PORSCHE CAYMAN 981 GT4 Engine Control Unit + Key
Porsche Cayman 981 GT4 is a unique “parts bin” masterpiece from Porsche, utilizing the 3.8L flat-six from the 991.1 Carrera S. For this reason, the ECU and security architecture are specific to the 981 GT4’s unique tuning and manual-only configuration.
To have a functioning, swappable set for a 981 GT4, you need to manage the Continental/Siemens SDI 9 (or SDI 21 in some regions) management system.
The 981 GT4 Security Set
Unlike the older 996, a modern 981-generation car requires several modules to “agree” on the security code before the fuel pumps and ignition will trigger. A complete set should include:
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DME (Engine Control Unit): Located behind the carpet in the rear trunk area. Look for part numbers starting with 981.618.XXX.XX.
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BCM 1 (Front Body Control Module): Located under the dashboard on the driver’s side. This is the primary immobilizer master.
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BCM 2 (Rear Body Control Module): Located in the rear. It manages the electrical system and works in tandem with BCM 1 for security.
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Key Fobs: The specific “981” style keys with the GT4-specific transponder ID.
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Ignition Switch (EIS): In the 981 platform, the electronic ignition switch is a “node” in the security chain.
Technical Highlights
| Feature | Specification |
| Engine Code | MA1.23 (3.8L Flat-6) |
| ECU Type | Siemens / Continental SDI 9 |
| Transmission | Manual Only (No PDK logic in GT4 DMEs) |
| Rev Limit | $7,800 \text{ RPM}$ |
Key Identification & Sourcing Tips
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The GT4 Distinction: A standard Cayman S (3.4L) ECU cannot be flashed to run a GT4 engine easily because of the different displacement and the specific variable valve timing (VarioCam Plus) maps used for the 3.8L engine.
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Manual Transmission Mapping: Since all 981 GT4s were manuals, the DME is hard-coded for a manual transmission. This makes these units highly sought after for engine swaps into 981 Caymans or Boxsters that are being converted to the 3.8L powerplant.
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Verification: When inspecting the DME, check for part number 981.618.631.02 (or similar revisions). The label should clearly state it is for the 3.8L engine.
Handling and Shipping
The Siemens SDI 9 units are robust, but the BCM modules are notoriously sensitive to static electricity.
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Packaging: Wrap each module individually in high-quality anti-static bubble wrap.
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Inventory Note: If you are selling this as a “Conversion Kit,” ensure you include the VIN of the donor car; the buyer will need this if they ever need to order a replacement key from Porsche in the future.
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