Porsche964FP

mojorizing

Check the connectors on top of the engine. There's one, could be the TPS, that is orientated in such a way that rain water can fill the boot of the connector. It sits right below the spoiler grill. You'll see water inside the lower half of the connector when you pull it apart. I'm not at my car, so I can't be to specific on location.

RichieRoo

Yeah, thanks Mojo. I did try that. Unplugged the connectors, all looked fine inside,
gave them a waggle. No change.

Another trip to work in third gear.

Do you know if the warning light will go out immediately when the problem is correct,
or only when you restart? i.e. if I waggle stuff whilst the light is on, will it go off,
or once tripped it stays tripped?

kenloen

when I was having electrical issues, if the car had gone in limp mode the engine had to be restarted to reset.

not confined to just Tip faults though - but my resolution was re-soldering all the connections int he clock!! was damp cold days when there is condensation inside the car I was having most problems with. If you do decide to strip and re-solder the clock joints, beware - there are 3 pins connect the inner and outer PCB, you need to solder mop these completely before prying apart, if you don't there is a chance of damaging the pcb tracks. took me around 1 hour to remove re-solder and put back.

good luck!

RichieRoo

Ok... Just checked all the obvious connections in the engine bay. All clean and dry.

Took the clock out, disassembled it, carefully re-soldered everything and
reassembled.

Took the seat out and whipped out the Tiptronic ECU, opened it up and gently warmed
it up with a fan heated then quickly tried it back in before it got really cold again.

Nothing worked. The Tip warning light comes on as soon as you turn the key to the
second position and stays on

Just put it up on ramps to take a look underneath.

Any more ideas? I'm getting really stumped now.

RichieRoo

Does anyone know how I can check the 'Load signal' input at the Tiptronic
control unit plug?



Load signal is pin 21, but I've no idea what the expected values are (at rest,
engine off). Am I looking for a given resistance across two pins or a voltage
output?

In fact, if anyone knows any values for any of the inputs which are likely to
cause 'limp' mode at start up, please let me know.

Thanks

Rich

mojorizing

Rich,

Have you been able to pull the error code from the TIP? Do you have a scantool?

jimq

scantool doesnt read the TIP

RichieRoo

Yeah got an error code '22- Load Signal' (I have the Durametric unit and
it reads Tip codes).

But that's not really helping me because the only reference I can find to
trace the fault is Adrian's "Technical Data" manual, which states:

Pin 21
Connection ECM (T32), speed sender (T22) with on-board computer
Function Load signal ITD

I can't determine - what sensor generates the signal, whether it's a signal
sent out by the ECM or what the signals type is (e.g. a given resistance /
voltage).

Initially I assumed the 'load signal' was generated by the TPS... but Adrian's
book says that:
'Throttle valve potentiometer' voltage signal goes to pin 8
'Throttle valve potentiometer (T4)' goes to pin 27
'Throttle valve potentiometer (T5)' goes to pin 44



Whichever it is, it fails before the engine is even started. Any ideas?

mojorizing

I believe the load signal is generated in the ECU by the fact that the load signal can only be read from the ECU by the hammer and not from the TIP......according to my notes. Actually, the load signal displayed on the hammer from the ECU is a percentage IIRC. Does the Durametric display the load signal when connected to the ECU?

I'll have to look at the schematic to confirm what Adrain's book says. I'm on the mainland right now but when I get home I'm willing to give you any readings from my TIP or ECU.

@jimq
The scantool can connect with the TIP, but you need to add some statements to the .cfg file to make it work. I post that soon.

RichieRoo

Thanks. Really appreciate your help on this one.

The Durametric unit give live readings from the main ECU but not the Tip controller
(only error codes from Tip). I'll check the Main ECU live output to see if there is a
'load signal' parameter tomorrow.

mojorizing

'Throttle valve potentiometer' voltage signal goes to pin 8
'Throttle valve potentiometer (T4)' goes to pin 27
'Throttle valve potentiometer (T5)' goes to pin 44


Pin 8 on the TIP is the analog output from the pot on the throttle valve
Pin 27 is the +5vdc reference voltage on the high side of the pot
Pin 44 is the ground reference voltage on the ground side of the pot

FYI, there is a WOT switch in the throttle valve along with this pot. Anyway, I believe this pot. is the sensor that generates the Load signal out of pin21 going to ecm-32 and speed sender-22. I'm not sure if that's an analog signal or PWM or ?

RichieRoo

OK. If the TPS values are used to calculate load, then I'll order a new one, just so I can
rule that out. Then I'll work from there back to the ECU, then I'll try to work out what I'm
looking for at pin 21 on the Tip ECU to check that's receiving whatever it should.

Thanks for you help Mojo. I'll keep you posted.

If anyone suddenly thinks of another possible cause, or something to check, let me know.

mojorizing

You can wait a few days and I'll measure the wiper resistance on my throttle pot to compare with yours...

RichieRoo

Bit more info:

1) After about 45min of driving in 'limp' mode (in freezing conditions):
The tip ECU resets, drops the car into neutral then works correctly for
a few seconds before returning to 'limp' mode. It has done this
numerous times now, always around the 45min mark.

2) Hooked up the Durametric and reset the Tip ECU error log (clearing the
'22 - Load signal' error). As the Tip ECU reboots, it must do fundamental
checks (I guess to ensure sensors are present). It fails, as per usual,
but the Durametric reports a new '0 Unknown DTC:0' error.

3) The 'Load signal' can be read from the main ECU (see graph, two blips
are squeezes on throttle whilst stationary).



I'm thinking we can rule out anything to do with engine variables as the error
occurs before it's even started. How can I find out what the Tip ECU requires
to boot up successfully?