The removal of the 991.1 GT3 RS ECU is fairly straightforward and can be accomplished with a basic set of hand tools and a set of torx bits.
Torx bits and sockets needed:
If you have any questions along the way please feel free to reach out to M-Engineering for help. Info@M-Engineering.us
Please disconnect the negative terminal from the battery before removing the ECU. Leave the battery disconnected as long as ECU is removed. For instructions on how to access the battery consult your owners manual.
Open up the rear deck lid
2. Begin by removing the fan shroud and the two connectors underneath. The fan shroud should pop up out of place easily with little to moderate force. Each fan has a small connector on the bottom side. Disconnect each connector after the shroud is loose.
3. Next remove the small plastic piece to the right which generally has Mobil 1 oil recommendations on it. This piece also will pop out with little force.
4. You can now see part of the ECU and the main harness connector for the rear end lights. Disconnect the harness (Red), You can also remove the little black caps (Orange) that cover the T45 torx bolts we will need to remove later. The black caps are just covers and should come off by hand or with a small prying tool.
5. We can now start to remove the bolts for the tail lights so we can remove the carbon cover. The bolts are T25 and there are four of them (Red). We can also remove the four T27 size bumper support bolts (Orange).
6. This next step requires loosening the oil and coolant fill support piece. There is one 10mm bolt (Red) and the coolant cap will need to be removed temporarily.
7. You can now gently pull the support up and over the retaining slider that can be seen on the right side of the coolant fill. Under where it is circled in red. The next picture also shows it in more detail.
Detailed picture of retaining slider above:
8. With that support loose we can now access all of the remaining T45 bolts to pull the carbon engine cover out (Red).
9. Now that all the bolts are removed we can now take out the carbon engine cover. Since the carbon cover goes slightly under the read bumper you will need to lift the part of the cover nearest the front of the car while sliding it forward. A small bit of messaging will get the piece out without incident.
10. Now we can finally get to the ECU, above circled in red. It is attached in the engine bay by two 10mm nuts that will require a deep well socket to remove. There is one on each side of the ECU pictured below. You can also remove the harness to get better access. There are two connectors that need to be disconnected. Simply pull up on the part that is circled in blue and this will actuate the slider to push the connectors off the ECU.
11. The final step involves disconnecting the ECU case from a small line and harness. The line, pictured below in red, can simply come out of the bracket if pulled down. The other harness attached to the plate, in orange, can be slid down and off the ECU bracket in a downward motion.
Once everything is removed you can then slide the ecu out towards the back of the car and pull it from the engine bay!
Installation is the opposite of removal. Please remember to keep the battery disconnected when the ECU is not installed otherwise some faults may appear after reassembly.