Code 1112: Idle Speed Switch Short Circuit To Ground

1. Disconnect DME control unit. Connect DVOM between terminal No. 24 (ground) and terminal No. 52 (idle speed switch). See Fig 1 . With throttle valve closed, resistance should be less than 10 ohms.
2. Open throttle valve beyond one-degree opening angle. With throttle valve open, ohmmeter reading should be infinite. If readings are incorrect, measure resistance directly at idle speed switch and adjust if necessary. See ADJUSTMENTS article.

Fig 1: DME Control Unit, Fuel Injector & Oxygen Sensor Connector ID

Courtesy of PORSCHE OF NORTH AMERICA, INC.