cobalt

I posted this on the turbo forum but no responses I am assuming being alarm and OBD related it is a common topic. I did use the useless search function, google but I have no answers to my question.

​​​​​​I am helping a friend with an early 96 the 19th vin in the sequence. The car has a lot of gremlins albeit a solid car. A true 58k miles. It wears early exhaust tips and shifter.

When I go to plug in an OBDII scanner into the port on the center console I can't get a connection with any of the hand held scanners I have. The car has alarm issues I believe I need to pull the brains and send them out to ECU Dr to have repaired. One minute. it works perfectly but if it sit for any length of time it won't accept the signal from the key fob. If I unlock the car by setting off the alarm and holding the key to the left for 40 seconds the alarm silences and you can drive the car for a while but eventually the immobilizer will kick in and not turn off. Key fob batteries are new and all is functioning properly 50% of the time.

I will try to barrow a durametric or Altel I might even have access to a PIWIS. My concern is this might be like a few other very early 96's I have come across that had OBDII ports but needed an OBDI scanner or cable to convert to the OBDI round connector. If the ECU is not connecting it could be another problem but before I pull the seat out (which appears to have never been removed) and start drilling I was curious if anyone knows if these cars came with OBDI or OBDII and if the alarm is anything I can work with if I have a proper scanner?

I have never had an alarm problem like this but most of my electrical stuff I work on is not alarm based and I prefer the 964's for this reason. FYI someone pulled the radio and cut the harness. I was planning on installing a PCCM radio but I want to make sure this alarm issue is dealt with first.

Thanks in advance
Anthony

ToreB

The question of OBD1 or OBD2 protocol is not really valid for the 993. The diagnostic protocol was continuously developed at that time, and some called the early functions "OBD1". Most off-the-shelf diag tools will be a waist of money. It would at best be able to connect to the engine control unit, and maybe the ABS,with a lot of limitations. Only a handful of systems that can do all the OBD-connected things in our cars. (Motronic, ABS, air bag, alarm and climate control)

*The Bosch Porsche "hammer" (KTS 301) or later Bosch Porsche tools as PST2, KTS500 or PIWIS v1 or v2
*Freeware Rennlist Scantool Windows software (a serial port adapter as my T-OBD needed)
*Durametric Windows software with a proper serial cable
*Jenniskens OBD UDT/PDT999 diagnostic tool

Cheers,
Tore

systemsc

Most likely it's not an OBDII protocol, and requires a Porsche Hammer/PST2 tester or a Durametric.

The alarm and immobilizer ECUs are very reliable and rarely fail. The typical problem is a poor range from a key fob (remote). The immobilizer can also have a similar problem.
A Porsche PIWIS tester won't function well because it has problems with pre-2000 Porsches.

Read here about the 993 alarm & immobilizer ECUs under Porsche/Alarm/Immobilizer here; https://www.systemsc.com/problems.htm

ToreB

Loren, I agree on the on your notes of failure.
The PIWIS details are interesting, I have heard that PIWIS version 1 and 2 works OK with the classic car models, but version 3 has no classic model support. (928/944/968/964/993)
Do you know anything about this?
Cheers,
Tore

systemsc

PIWIS II has problems re-flashing/coding with 996/986 vehicles.

Yes, PIWIS III is not recommended for early Porsches.

pp000830

Hi Anthony,
--Check the battery. Is it 12.6 or greater volts a rest shortly after turning the car off and 13.5~ 14 Volts when running? A weak battery, alternator, or even an alternator with a loose alternator belt can be an issue not allowing for the Motronic controller or OBD function to work reliably.

--If the car is an OBDII car it should have oxygen sensors before and after the catalytic converter. If it was a USA-delivered car manufactured in 1996 and sold in the US it must be an OBDII car.

--Certain inexpensive readers can read the basic emission-related codes but none beyond this. If the car has the rectangular OBD Port, not the round one, my understanding is no plug adapter is needed for OBDI or OBDII.
https://993servicerepair.blogspot.co...bdc-notes.html

--Clean the plug and socket for the OBD Reader with a little spray electronic cleaner. A dirty connector can interfere with the reader making a communication handshake.
--Last but not least if the ignition immobilizer is active the car won't start and the diagnostic port will not work.
Unlikely your controller is bad, but you can have it tested.
--If the starter turns over the engine but is does not continue to run, or it just stops running while driving consider replacing the Motronic ECU relay a known issue with our cars.
https://993servicerepair.blogspot.co...-why-your.html

Andy

cobalt

I agree as I can borrow a PIWIS 3 since they paid for all models but it doesn't work on air-cooled cars. I have a KTS301 hammer but I would need to source conversion cable from round connector to smaller square one and think it will be useless. It is relatively useless on my 964's.

It looks like i am going to try to borrow a Durametric or possibly have access to a PIWIS one. The Altel usually works on 993's but apparently not this one.

This is what I don't get. The transmitter appears to be working perfectly. When it works it works from 15-20 maybe more feet away. If I click the fob a hundred times lock wait unlock wait lock etc it will work flawlessly. If I test it for 5 min or an hour it works fine. It isn't until I leave it for a half hour +/- that it times out and will not function.

I read your very nice write up long before posting along with many suggestions regarding changing capacitors and other fixes that I am not so sure apply. The car clearly has never seen moisture and the only wiring issues I see are radio related. All other contacts have been tested and work. My bigger concern is not being able to read the ECU but I rarely deal with these and aren't systems on my cars. I even brought in a friend who is Porsche employed air-cooled tech and he is scratching his head with this one. He had just gone through three similar situations he was easily able to diagnose but no luck here with this one.

AFAIK I eliminated the key fob from the equation. Although I don't have the immobilizer code and the key is recut only one key and fob at this time. The light on the fob works without flashing and if the signal works some of the time I have to assume once something times out it is where the issue lies. So I am leaning towards the immobilizer as you mention it might not be receiving the signal. WIthout the code I want to be careful not to make things worse and I am getting resistance from my son who works for Porsche saying they can't seem to access that info anymore for some reason. He is working on it though.

cobalt

Andy,

I hate to say been there done that. New car battery and is on a tender with the front latch locked. New remote battery. Cleaned all contacts with electric contact cleaner. Replaced the burnt out bulb in the frunk. Your bold text is something that did not register however the alarm was in off and no immobilizer light was on when we tried to read it. I have had a situation once where we had an OBDI car with OBDII port but it was a late 95 not a 96 like this one and i needed a cable to use my KTS301. I have to put the car up on the lift but I believe I only saw a single O2 sensor. I will lift and check to see if I need to replace 1 or 4 sensors. After so many years this thing is sluggish off the line and i think it is fouled O2 sensors causing it.

This might be the first thing I haven't been able to resolve on my own with these cars. In all honesty I might consider ripping everything out and going with an aftermarket alarm. The system is foolproof. Neither you or the thief can drive off with it LOL. At least I don't feel bad when I have Porsche trained tech scratching his head.

ToreB

I see no reason to use contact cleaner in this.
An activated Porsche Drive Block immobilizer will inhibit OBD connection to the engine control unit only, not the other units connected to the OBD bus. (ABS/alarm/Airbag/CLimate)
Cheers,
Tore

jay@EZimmoblock.com

IMMO light being out is no guarantee the immobilizer is disarmed. Armed or disarmed, the light will always be out no later than 20 seconds after ignition ON. Check the light 2 seconds after ignition ON. If it goes out, the immo is disarmed and the connection between the OBD port and ECU will be made inside the immo.

cobalt

Actually the immobilizer light is either on or off no inbetween. If I leave the key in the ignition for a min or 30 still on. Only when it is out will the car start. This only happens after setting off the alarma nd using the key to disarm. Once disarmed I can get in and start the car. I have the test procedures I tried as well . Lock unlock lock then open door etc did nothing.

I'm getting no connection to anything in the car period through the OBD port

jay@EZimmoblock.com

Let me see if i understand....You turn the key ON (and leave it ON) and the immo light stays on indefinitely? OR.. You turn the key ON then OFF but leave it in the ignition and the immo light stays lit indefinitely?
Neither of these should happen.
Someone can check on another 96 but on my 97 it goes off after 2 seconds if immo is disarmed and goes off after 15 seconds if the immo is disarmed.

systemsc

Read post #9, i.e. any Porsche capable tester should be able of communicating with all the other ECUs, unless there's a problem with the "K" or "L" comm lines.
I've worked on 993s where an ECU, e.g. CCU, ABS, has hung-up one of the comm lines, or there were wiring problems.
You should have an OBD 16 pin breakout box and a scope to check the 16 pins, e.g. pin 1 & 16 are 12V for Porsche testers. Pin 7 is the "K" line and Pin 15 is the "L" line, and Pin 4 is ground.

cobalt

So when the car is working properly the key in ignition turned on the light comes on and shuts off after 15 seconds or so. I can use the remote to arm and disarm or start the car no issues.

Once 15 or 20 min goes by the car will lock out the remote. Nothing happens and when I put the key in the ignition the IMMO light comes on and stays on. The remote will not function and the light remains on all other lights work and the car will not start. Once this happens the IMMO light will stay on indefinitely and I am locked out of the system. Key fob lights but does nothing and car will not start. The only way to get the car to work again is to lock the car set off the alarm and use the key in the door lock and hold to the left for a period until the alarm shuts off and then the IMMO light comes on for a few seconds and turns off and everything works properly for as long as I play with it. The car will start now for as long as I keep the system from locking or timing out.

I believe I explained that properly and I appreciate the time to diagnose with me.

Jay
I was considering your system but will it help here?

cobalt

I will look into it. I get power when I connect the testers. When the system searches for the DME they all come back connection attempt failed. I cannot get a connection period to the ECU immobilizer activated or not. It might be my readers are too new or too old. The Altel usually can read or connect to most anything. Not necessarily help but at a min give me an eprom message . I am trying to barrow a durametric or a system my friend has that should read just about anything but it might be a few days.