAN bus connections in that plenum chamber box. From the diagram the two wires look to be orange/brown and orange/black. The same wires on the same bus from the engine ECU and the ABS controller will be the same colour.

Why would the TCU be dead? It could be dead from ESD during handling when you were reinstalling the engine, maybe touching the pins of the unit. It could be dead due to a bad ground, like if the ground straps weren't 100% and the engine and TCU was drawing potential difference through other sources, like the circuits of the TCU. I'm brainstorming here, so this all isn't necessarily what happened. If it's really dead, it could have just been its time. Although that's very coincidental considering the timing and you say there was a noise. I don't see how a noise would kill the electronics, unless something broke off and rammed itself through the TCU..

I'm pretty sure the TCU will still be active much lower than 12.6V. During cranking the voltage can drop much lower than that. Still have a go with the charger though, but I doubt the success of this.

Ok to answer your questions: Signs of a failing TCU? I haven't really heard of one electronically dying. There are plenty of symptoms for a failing mechatronic unit (valve body), which the TCU drives. But apart from maybe on the Russian or Polish forums, I've never heard of one electronically dead, unless it was the result of a failed software flash.
I wouldn't expect damage to anything else as a result of the dead TCU. As per SSP 385, the transmission is completely disengaged, even with the transmission pump turning. The TCU can only drive the solenoids to pressurise or depressurise the clutch packs.

If your trans shifted fine before the work you did and subsequent breakdown, I wouldn't be looking for a new trans, rather a new mechatronic which you can salvage the TCU off. The TCU's aren't super readily available separately from the mechatronic units, but you can get them on eBay. Swapping this will come with it's own set of challenges, namely component protection which will have to be removed either by an Audi dealer, someone with Odis and access to the Audi network, or someone with and FVDI type tool.

I know that Sonnax in the US rebuilds mechatronics, but specifically asks that you take your TCU off before sending it to them. I have seen other companies which sell complete mechatronic and TCU units. Roughly $900 IIRC. In your case, if your trans was shifting fine and you just need a TCU, I would traul eBay for a used mechatronic with TCU on it, and just swap the TCU and get component protection removed and coding done.

This all assumes that whatever caused your TCU to fail is not still lurking, be it something electrical or something that's physically damaged the TCU or the wiring. There's still the possibility of an electrical fault in the engine bay.

[jv_atc]

Yes, the AT filter was changed, only after the problem exisisted, in an attempt to resolve the issue. And only after the car ran and drove. In other words, I completed the chain job, buttoned everything up and drove the car twice before I lost the AT, on the second drive, then tried the filter change, etc. Fluid? It's at my friends shop, maybe something like recline? I remember reading the label and it specifically listed the Audi spec standard. Software? I really don't know. I have plans to pick up the ross tech cable at 3:30 this sat, pst. My friend may not be at his shop, so I may have to wait until Monday to scan. I will post AT info as soon as I can. Would any of this explain the loss of AT?

[jv_atc]

mkv, I will examine the orange/brown and orange/black wires at the box for a quality connection, on the left side of the upper engine bay, opposite of the ecu. Is there any electrical testing I should be doing? I'll also recheck the grounds coming off of the ecu, yet I was sure they were well secured upon install. The esd is a more likely scenario. I suspect the noise was from the solenoids trying to engage. Perhaps the value body is defective, yet I suspect that would produce a different set of codes. Through this process, I did locate a private shop that has the odis and access to the audi network.

[jv_atc]

The 2 wires as well as, the plug and recpticle, as suggested by mkv, we're inspected at the engine box. Both the male and female components appeared as expected with no apparent damage. The last assessment will be to measure the ohms of the 2 wires, which I will do tomorrow. If the ohms are as expected, I will proceed with ordering a tcm.

As previously presented, would you also replace the solenoids?

Can a vcds be used to code the new tcm?

[jv_atc]

Update 9.23
Can bus connections/wires both showed similar resistance, I don't have a standard for them so I just checked using jumper. From memory, Pins 2 and 6 on the plug. I then searched for a remanufactured or used tcm unit and found only one matching my transmission code. I purchase it and looking forward to switching it out next weekend. I found several tcm's from the same engine size and transmission, yet with different transmission product codes. I was not able to very exact part numbers on the units with different codes.

I purchased a ross tech cable yesterday. After calling 4-5 businesses listed as partners or distributers on the sonnex website, I have not been able to find someone to rebuild or sell the kit. I did find a part number today for the kit. I also sent sonnex an email regarding a rebuild kit.

Does anyone know where directions for removing protection/security on the used tcm? Coding via ross tech looks straightforward.

[jv_atc]

Dear 95blkmax, I did the full chains, guides, tensioners, etc., job, everything was out of the car, transmission was then separated from engine, had the full harness out as well. I did pull the starter, after everything was reinstalled to inspect the plate and all looked good. Upon the outset, everything was fair game, but now I believe mkv helped get me on the right track... The TCM will be replaced and I will report findings. At this time, the transmission plug does have power and ground. The mystery is how the tcm, appears to have spontaneously failed. My concern is that it happens again. Thank you for your input.

[95blkmax]

Dear 95blkmax, I did the full chains, guides, tensioners, etc., job, everything was out of the car, transmission was then separated from engine, had the full harness out as well. I did pull the starter, after everything was reinstalled to inspect the plate and all looked good. Upon the outset, everything was fair game, but now I believe mkv helped get me on the right track... The TCM will be replaced and I will report findings. At this time, the transmission plug does have power and ground. The mystery is how the tcm, appears to have spontaneously failed. My concern is that it happens again. Thank you for your input.

Dear ATC, yes I gathered that from the thread (been following it lolol). I'm glad to hear and hopefully this works! Some had stated that the TCM is known to fail off of a simple ESD so it is quite the sensitive piece of equipment indeed! Like you gotta wear gloves to handle it type of thing.

Just as a tangent, when you were re-installing the transmission, at what point did you reconnect the battery? Was the battery disconnected at all? I know this is something that is frequently recommended to do but not often done. I know for a transmission removal I would have been one to not bother disconnecting the battery, lol. Just trying to think of reasonable ways one could inadvertently get an ESD to the TCM