The National Highway Traffic Safety Administration said there was one reported fire among the four complaints it has received about the wiring problem.
The agency did not estimate how many vehicles would have to be recalled if the wiring is found to be defective and a safety hazard.
More than 5,000 Porsche 911s were sold in the United States in the 1995 calendar year, according to the Automotive News Data Center.
NHTSA, in its monthly report on possible defects, also said it is upgrading its investigation of airbags in 1994-95 Nissan Altimas from a preliminary evaluation to the more intense category of engineering analysis.
The agency and the vehicles' manufacturer have collected 75 complaints about face and eye injuries to passengers when front airbags deployed in relatively minor crashes. NHTSA said some people had partial or full loss of vision.
There are about 250,000 of the cars on the roads, the agency said.
NHTSA closed one investigation after finding insufficient evidence that a defect exists. It had been opened because of complaints that stop- lamps overheat in 1997-99 Chevrolet Malibus.
The agency closed other cases after manufacturers agreed to conduct safety recalls. They had been opened because of complaints about the following: