Tiptronic Limp mode

[996ttalot]

Hi,

We replaced the existing tip box last week. The previous tip box was not giving any errors either in DME or TCU. The previous box had a minor leak on the input shaft seal/oil pump and is currently being fixed.
However since we had a spare, we stuck that in, but as soon as we did this, and turned the ignition, we got a p0702 error in both dme and tcu. Effectively it is in limp mode.
The code points to electrical issue, mainly down the route of fault TCU. But it was working fine before. Since the engine was out, the battery was disconnected for a couple of weeks. The battery is fine.
When you clear the code, it just comes straight back.

If it is the TCU, then does anyone know anyway other than through OPC to recode?

The other issue is that if I need a new TCU, then I also need to send that over to Germany to get the tq limits increased. The tiptronic box is uprated by a company called MKB to 1300nm tq.

It just seems strange that swopping the gearbox over, we now get this message. The new gearbox was effectively brand new and had previously only 500 miles on it.

It just seems like the TCU is not taking to the DME.

 

[Richard_Hamilton]

Ken!

Sounds strange. P0702 indeed relates to control unit failure from one of the following causes:
56 Control module faulty, coding fault (EEPROM: variant impermissible)
57 Control module faulty (clock)
58 Control module faulty (test internal watchdog)
59 Control module faulty (test external watchdog)
62 Control module faulty (RAM)
63 Control module faulty (ROM)
64 Control module faulty (EEPROM critical for normal function)

It might be worth double-checking the main connectors, or you could try recoding and adapting the module. Anyone with a PST2 or PIWIS should be able to code the Tiptronic control module. The Porsche IPAS codes are not required. This is the procedure from the workshop manual:

Coding the Tiptronic control module

Note
The adaptation values must be reset using the Porsche System Tester when the transmission is renewed/replaced.
If a new control module is installed, the control module must adapt first. Poor shifting quality can be expected therefore in the adaptation phase.
After the test drive, let the engine run for 10 minutes at idle speed. This ensures that all adaptation values are stored in the control module.
The instructions of the Porsche System Tester have highest priority.
The procedure listed has been structured generally, changes or additions can be made. The basis of this is the Tester Software 13.1.

1. Connect the Porsche System Tester to the vehicle and start the System Tester. Switch ignition on.
2. Select vehicle type using the cursor keys.
3. Using the >> key, move from the vehicle type to the list of control modules.
4. Select Tiptronic with the cursor keys and press the >> key.
5. Select "Coding" with the cursor keys and press the >> key.
6. Select vehicle version and code with the F8 key.
---RoW/ Japan P 80
---Taiwan/ Korea P 83 / P 84
7. Tester confirmed: Coding has been modified .
8. Perform test drive and check fault memory with the System Tester.

Resetting adaptation values:
Proceed as described under point 1 - 4.
Select menu item Reset adaptation values proceed with >> .
9. Confirm with F7 for Yes , F8 for No and proceed with >> .
10. Follow the instructions of the tester.

If you are anywhere near me I would be happy to have a go for you, but I'm a bit tied up this weekend picking up my new car.

Hope this helps.

 

[996ttalot]

Richard,

Thanks firstly for your reply.

I think we will check the connections first. Given the input shaft seal had gone, there was an ATF leak, it maybe that the oil has got into something else that it shouldn't have.

The wired thing is this
- original had a tip box in the car
- brought another gearbox and sent that to Germany along with the TCU. The TCU was programmed to allow higher tq limits. The gearbox was upgraded with increased clutch packs, housing, control value unit etc to handle the power I wanted.
- the upgraded gearbox and TCU was then put back in the car
- there was no issues, adaption values where reset anyway.
- ran the car and hit an issue with the Wheelset in the gearbox (rear diff) was on it's last legs.
- You just cannot buy a Wheelset to save your life, so I sent the original gearbox over to Germany, who by this time, had the upgraded box back.
- they created a new gearbox from both boxes
- TCU had remained in the car all this time
- new gearbox was then installed and no issues with pcodes.
- then i get this input shaft leak, which is a common issue in MB boxes.
- in the meantime, because of the inability to get a Wheelset, another gearbox became available from the US, I brought this and had it shipped directly to Germany, who then upgraded.
- was about to send back the gearbox with the input shaft leak when the box from the US was completed, and shipped from Germany to me.
- so i thought i would stick that in instead of being off the road - also whilst the other gearbox was doing well other than this leak, it has a lot more mileage on the main components where as the one from the US had only 500 miles on it, so I knew that the gears and Wheelset would be better. It didn't matter about the clutch packs, value body etc, because they are all replaced during the upgrade.

Then as soon as switch the ignition on, the message was displayed.

So the TCU was working fine before, and hadn't needed recoding at any time. Although I suppose the fact that the TCU and Gearbox went over to Germany the first time, it was probably matched.

I suppose another issue could be that since it has been taken out many times, it could be that some of the wiring on the harness might have an issue. I cannot imagine that it would be designed to be removed as much.

I am waiting for the guys in Germany to come back early next week with some suggestions. I have not recoded either the DME or the TCU since the box was taken out.

It could be an issue with broken wire I suppose.

Ken

 

[Richard_Hamilton]

I would check the obvious, like connectors, and then see what MKB have to say. Re-setting adaption values should be OK, but re-coding might upset their program, which isn't worth the risk.

 

[996ttalot]

ORIGINAL: Richard Hamilton

I would check the obvious, like connectors, and then see what MKB have to say. Re-setting adaption values should be OK, but re-coding might upset their program, which isn't worth the risk.

Yep I tend to agree Richard. I'll post up next week when I make some progress. Ken

 

[996ttalot]

Update.

So the result of the p0702 code is a new TCU.

New one was installed and then sent to MKB for tq limit increase and everything is working fine. I also sent my old TCU to MKB who were able to read it fine, and they reset all parameters back to Porsche settings. However when I put the old one by in my car, turned the ignition on, immediately went to p0702 error. So clearly something is wrong with the TCU.

Have to say I am surprised that a TCU could just become corrupt like that. Would really like to find someone who could explore the old TCU to see what is actually wrong with it - anyone know a company or someone?

 

[Richard_Hamilton]

I don't know anyone who specifically does Porsche ECU's, but there are plenty of repairers out there. My brother used a company called BBA Reman for an engine ECU on his son's Golf, and had a good result. Might be worth a call. http://www.bba-reman.com