Alarms / Security / Central Locking

Signal Transducer (Impedance Converter).
The Porsche signal transducer, also known as an impedance converter, processes ignition-key transponder information for the alarm/immobiliser control system.

Fits:

• Porsche 996 C2 3.4L 1997–08/01
• Porsche 996 C4 3.4L 1997–08/01
• Porsche 996 C2 3.6L 09/01–2005
• Porsche 996 C4 3.6L 09/01–2005
• Porsche 996 C4S 3.6L 09/01–2005
• Porsche 996 TURBO 2000–05
• Porsche 996 GT2 2001–05
• Porsche 996 GT3 MKI 1999–02
• Porsche 996 GT3 MKII 2003>>
• Porsche 996 GT3 RS 2003–04
• Porsche Boxster 986 2.5L 1998–99
• Porsche Boxster 986 2.7L 1999–02
• Porsche Boxster S 986 3.2L 1999–02
• Porsche Boxster 986 2.7L 2003–04
• Porsche Boxster S 986 3.2L 2003–04
• Porsche Carrera GT 2003–06

Diagram Ref No 5

Check fitment for your specific vehicle (model, year, engine) before ordering.

What Is This Part?
This is an electronic signal-conversion component in the ignition-key recognition system. It obtains the transponder code from the received signal and passes that information to the alarm control unit. The control unit uses the key information as part of the immobiliser authorisation process. The converter is therefore a relevant component to test when an otherwise correctly matched ignition key is not being recognised.

What Does This Part Do?

• Processes the transponder signal: Obtains the key identification code from the signal received through the transponder-reading circuit.
• Passes on key information: Sends the transponder code to the alarm control unit for recognition.
• Supports start authorisation: Provides key information used by the immobiliser system when determining whether starting is permitted.

Why Replace This Part?
Replacement may be appropriate when electrical testing confirms that the converter no longer processes or passes on the transponder signal correctly. Damage to its housing, mounting or electrical connection may also justify renewal if it prevents secure installation or reliable contact.

A starting fault alone does not identify this component as the cause. Battery condition, the key transponder, reader coil, wiring and alarm control unit should be checked before replacing the converter. Intermittent faults need particular care: a poor connection elsewhere in the circuit can produce similar symptoms, so the cause should be established before parts are changed.

When to Replace This Part?

• Confirmed conversion fault: Testing identifies a failure within the converter rather than elsewhere in the key-recognition circuit.
• Intermittent key recognition: Diagnostic checks trace inconsistent recognition to this component or its electrical connection.
• Damaged housing or mounting: The unit cannot be retained securely in its intended position.
• Deteriorated connections: Terminals are damaged or corroded and cannot be satisfactorily repaired.
• Damage found during related work: Inspection during ignition-lock repairs reveals a defect affecting the converter's installation or operation.

Where Is This Part Fitted?
Location: At the ignition steering-lock housing, behind the dashboard. It forms part of the electrical connection between the ignition-key transponder reader and the alarm/immobiliser control system.

Product Summary

• Product: Signal transducer / impedance converter.
• Brand: Porsche.
• Part number: 99661815901.
• Purpose: Processes ignition-key transponder information for the alarm/immobiliser control unit.
• Installation: Ignition steering-lock housing.