Thaddeus

I suspect this workaround would not allow access to the airbag either.

Just out of curiosity: how does the 'hammer' get the data through the immobilzer barrier for Motronic and Airbag? There's no way Porsche would have done this if there own equipment couldn't traverse it. there's some added functionality there that would be good to understand before implementing any kind of workaround... maybe the hammer actuates the relay in the immobilizer when it's plugged in? maybe there's another such relay for the Alarm circuit?

PDriver

Yes, I think some software command will do it automatically with the bosch hammer to "switch" the relais in the immobilizer. The "workaround" do NOT deactivate the immobilizer. It is only for motronic diagnostics. I tried this with my '95 Cab with 55pin DME and with another '96 Cab with 88pin DME. On both cars motronic was unreachable until I applied the workaround. But on both cars I can reach ALL other control units, also the airbag! In both cars the airbag control units was directly connected to the other control units and the OBD-Connector.

@Bill
If you want to remove the immobilizer from your car, I agree with Loren, it is will be expensive. I think you have to change some control units, wiring harnesses and other things in your car. Or you have access to a 993 RS that do not need those parts anymore.

@993inNC
I think your airbag control unit has a connection problem. Get to a Porsche dealer and ask him to read out the airbag unit. If he fails to connect then there is a problem.

@all
Anyone tried to connect to the immobilizer control unit via Doug's software? The unit is also connected to the OBD connector. Or is this unit not diagnosable???

PDriver

cowtown

We're in agreement. I'm not commenting on bypassing the immobilizer.

I'll try to rephrase: contrary to one of the posts above, you CAN use Scantool and the raycm circuit board to read the K line IF you are willing to do PDriver's workaround. It's not correct to say that you can't read the K.

Hope this clarifies.
Colin

Lorenfb

"maybe the hammer actuates the relay in the immobilizer when it's plugged in? "

No, nor does the PST2. In both cases the remote must be activated first. So, why is this a
problem, i.e. activating the remote to access the DME, with the DIY scanner? Just activate
the remote first! The DME doesn't know/care "who's" trying to communicate, i.e. the Hammer,
the PST2, or the DIY scanner. Porsche designed the system that way so DME access is always
controlled via the immobilizer even when using scanners, e.g. PST2.

"The immobilizer unit is also connected to the OBD connector. Or is this unit not diagnosable???"

That's correct, i.e. the immobilizer has no diagnostics, only the alarm unit.
Both were combined into a single ECU on 996.

Thaddeus

So Loren, are you saying I don't need to jumper the lines to allow signal through, but merely activate the remote first? Are you sure? Because what several other people are telling me that the RC controlled alarm will not allow the scanner to function without jumpering the leads.

What do you recommend to 'activate the remote'? Because I have tried every possible permutation with zilch for results.

Lorenfb

"are you saying I don't need to jumper the lines to allow signal through"

I haven't tried using the DIY unit, but I always have to use the remote before using the PST2
and when working on cars at the Porsche dealers with their testers too. If your remote works
fine for allowing the car to start but not to allow the DIY to connect, then ???? Once the immobilizer
communicates ("handshakes") with the DME, i.e. the remote is depressed, it should switch
the relay so the DME K line connects to the diagnostic connector.

Is it really true that NO ONE with an immobilizer can access the DME without a workaround?

Thaddeus

That's what I've been told, in the case of folks with a radio controlled unit.

Felix

For what it's worth on my 97 ROW tt the OBD port is dead until the drive block is deactivated (with the remote).

Lorenfb

"For what it's worth on my 97 ROW tt the OBD port is dead until the drive block is deactivated (with the remote)."

Great! That corroborates what has been expressed before.

cowtown

Thanks Loren and phelix - great information.

Thaddeus

Well, now it sounds like what I was told on page 14 of this thread may be incorrect and there must therefore be something wrong with the interface board I built. I guess I'll start messing with it again.

Caveman

Sorry for the slight thread highjack but as some of you guys are obviously good with electronics would you have any good ideas how to address the backlight on my computer display (in the rev counter when fitted as an option) which is now only coming on intermittently? I'm assuming there is some sort of circuitry that turns this on and off that is getting a little tired?

Any ideas? Thanks for your thoughts.

Regards,

David

William Green

Have encountered a problem that I hope someone can sort out.

Checked that com1 is working by shorting out pins 2 & 3 and can see typing on the screen. Next plugged in serial connector and 2 LEDs light dimly, then started scantool and the 2 LEDs flash. Turned off scantool and plugged OBD connector in and started engine, the power LED glows dimly and then started scantool.

This is where it goes wrong!

The 2 LEDs that were flashing previously now do not light up and scantool cannot make a connection. Any ideas what I have done wrong?

PDriver

Update!

Until rereading the posts I did some different setups to try connection to the motronic. And suddenly scantool was connected to it without the workaround (switch installed to the immobilizer unit). So I retried to connect several times and here is my way to connect to the motronic in my '95 cab with remote and immobilizer:

Setup:
- Car closed and locked.
- Laptop inside and connected to OBD. Switches to:
- SW1/1 = DME/CCU/ABS/ALARM (not SRS)
- SW2/1 = DME (Motronic)
- Scantool4 not running

1. Press remote control to unlock the door.
2. Open door
3. Put the key into the ignition
4. Ignition on, but do not start the engine
5. Run scantool4.
6. Scantool4 tries to connect several times but fails.
7. Close scantool4
8. Run scantool4 again
9. Scantool4 tries to connect several times until connection is done. Scantool4 shows all data you need.
Note: If you switch off ignition you have to lock your car and do all this from beginning.

This work for me on my car. Can anyone of you with the same problems check this with your cars?

PDriver

Jeff96-993

When I hook up another OBD-2 reader on my 1996 it works great when the car is running.

Tried it once with the ignition on without deactivating the immobilizer and got nothing.

I'll give it a shot tomorrow with ignition on (not started) and the immobilizer deactivated.

If you start the car can you see the ECU with this homegrown scantool? Including the other systems like airbag and CCU?

Any advantages to not having the car running while doing the scan?