Help: Driveblock malfunction ??

[911cedric]

Hello there,

I need all your help before I go crackers

my 993 do not start anymore. Before that, the car started erraticaly, sometimes yes, sometimes no.

The car doesn't crank, the DME relay doesn't click, only relays kl 15 and kl X work when i turn the key( i don't know what is their function). As the DME relay doesn't work, the fuel pump doesn't start. However, when i bypass the relay, the pump works correctly, but the car doesn't crank.

The dashboard lights up normally on key positions 1 and 2. Battery is good of course.

The remote key / alarm seems to work correctly.

First thing i did was to plug my PST2 in the diagnostic socket to pull out some eventual error codes.

By the way, I read somewhere that if the driveblock system works, the car cannot be scanned; do you know if it's true?

However, i went through the car with the PST2 but the diagnostic of the DME end Alarm units / immobiliser came free of any fault code.

After that, i changed the DME relay; didn't changed anything

I tested the pins from the DME relay socket, and i found out that no signal shows up when the key is turn on position 2(ignition).

I took appart the ignition switch and tested it; the unit worked fine. I had for that to dismantle half the car (you need to take appart the knee protection trim ; what a pita).

I put off the seats and had a look on the alarm unit on the passenger side and the driveblock on the driver side, i checked the connections and interior circuits without any clue of damage.

I'm now waiting for next week to be able to switch the driveblock and alarm units from another 993 to see if it would come from there.

I'm for now really thinking about a Driveblock / alarm unit failure.

If this doesn't change anything, i wouldn't know what to do next...

What do you think?

Any idea or suggestion is welcome!

[911cedric]

the car is a 1996 carrera convertible with manual transmission.
The car has the OBD2 diagnostic system.

the steering wheel is on the left(it's an american model)

993 618 159 02 anti drive off (driveblock system) unit 315mhz
928 618 260 03 alarm system

Everything is stock; no aftermarket alarm; the DME is original

the airbag system is present and all stock; no error code

i only have one remote key; hope this is not the problem

when the ignition is switched on, the car doesn't crank at all, and the dme relay doesn't work; exactly like when the driveblock system works after 1 min off with doors left open.
i was before able to start the car half the time; but now it seems to have totally die.

Regarding the emergency log in code for the drive block system, i'm not familiar with this. Is this a code you can enter via the PST2?

[ischmitz]

Without being absolutely certain the car should crank no matter what the alarm unit/driveblock situation is. Driveblock prevents it from running by disabling the DME. I believe you are correct in that once the alarm unit is triggered the K-line from the DME is not routed all the way to the PST-2 and you would only be able to talk to the Alarm unit. Porsche calls the K-line from the DME W-line. And it goes through the alarm module.

I think your error is something a lot simpler. Starter relay or starter motor come to mind. Get yourself on of these cheap remote starters from Sears, hook it up to the starter, turn the ingition to ON, take it out of gear !!!, and press the button. If it doesn't crank replace your starter. If it cranks I bet it will run.

Ingo

[911cedric]

Hey ingo,
thanks a lot for the suggestion

the thing is however, that the driveblock system disables the DME terminal 15 (port 56 on the DME) and the starter.
I'm sure about that because many 993s came through my garage.

My DME is the Motronic 5.2

If the driveblock works, only the dashboard should be lightened up, and only the alarm system is available through the PST2.

There is one error code for the driveblock system that can be generated by the dme in case of malfunction. I know it because it showed up when i unplugged the anti drive of unit from the DME. In normal conditions, the DME doesn't generate any fault code.

There is no starter relay on manual 993s; only on 993s equiped with automatic transmission.

There is only this DME relay that i already replaced.

I just wonder what are those two relays:
- Terminal X (R11)
- Terminal 15 E (R33)
they seem to click when i turn the key in ignition position; but not the DME relay

[ischmitz]

I am talking about the relay that is mounted to the starter and not a relay in the central fuse box. You need to get under the car. This relay switches power to the starter motor and engages the starter motor sprocket to the ring gear on the flywheel. It is a round cannister about 6 centimeters long and 3 centimeters in diameter. I has two M10 screw terminals (+12V battery and starter motor) and a spade connector where a yellow wire comes in. The once you short the yellow wire to the permanent positive lead the starter will crank the engine. Be careful, when you short the permanent positive to GND you WILL fry the wiring between the battery and the starter. There is no fuse and you'll have several 100 Amps wreck havock.

Relay X and Relay 15 come on when the ignition key is switched to ACC and to ON. They control loads such as windows, intrument lights, cigarette ligher, etc. This has nothing to do with your problem.

[ischmitz]

see here - it's also called starter solenoid http://www.thisoldtractor.com/gtbender/print/print_loopframe_electrical_starter_and_solenoid_re pair_-bosch-.htm

[911cedric]

thanks a lot for your advices.

i would definitely think about the starter solenoid if the DME relay would work when i turn the key in the ignition switch. Normally, when you just turn the key on position 1 (contact) with cold motor, the fuel pump starts working 30 seconds to initiate the injectors.
This doesn't happen

do you think a starter problem could lead to such a problem?

i even checked the DME relay connections with a friend, and we found out that no signal shows up when i turn the key in ignition position.
It probably means that the DME unit doesn't generate the term 15 signal.

That's why i was thinking about switching with another car, the DME, the driveblock unit, and the alarm unit to see wich one is defective.

The problem is that i will only have another 993 next week and this one will have the motronic 2.1 as it's a 1995.

i will have a driveblock unit 993 618 159 01 working at 433mhz instead of the 993 618 159 02 working at 315mhz; i don't know if this will work.

do you know if a driveblock or alarm unit replacement requires a DME reprogramming? what i mean is that maybe, each immobiliser generates a single signal that needs dme reprogamming to be read? i hope not.

I know for sure that it exists two different DME units for vehicles with ou without driveblock but i have no idea if they have an individual program for each driveblock unit.


do you have your idea about that?

[ischmitz]

Don't know about the fuel pump logic on a 993. On a 964 the pump will NOT come on unless flywheel motion is detected. And I am reasonably confident an OBD-1 993 is the same. There isn't really a reason to prime the system like you describe because there is a check valve in the fuel supply system.

I think you have an issue with your starter soleniod.

And yes, the drive block requires special codes from the factory to be re-programmed. You can not just switch one of the components from another car into yours. I won't work. The DME and the alarm system talk to each other and check whether they "belong" to each other for lack of better words.

ingo

[911cedric]

Hey good news my car finally works!!

I have to tell you the most absurd story ever happen with this car.

I was working again on this car this afternoon; thinking about the most complex problems, when i just got the idea of checking the starter relay port located in the main fuse box. I'm almost sur that this relay never existed untill now; and the the car still drived!
i just put the foglights relay in the starter relay port...the relay immediately switched and the car started when i turned the ignition switch.

I really don't know what happened.

I couldn't have moved a relay to a wrong place because they are all at their place;
i checked each of them several times, and they all have their function!

i have to reassemble half the car; because i took so many things appart.

anyway, i checked on the PET and it appears (my mistake) that the relay R61
is available for cars coming with the folling options:

259 tiptronic transmission
480 six speed gear box
530 remote control (i guess)

the problem still is, how come that the car started before half the time?
I have to check in the coming days if the problem remains.