Well, I'm still trying to sort out the problem.

I'm beginning to think the 'load signal' error was a red herring. Since cleaning
up the knock sensor connector and clearing the old errors I now just get
"0 Unknown DTC: 0".

I did try swapping the throttle position sensor before I gave up on the 'load signal'
theory - made no difference.

An identical tiptronic ECU came up on eBay, so I tried that, just to confirm that it
wasn't the ECU. It responded in exactly the same way - immediately goes to 'limp'
mode and returns the same "0 Unknown DTC: 0".

I must be missing something obvious.

 

I asked Durametric about the 'unknown' error.
They have been very helpfull, but their conclusion was:

"Our engineers went over the log you sent. It shows the
requests for the fault codes. The Tiptronic unit provides
a confirmation, but doesn’t present any data. Our engineers
interpret this to mean there are no faults in your Tiptronic
system. We’ll make a better account for this in version 6
when support for the 964 is added."

Which means the Tip is going straight into 'limp' without any
error code... very odd.

I wonder if the Tip unit is waiting for some missing input
which is required before it even boots-up? I can't think what
this would be, the total list of error codes it can produce is
pretty comprehensive.

 

I eventually conceded defeat and took the car to a highly regarded,
independent, Porsche garage.

They've tried a number of thing, but were pretty foxed.

However, I've just spoken to them and they think it's caused by the Tiptronic
ECU not receiving an injector pulse signal from the DME ECU. (I didn't even
know that this signal was required... I can't see the input pin mentioned on
the list of Tiptronic ECU connection pins.)

They claim that by bridging the wire straight to the Tiptronic ECU, it behaves
correctly.

They had tried a DME ECU from another car but get the same fault.

So, two questions:

1) Can anyone give any more information on how this signal is generated?
I assume it's not processed in any way by the DME ECU before going to the
Tip ECU?

2) Is the DME ECU the same in both tip and manual cars?


Rich

 

Can't answer those questions Richie, but at least there is light in that very long tunnel!!

 

from the 993 info

The DME control unit is fitted to the
transmission control unit. It supplies the
following input signals to the transmission
control system:
Rpm signal
Fuel consumption signal
Throttle potentiometer signal.
If one of those signals is faulty, the "emergency
mode" is selected.
Upon a command sent by the transmission
control unit, it can also retard the ignition angle
in the moment of shifting.

Fault code 22

Tiptronic warning lamp comes on, transmission is in emergency
mode
Possible faults: Open circuit, short to ground, short to positive, loose
contact
1) Signal check
Check signal with Tester 9288 (injection time) with engine running
Check signal with oscilloscope at transmission control unit connector
pin 21.

If signal o.k.: Transmission control unit faulty
Signal shape: ti signal
2) Open circuit, short to ground, short to positive
Check wiring according to wiring diagram. Check transmission control
unit connector pin 21 to DME connector pin 17 for continuity,
short to ground and short to positive (Ground at transmission control
unit connector = pin 7, positive at transmission control unit connector
= pin 1)
Connections o.k.: DME control unit faulty

 

I believe DME's are the same between TIP's and manual cars, however, the wire loom has two plugs for jumpers. According to Adrain's book, jumpers are installed on the 3pin and 2 pin connectors on TIP's. Though it's for emission reasons as referenced in the post>

https://rennlist.com/forums/964-foru...-question.html

From what pin on the DME to what pin on the TIP ECU are they bridging?

 

Just a quick update.

I picked the car up from GT One - they managed to find a solution.

When they connected their diagnostic machine to the car they noticed that one
of the parameters was missing (the injector pulse), but the engine ran fine.

After swapping both Tip and DME ECUs, with no effect, they decided to create
a jumper between the green and white wire (goes to dash computer for fuel
consumption calculation and to the tip ECU) and the brown and black wire
(pulse from injector to DME).

I had assumed that the DME ECU would process the signal in some way before
passing it back out to the Tip ECU, but obviously not.

This would also make sense as I occasionally got a "22 - load signal" error
before it went solidly into 'limp' mode.

It has now run perfectly for several weeks including one day were I drove
for six hours. So I'm hoping that's it!

Thanks very much for all the helpful post, especially mojorizing who PM'ed
me to offered lots of help.

Well done GT One ! They were very helpful and kept me
updated as they worked through the problem. I highly recommend them.

 

Glad you were able to get her back on the road Richie.
I apologize for the thread jack, but is there a method to swap a Tip to manual transmission? I’m pretty sure it has been discussed but I honestly didn’t find anything during a search.

 

Hi Shellback

No need to appologise about the 'thread jack'... I hi-jacked it off Jason(BLK964)
ages ago!

There's a discussion about the Tip to manual conversion here.

Rich