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Troubleshooting tips for Porsche 993

Here is a list of the most common problems and solutions specifically for the Porsche 993

Drive Block
Cars equipped with the Porsche drive block system cannot be diagnosed unless the drive block system is de-activated. The easiest way to do this is to start the car prior to diagnosis. Since the drive block system uses the same communications wire as the diagnoses, when the drive block is active communications is not possible.

Correct interface adapter
Our first generation cables were sold with two different adapters: one for Boxster, 996, Cayenne, 997, and 987; and a second cable specifically for the Porsche 993. The cables for the 993 can be identified by blue and yellow shrink tubing on the cable. All newer style cables that have the light on the connector end will work on all models including the 993. Also, some 1995 models have the 19-pin, round diagnostic connector and require an adapter to work with these cars. The round connectors are NOT compatible with our first generation cables.

Airbag Problems
Many of the original 993 airbag modules were replaced by Porsche with the updated 996 model airbag modules. These new modules have a part number that starts with 996. To access these, select the airbag from the 996 menu.
If the car is equipped with an original 993 airbag module and you cannot connect to the control module, it is likely that the module is bad. When these modules fail, you will not be able to access the airbag module. The original airbag modules were manufactured by MTB and the part number starts with 993.

Wiring problems
Cars that have Radar detectors and other aftermarket electronics equipment installed often have problems with the OBDII connector. Since the connector is in a convenient location for aftermarket equipment these connectors are often used to supply power and ground. Consequently, they no longer have the correct pin assignments.
The correct pin-out for the diagnostic connector is:
Pin 1 = Terminal 15 power(also known as key on power)
Pin 3 = K-Line 2 (communications wire for all modules except engine)
Pin 4 = Terminal 31 ground (very common for the car missing this ground pin)
Pin 5 = Terminal 31 ground
Pin 7 = K-Line 1 (communications wire for engine but is routed through the drive block system)
Pin 15 = L-Line (communications wire for most of the car modules used to wake-up the module)
Pin 16 = Terminal 30 (battery power)

If any of the cars modules are faulty, the bad module can hold the communications wires to ground or positive voltage. This prevents any modules from being accessible for diagnostics.
When testing communications wires, you should make sure you have good continuity from the diagnostic connector to the control module and the communication wire is not shorted to ground or battery power.
It is also common to see cars where the drive block system has been removed and the communications wire is no longer connected to the engine control module.

Heating and Air conditioning Faults
If you request fault codes on the Porsche 993 more than once you will receive each possible fault code instead of only the current faults. The first time you access faults, the faults will be accurate; but in subsequent requests, the control module will return all fault conditions.

DME Fault code reference
When troubleshooting a North American market 1996+ 993 or a 993 Turbo, you will find that the fault codes for the DME do not match the fault codes that are supplied in the factory service manual. To get correct information, you will need to reference the Motronic 5.2 USA OBDII supplement. The normal factory manual references the ROW motronic 2.1 system.

Actual values
When displaying actual values, you should only select one or two values at a time. The original Porsche tool can only display one value at a time.