Re: What is the model year of the car?

I have not driven my car for a few months. I have started it and moved it around though. The car sits on a battery tender. I went out today to start it and it seems that the immobilizer won't let the car start. I tried both regular and valet keys. I also checked the fuse on the immobilizer itself and the fuse panel fuse. The car locks and un locks and the interior lights do what they are supposed to do. Any ideas? Thank you. - Jason

Jaay:
I would first replace the electric portion of the ignition switch.
Sounds as though the CLU is energized but not the DME.
Also check the connector an wiring into the DME.
Good luck chasing this gremlin.
Happy Boxstering
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

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Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

Pedro, Does the ecu have more than one power source? Main power in but then maybe a switch by relay source that comes from the ignition or immobilizer?

If the dash lights all come like normal and the interior lights ditto but when you turn the key the starter makes no attempt -- doesn't even make a clicking noise -- to spin the engine that can be a clutch interlock switch, provided of course your car is equipped with a manual transmission. If it is a Tip car the gear selector may not be recognized as being in the right place (Park or Neutral.)

For a manual fully depress then release the clutch a couple of times in rapid succession then try again. Be sure you are pushing the pedal all the way down, that there is nothing -- the floor mat for instance -- interferring with the pedal.

For a Tip move the lever around than back into Park or Neutral.

While you are doing one fo the above be sure the igntion is off.

If the dash lights don't all come on if the interior lights don't all come on this can be a bad ignition switch. It can be a bad ignition switch if they do all come on, too. Briefly, when the key is turned an RF signal is broadcast from an antenna located behind the key surround in the dash. This RF signal is received by the RFID pill inside the key head. This energizes this RFID pill which in turn then transmits its ID. The antenna picks up this transmission and it is carried to the DME (or the security module) where it is decoded into a digital number. If this number exists in a table of numbers the starter is powered up and the engine starting process is begun. If the number is not recognized, or the RFID transmission is not received, of course there is nothing but crickets from the car. In some cases with the Porsche diagnostics computer a tech can query for an error code and something to the effect bad ID or no ID received can be retrieved which to a tech maybe proves helpful.

Try moving the key around as you turn the switch from off to on. If you are able to stumble upon a position that the dash lights look normal, or at least the engine cranks/runs, then the switch is pretty much bad.

I have to mention that with a car not driven a while -- the occasional starting the engine and moving the car doesn't count -- the car could have been infested with mice. They can wreck havoc on the electrical wiring. You have to carefully check out the car, under the seats, the passenger seat especially for that is where the security module is, and on top of the engine -- you'll have to expose the engine of course -- and if you can look on to of the plastic panels under the body for mice sign.

There are a couple of fused circuits involved. At least one for the DME and one for the security module. I'm not sure the fuse chart on the inside of the fuse box lid is that comprehensive. You might have to ask for a more comprehensive one at the dealer, maybe the parts department can print one out for you? (The Boxster Bentley book as some charts but nothing newer than 2001 in my edition.)

Car is a manual. All dash lights are on. I can not stress enough that the dme is not connecting to the obd2 port. There is power there but will not connect. The alarm stuff if under the drivers seat and has power and fuse is good. Not corroded or wet. The car lives in a garage. Ordered a new ignition switch and will go from there. Thank you for the indepth RF knowledge. I feel like it is something to to do with the CLU.

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Jaay
Car is a manual. All dash lights are on. I can not stress enough that the dme is not connecting to the obd2 port. There is power there but will not connect. The alarm stuff if under the drivers seat and has power and fuse is good. Not corroded or wet. The car lives in a garage. Ordered a new ignition switch and will go from there. Thank you for the indepth RF knowledge. I feel like it is something to to do with the CLU.

If the DME is powered it should "connect" to (service) the OBD2 port. If you are savvy with a volt/ohm meter you can check for proper power and ground. Power (battery power) is pin #16 and chassis ground is pin #4 and signal ground is pin #5. Could be only one "ground" pin is used, I forget which one. Wait a minute: I just checked. The OBD2 data loggers I worked on only have one ground pin, pin #5, populated.

Looking at the connector the top row the pin count starts counting at 1 in the upper left hand corner. The count stops at 8 and then one starts counting at the 1st pin of the 2nd/lower row. Pin #9 is the lower left hand corner and counts from 9 to 16.

Here is the link to the Wikipedia article on OBD2 and it shows the female connector pin locations and definitions:

[en.wikipedia.org]

The communication protocol is probably ISO-9141-2 and this can take some time -- seconds -- of back and forth before the OBD2 tool will establish connection/communication with the DME. I can vaguely recall and count the number of vehicles with bad OBD2 ports/connections on the thumbs of both hands. One the owner damaged -- I seem to recall he said he kicked it with his foot somehow -- and another was a car with a leaking windshield which allowed water to get in the connector and its wiring connections.

If the problem is with the CLU (security module) you might need a Durametric or even a tech with access to a Porsche diagnostic computer to query the unit for any error codes and from these then possibly get a clue as to what is the problem. Besides either replacing or having the unit possibly "repaired" it is not a field serviceable item so there's not much you can do if this is acting up. The CLU/security module relies upon a number of sensors though and if a sensor is bad it can possibly interfere with the starting process and in this case one can field service (replace) the sensor.

What model year car do you have? If you have a 2001 or older the Bentley manual lists all the fuse assignments and relay assignments and locations. If you have a later model car maybe a later edition of the Bentley manual covers these or you will have to perhaps consult the owners manual or get this info from your local Porsche dealer?

'course, it is up to you. You can throw a new ignition switch at the symptom. The electrical portion at the back end of the assembly is not that expensive -- used to be Audi sold one that was compatible with the one supplied by Porsche and considerably less expensive (if Porsche even sells this separately now which I don't think it does) -- but it takes a bit of work to remove the old unit and install the new unit. One has to be/should be careful back there as the wiring is getting old and possibly brittle.

Also just thought... DME Relay maybe? Can anyone point me to the exact location for the DME's relay. Thank you. I feel it is work a look.

So update... Nothing to report really. I jumped the starter relay to see if the all the starter and motor turns as normal. ---- It does. Cranks and sounds great just as always. There is power to the ecu. It still won't mount up to an OBD2 computer. Driving me nuts. I don't want to have to bring the car to a dealer as I am trying to sell it. Throwing dealer money at it would be nuts. Is it possible for the ecu to lose it's programming? I read a situation where a guy with many similar symptoms had to eventually get his ecu re programmed. Updates to come (hopefully) Any other thoughts from you all are greatly appreciated. - Jason

For the 2000 MY there are a number of fuses that have some connection (no pun) to the DME and OBD2 port and of course other critical electrical circuits.


B1: Instruments, OBD2 (diagnosis) plug, Tiptronic, traction control switch.
B8: Alarm Control Module, DME Control Module, Tiptronic Control Module.
C1: DME: main relay.
C2: Fuel injection, ignition, O2 sensors.
C4: Fuel pump relay.

As for the ECU losing its programming. The program resides in FLASH memory and it takes some effort to change this memory. (My latest project at work had me writing a FLASH memory read/write/erase driver for an embedded system.) Barring a failure of a part of the FLASH about all I can think of is a FLASH write function was passed an invalid argument and erased/rewrote the wrong place in the FLASH memory region and this has resulted in compromising the program image/constants stored in FLASH memory. This could arise from a "bug" in the program.

The only way to know if this happened would to take the car to a dealer (or a very well equipped and knowledgeable indy shop?). With a Porsche diagnostics computer the tech would check the integrity of the image -- or just reflash it -- to remove this possibility of a bad image/corrupt image.

The car is a 99 with the stock ecu that has been reflashed 7 years ago to a 996 3.4 program. I never had a problem. I am just trying to avoid the dealer. They hate my car. lol

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Jaay
The car is a 99 with the stock ecu that has been reflashed 7 years ago to a 996 3.4 program. I never had a problem. I am just trying to avoid the dealer. They hate my car. lol

Well, if you suspect the DME/ECU image is bad, has suffered some kind of a drop out or corruption of its contents for whatever reason, you are I think going to have to visit a dealer, or possibly an indy that is set up with the right tools, that can verify the integrity of the image or just reflash it -- with the appropriate 996 3.4 image. Pretty much like was done 7 years ago. Where was that done? Can you return the car there?

'course, you have to exhaust all other possible explanations for the behavior to make sure your trip to the dealer -- if it comes to that -- is not in vain.

It was programmed by a porsche guy I knew from another forum. Todd was his name. I am going to see if a buddy of mine can take home his piwis from work.

Grabbing my old trailer that one of my best buds still owns and dragging the car to porsche. going to throw it on a PIWIS and also have new fobs and CLU on order for monday. I hope this is it. I'll def. update soon.

Went to the dealer yesterday and plugged in their computer. Still nothing. We all seem to think it is the dme. I am going to be borrowing a friends dme and clu and see if thats it. I will update soon.

UPDATE! I was away for a few weeks. I went through the wiring and found....... Underneath the trunk/hood latch assembly where the harness comes through to the CLU----- 2 mice chewed wires in half. With a quick strip and twist of them together the car fired and was perfect once again. Lesson learned, kill all mice! Now time to make it pretty with solder and heat shrink. Thanks for everyones input.

Glad to know you found it.
Remember when we spoke that I mentioned that mice like those wires?
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

---

Racecar spelled backwards is Racecar

"Racing is life. Anything before or after is just waiting" ... Steve McQueen as Michael Delaney in "LeMans"

"If you wait, all that happens is that you get older"... Mario Andretti

"Being second is to be the first of the ones who lose" ... Ayrton Senna

They loved about an inch worth of each wire. Crazy little critters. I hope it hurt on the way out!