No signal from OBD Computer system

I have a 99 C2 996 which is coming up for it's Annual inspection. I bought the car in April of last year. In October of last year I got a form from the test station saying:- ----------------------------------------------------------------------------------------------- The overal test results: PASSED. Emissions Control System Visual/Functional Inspection: PASS. OBD Emissions Inspection: N/A Sticker:IM12342304 TIN:758945637 Based on the information gathered during an attempt to perform an On BOard Diagnostic test. NO Signal was available from the On Board Diagnostic Computer system. This vehicle should produce a signal from the On Board Diagnostic Computer system. This vehicle needs to have the above problem corrected prior to next years emissions inspection. ---------------------------------------------------------------------------------------------- My questions to you guys are. Where is this OBD computer sytem located? Would anyone know the cost of replacement? What does the on board computer system diagnose? In other words 'what does it do? The car has been running great ever since I got it and still is over the past 17,000 miles.

The OBD (OnBoard Diagnostic) port should be located under the dash, left of the steering wheel near the fuse box. Plug in the code reader in the port to read fault codes that the ECU/computer records. P.S. Had a similar experience on my daughter's truck (i.e. code reader could not connect to the ECU) and the cause was a blown fuse.

Kromdom I hope thats all it is. A blown fuse but where would I find the fuse on a 996 to this socket/system? Nothing mentioned about a fuse controlling this unit where the computer diagnostic computer plugs into in the fuse box by my left foot. I have a small leaflet in several languages as to which fuse controls all differant circuits and nothing mentioned on it about the onboard computer. I now know where the turquoise plug is situated under the dash by my left knee. Where is the fuse to this socket. All the fuses in the fuse box are in good shape as i have checked them several times when trying to solve a covertible top movement problem. Which BTW I solved a month ago. So all the fuses in there are good. UNLESS one of them is missing to this dead system. Somethng else along the same vein is bothering me. I felt behind the actual colored socket where the computer plugs into and cannot feel any wires going into it. Can you feel wires going into the back of the socket on your car or do they come out of the side and dissappear under the dash board somewhere? Anyone with a 99 model please? I just found a fuse missing on the bottom bank of fuses for 'Info System' in the main fuse bank down by my left knee.It takes a 7.5fuse. I couldnt manage to buy that size so I put in a 5amp. No blow so i upped it to 10amp. We shall see in the morning when I take the car for its annual inspection if that did the trick.

Instead of feeling what is behind the OBD socket, why not get under it, take some panels off and visually check what exactly you do or don't have? Also, look inside the socket and see if any of the pins are bent, missing of partially pushed out. You are going to have to do some work to figure this out.

This is a strange one! What you are referring to is the DME/ECU OBD port located under the left side of the dashboard. That is where you will get the OBDII readings from the ECU. The actual DME/ECU is protected by a 15 amp fuse at B8 in the fuse block. The DME/ECU is located under the seat. However, that fuse also protects the central locking/alarm system, and you didn't mention anything about that not working. Also, if the DME/ECU is not getting power, then the car will not run. Is it possible that the port wires have gotten disconnected either under the dashboard or at the DME/ECU? It does not make sense that the car still works fine but you have no signal at the OBD socket, unless something has become disconnected. Is it also possible for you to try a different OBDII reader in the socket (Auto Zone will do it for free)? Could be they are idiots at the government inspection test station. I would also pull every one of your fuses and check them all...and I would not substitute a 10AMP for a 7.5AMP...stay at the lower 5AMP until you figure out what is wrong or get the correct 7.5AMP fuse. I just crawled under mine (99 996 C2) and clearly, with a flashlight, I can see the wires attached to the socket and can feel them with my fingers run from the socket to behind the carpet on the wall. There are only two small torx screws holding the socket to the underside of the dashboard, so maybe you should drop your socket and check that way.

Joe I took out the screws to the socket last night but was unable to completly remove the socket. Thats what made me ask, 'did the wires come from the socket from the side or the back of it 'and thats what was holding it back from coming completly away for a good inspection. I will hold off for the annual inspection for today and go further into it this afternoon. Maybe ask Auto zone to check for a reading before taking it for the annual. Thanks. A couple more questions Joe. Does the wires come from the back of the socket on yours or from the side and roughly how many wires can you feel/see? and do you know which seat the DME/ECU is located and what it looks like? Would I have to remove the seat to get to it?

Make sure that the connector stays in place. I have to have someone hold it securely by hand for mine to make a connection.

About 10 wires that I could see/feel. They come in from the side and go into the top of the socket. ECU is located behind passenger jumper seat: http://sharkwerks.com/porsche/techni...2-and-gt3.html

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The only time I have come upon an OBD2 connector that failed to "produce a signal" is when I was at a fleet customer's site working with some Ford H-D pickup/van fleet vehicles and some had non-operational OBD2 connectors due to a lack of power at the connector. The OBD2 test equipment I develop requires power and it gets its power from the 12V line at the OBD2 connector. In some vehicles this power line is fused, as it was in the Ford vehicles. What had happened is these fleet vehicles had lots of electric/electronics plugged into the Aux. power connector to power cell phone changer, NAVI unit, two-way radio, and this overloaded the Aux. circuit and blew the fuse. Thus the reason there was "no signal" was not because the DME/ECU was not able to communicate on the OBD2 bus but due to the lack of power the test equipment needed to run in order to establish OBD2 communication with the DME/ECU. If power is present and the ground is good and an OBD2 test device still doesn't work, I can think of a bad pin/connector or a broken wire. An electrical problem not an ECU/DME problem. However faulty wiring can damage a DME/ECU so care wants to be taken when messing (tech term) with this connector and its wiring. Another possible problem is the test equipment assumes the wrong OBD2 protocol. In the case of your 99 I believe the protocol would be either ISO-9141-2 or KWP 2000. Either the test equipment must be set to the proper protocol or it must do a protocol discovery and through SAE/ISO documented steps identify the OBD2 protocol used by the vehicle. IOWs, there was an operator error on the part of the person doing the emissions inspection. Sincerely, Macster.

I pulled the codes out of my '99 with a simple $30 code reader that I got from ebay.

For code pulling, code clearing, and maybe readiness monitor statues a $30 tool is plenty and if the OP wants to get one to see if the car's OBD2 port/connector/wiring is working ok that's a good way. I'd spring for a code reader/data viewer with more features for such a device can prove to be very useful beyond just reading/clearing codes. Sincerely, Macster.

Hey thanks guys. Auto Zone did get a signal from the socket so I then took it to the test centre and guess what... Now I find that I have no reversing lights (Not related) so now I am looking to install or change the back up light switch. It never rains but what it pours I guess. When I DIY that small problem I will return for the Annual Inspection and hopefully it will pass. Will do follow up when thats done. Does anyone know if the back up (reverse light switch) is on the outside of the transmission? I will jack the car tomorrow and check for it.

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Yes, if you have long arms this is an easy replacement. http://www.renntech.org/forums/tutor...lights-switch/

Hey thanks Loren. I can't get the link until I become a member so I am applying. Well I sent an email how to go about joining. Do I get to the switch from under the car or from inside the car?

Like I said if you have long arms you can reach the switch from under the car. The switch is on top of the transmission so you need to reach (or remove the right rear wheel (and still reach).

Well they do not always have the brightest people run these machines. It s agood chance the guy went home and told his wife "what a day, every car I did had no OBD signals, How can so many cars have bad comeputers.. I bet it was that lightning storm last month." or if they are on this forum they will find a way to blame the MAF

++1 Shark Attack....or the IMS/RMS (sigh). What is good is that someone had an issue, asked questions, dug into some technical aspects of their car and discovered some new things. They got pointed in the right direction and figured out their problem. I think the depth and knowledge of the people on here, plus practical aspects of knowing more about one of the most awesome cars on this planet, are well worth it. Figures some government inspection station would screw up! 2 beers in and headed for a nap!

ok done and back up lights working again. I jacked the back up, dropped it onto stands and slid in from the back. Real easy to change out the switch. Total cost $28.. One thing I must tell you which I find very strange. I unlplgged the wires from the switch. Unscrewed it and re connected the wires. Push the button on the swtich and they came on. Put it back in the transmission. reconnected it. Switched the ignition on again, selected reverse and still it didn't come on. Took it to Autozone showed them and he showed me a new switch. The button felt harder to push down. I put that in the transmission and BINGO it worked. I then took the car for it's annual and told them that autozone got a signal from my OBD port. I showed them last years pass which stated my OBD port was not working. They appologized and said that there reader was not working correctly last year. DUH... Long story short. Nothing wrong with my OBD port and the car passed with flying colours. Thanks for all your support guys.

I had a mechanic failed me for an annual inspection once because the airbag light was out. Only it wasn't, he just didn't know how to test it on a Porsche. Pissed me off. Fortunately, I was able to pretty quickly demonstrate he was wrong. Some mechanics are sharp as hell, but not not all of them are the brightest thinkers in the world.