News Technical Service Bulletins

Porsche Power Supply Caution

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This bulletin applies to 2011-2015 Porsche Cayenne vehicles. If the low voltage limit of a module is reached, fault codes may be stored and the module may shut down with little or no warning. The low voltage limit and shutdown behavior also differ between modules. If a low voltage condition occurs while being programmed, communications between the PIWISI Tester and the module will be lost and the module may be rendered permanently inoperable. 

The electrical system of a well-equipped vehicle can draw more than 40 AMPs of current with the ignition switched on. It is important that a clean microprocessor-controlled power supply be connected to a vehicle whenever the ignition is switched on and the vehicle’s engine is not running. Never use an unregulated, high output battery charger on these vehicles. 

The power supply must have a minimum continuous output capability of 40 Amps at 13.8 VDC under load. With the ignition switched on, the output of most power supplies will be 14.2 to 14.5 VDC. A vehicle voltage below 13.8 VDC under load may indicate that the capacity of the power supply has been exceeded. The voltage supplied to the vehicle must never exceed 14.5 VDC for more than a few moments. A sustained voltage above 14.5 VDC will dry out and permanently damage the glass mat in the cells of the AGM battery.

While programming modules: Never run the engine instead of or while using an external power supply. Never interrupt power supply connections of disconnect the vehicle battery. Never operate any electrical system (audio, climate control, power seats, door latches, etc.). Never enter or exit an air suspension vehicle, which may cause the system to activate.


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