Porsche Cars North America, Inc.
100 West Liberty Street
P. O. Box 30911
Reno, NV 89520-3911
Dear Mr. Love:
This responds to your request for an interpretation of Federal Motor Vehicle Safety Standard No. 102, Transmission shift lever sequence, starter interlock, and transmission braking effect. You asked how the requirement in S3.1.4 concerning display of shift lever positions would apply to the Porsche Tiptronic transmission in the event of a serious fault in the transmission. As explained below, the vehicle would not need to meet S3.1.4 when it detects a serious fault in the transmission.
In your letter and in a telephone conversation with Dorothy Nakama of my staff, you explained that the Tiptronic transmission has a default "limp-home" mode which is enabled whenever a serious fault is detected in the transmission control unit. In this mode, the vehicle automatically goes into fourth gear drive. This allows the driver to get the car to a dealership where the fault can be repaired. If the driver attempts to move the shift lever, the vehicle's transmission would not go out of fourth gear. However, the driver would be able to put the vehicle into "park." You stated that Porsche plans to indicate to the driver that the transmission has entered the limp- home mode by flashing alternately the gear position indicator and the gear number indicator.
S184.108.40.206 of Standard No. 102 states that:
[I]f the transmission shift lever sequence includes a park position, identification of shift lever positions, ... shall be displayed in view of the driver whenever any of the following conditions exist:
(a) The ignition is in a position where the transmission can be shifted.
(b) The transmission is not in park.
The question you raise is similar to one we addressed in a July 29, 1993 interpretation to Mazda (copy enclosed). In both situations, NHTSA is asked to address whether, in an abnormal functioning of the vehicle, the vehicle must continue to meet Standard No. 102. In the letter to Mazda, we stated that Standard No. 102 presumes a functioning vehicle with a functioning gear shift lever sequence. One of the purposes of Standard No. 102 is to reduce the likelihood of shifting errors. In the letter to Mazda, NHTSA went on to state:
In the event of a power failure in a vehicle incorporating electronic transmission gear shift sequence displays, the vehicle would not be capable of being driven, or of having its gears shifted. Therefore, since the standard did not contemplate driving or shifting gears in the event of a power failure, the standard was not intended to regulate the transmission shift display in the event of an electrical or other power failure, when the vehicle is taken out of the "park" position in order to be towed.
Similarly, in the event of a fault in Porsche's Tiptronic transmission, as you indicated to Ms. Nakama, the vehicle would not be capable of being driven above the fourth gear, or of having its gears shifted. Since Standard No. 102 presumes a normally functioning vehicle, in the event of a fault in the Tiptronic transmission, the vehicle need not meet Standard No. 102's requirement that the "identification of shift lever positions, including the positions in relation to each other and the position selected, shall be in view of the driver."
I hope this information is helpful. If you need any further information, please contact Dorothy Nakama of my staff at (202) 366-2992.
Samuel J. Dubbin Chief Counsel