964 & 993 OBD1 - Pre-MY1996 Cars, Code list and how to read codes.

NOTE: This page is a DRAFT work in progress, may have errors, and the code list is incomplete. It is based on information related to the 964 and assumes the OBD system features were carried over to the early non-USA delivered 993.

The OBD1 systems were first mandated in 1991 and were driven by California regulation. It was the first system where diagnostic system features were mandated. The manufacturers were not required to use a standard interface with code readers. The breadth of information available from OBD1 cars was limited in comparison to the later OBDII compliant vehicles but still very useful in diagnosing emission and other systems issues.

The OBDI emissions-related codes can be read with or without a reader.

Here is how to read codes without a reader*:

(*The below I understand works for a 964 and it follows that it should also work for the pre-1996 OBD-1 993 although I have not tested it for either series of cars. In any event, Durametric software supports all vehicles in both series through the OBD port.)

1. With the engine off turn the ignition switch to the "ON" position.

2. Press the accelerator pedal all the way to the floor for 3-5 seconds.
3. Wait for the "Check Engine" light to flash, then release the accelerator pedal.
The car's computer will begin to flash the "Check Engine" light.
Count the number of flashes between and notice the pause between flashes.

In this case, code 24 is the "Oxygen Sensor"

How to clear codes:

1. With the engine off turn the ignition switch to the "ON" position.
2. Press the accelerator pedal all the way to the floor for 11 seconds.

Porsche 964 & Pre-1996 993 OBDC-I Emission-Related Fault Codes

Here are the modules accessible using Durametric Software & Cable:
1989 - 1994 Porsche 911 (964)

Module	ECU Identification	Information	Read Codes	Clear Codes	Actual Values	Activations	Commands	Coding*
Motronic 2.1 M00 - M04 (Engine)	Yes	No	Yes	Yes	Yes	Yes	No	No
Tiptronic	Yes	No	Yes	Yes	No	No	No	No
ABS / PDAS	Yes	No	Yes	Yes	No	Yes	No	No
Air Conditioning	Yes	No	Yes	Yes	No	No	No	No
Airbag - B01	Yes	No	Yes	Yes	No	No	No	No
Alarm	Yes	No	Yes	Yes	No	No	No	No

Special features for this car:

• Activation for brake bleeding procedure
• Activation for transverse lock

Body Grounding Scuff and Road Debris Paint Touchup

How to minimize Bumper Cover Grounding issues:

If you are regularly grounding your lower front bumper cover/valance/splitters consider raising your vehicles to a height at your next alignment so that the lower bumper cover just clears the typical cement parking block. This is still well below the euphemistically called Stock USA "nose bleed" height and will minimize future grounding.

Here is some information on suspension heights.

Using spray touch-up paint to clean up paint abrasions on the lower parts of a 993:

For my car, a non-metallic Speed Yellow car,  I keep on-hand a can of exact OE color matched spray paint to touch up the occasional scuff just on the lip at the bottom of the leading edge of the lower bumper cover splitter. If your car has a metallic paint finish a little testing in an inconspicuous place on your car may be in order to see if the match is to your liking.

It also works well to touch up the bottom trailing edges of the wheel wells where they are subject to road debris abrasion thrown up by the tires.  All this cover-up is down below the line where the original factory finish has a sort of pebble-like abrasion-resistant coating under the body color paint so the variability of spray paint application seems to blend in without notice. Just a quick masking off around the abrasion and a dusting of added paint and it's done, no biggie. It's so quick and easy it can be added to one's regular car wash duties, reapplying it as needed.

I purchased both a couple of cans of body color & clear-coat, from: 

https://expresspaint.com/ 

they have lasted for many years of spot touch-up.

Also here is some more information on spot touch-up of paint chips, nicks, gouges, and scratches.

Andy                                                Return to home page.