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HomeTech Articles > 993 Technical Article:

Pelican Guest Technical Article
Permission to publish this article is provided generously by
Robin Sun at www.p-car.com
Be sure to visit his site for loads of 993 info!

 How to change to a performance tuned CHIP 
(Only for a 95 993 6 speed)

Caution: When handling electronic components please observe the proper anti static rules, wearing a latex rubber glove will be the least you can do.  Move the driver's side seat all the way back to reveal the two hex bolts that secures the driver's seat to the floor. 

Once the front bolts have been removed, move the seats forward to reveal the 4 rear mounting bolts.  It would be safer to use a hex socket to remove these bolts instead of using a allen key, you would have a higher chance of stripping the bolts with an allen key. 

Some said it is not necessary to take the seat off to get to the OBC, but since I am installing a 5 point harness next the seat had to come off any ways.  Once the seat is off remove the 4 bolts that bolts the OBC onto the floor, and unclip the wiring harness. 

Turn the OBC upside down and pry up the tabs that secure the cover in place. 

Turn the OBC around and remove the cover, and locate the EPROM chip.  Remove the plastic cover on the top of the EPROM chip by inserting a flat screw driver in the slot on the side. 

Using a flat screw driver carefully pry up the EPROM chip, at this time please carefully note the half circle slot on the top of the chip, the new chip will need to go back in the same direction.  Here is a picture of an old and new chip.

Reinstall the cover, bend back the metal tabs on the cover.  Install the OBC mounting bolts and the wiring harness, and you are done. 

Todd Campbell made the below contribution after his experience to replace the PROM chip in his 95 993 Tiptronic, the difference here being that his car is equipped with a Tiptronic transimission. 


This is what is listed on your site regarding Chip replacement for a 95 993:

“Some people have said it is not necessary to take the seat off to get to the OBC, but since I am installing a 5 point
    harness next the seat had to come off any ways.   Once the seat is off remove the 4 bolts that bolts the OBC onto the floor, and unclip  
    the wiring harness. “

Well, in my case, a 95 993 with Tiptronic transmission, after I removed the seat, I was presented with an aluminum shroud that covers all of the wiring harness for the DME and is held one with 4 security bolts.   (Also note that my DME is actually mounted facing the opposite direction than the picture on your site indicates.  My wiring connector is also relocated) These also hold down the DME and the Tiptronic computer (also in this area is the alarm brain—referred to elsewhere as the immobilizer).  The only way I could get the DME out was to drill out the four security bolts.  While this poses a challenge somewhat due to location it also makes an incredible mess under the computer wiring.  If I were to do it again, I would use a vacuum cleaner while I drilled the security bolts.  This would at least help with the metal shavings.  I would also need a third hand—or a helper.

Anyway, the security bolts are threaded in (not riveted) and this may make it easier to ultimately remove the shroud (i.e. by finding a method to create a head that would take a flat head screwdriver for example). I ended up removing the pan that the DME, alarm and Tip computers are on and cleaning out underneath the area.  I also then removed the remnants of the security bolts and replaced these with standard 6 mm x 30 bolts and washers, and reinstalled the pan, computers and ultimately reinstalled the shroud to keep it factory.

Attached are some images that show the shroud.


Todd Campbell

E-mail Todd Campbell

Comments and Suggestions:
Ray Comments: When replacing chip on my 1998 porsche carrera, how many horse do I stand to gain?
August 14, 2016
  Followup from the Pelican Staff: Depends onthe chip manufacturer. http://www.pelicanparts.com/cgi-bin/ksearch/PEL_search_2014.cgi ?SUPERCAT_FLAG=Y&make=POR&command=DWsearch&please_wait=N&SECTION_FILTER=fulinj&description=chip%20 - Nick at Pelican Parts  
Cochino214 Comments: I have a 95. 993 the immobilizer sucks i want to remove all together i dont care about alarm function how can i do it chip and jumper.
April 28, 2015
  Followup from the Pelican Staff: I don't think you can. I would check with a Porsche dealer. - Nick at Pelican Parts  
jamestennier Comments: Mentioned once was the immobilizer. Mine drives me nuts! Why did Porsche not allow me the choice/ responsibility of setting the alarm/ immobilizer on or off as I see fit. Locking the car every time I shut off the engine and then remembering to "unlock" before attempting to start again with an unlighted ignition switch hid behind the steering is a real pain in the ass.
Any suggestions on a permanent fix for this frustrating "attribute" of my '96 993 Carrera would be appreciated.
Also; I am old having driven standard shift over many years, yes I chose a Tiptronic and would not hesitate to make that choice again and again.
January 7, 2015
  Followup from the Pelican Staff: Immobilizer can't be adjusted, as it is for preventing drive away theft.

I think the door lock setting can be adjusted using a Porsche scan tool. - Nick at Pelican Parts
bob Comments: does Pelican sell chips and if not, do you recommend or NOT recommend some suppliers?
October 4, 2014
  Followup from the Pelican Staff: We have chips for some brands and models. Give our parts specialists a call at 1-888-280-7799. They can help you find the right part.
- Nick at Pelican Parts
adammarkevans Comments: How long does it take for the engine to adjust to the new chip?
June 22, 2010
  Followup from the Pelican Staff: It depends upon the year. The cars that actually use a new "chip" should respond immediately. - Wayne at Pelican Parts  
jerzy Comments: I have 97 993 C4S and I was told that EPROM chip is soldered
instead of going into socket.What do I do, also where can I get the new EPROM?
September 25, 2009
  Followup from the Pelican Staff: You need to upgrade the computer using a Porsche tool that can re-write the flash memory. Not exactly an easy job. - Wayne at Pelican Parts  
david3299 Comments: Once the EPROM is replaced. How would you know if the new program is effective and Is the HP increase felt?
July 3, 2009
  Followup from the Pelican Staff: You can do before and after dyno tests, but other than that, I'm not sure of any particular way to measure. Some new programs for the iPhone can act as dynos measuring acceleration, which is a function of horsepower. - Wayne at Pelican Parts  

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