Lesson 1, Topic 1
In Progress

ECU Removal (Engine Control Unit)

LocationThe ECU is located under the bonnet, behind the battery on the right-hand side (whilst facing the car).
2021 Regulations Reference5.7.7
Parts to DiscardNone
Important ChecksCondition of the mounting plate, bolts and electrical connections/pins.


Do this as a priority, your ECU needs to posted and reprogrammed by Hybrid Tune so don’t delay.

When removed (using a permanent marker) write your name, car make and race number (if you have one) onto the back of the ECU. See this link for full instructions and details https://citycarcup.co.uk/ecu-instructions/

Suggested Disassembly Method (6 Steps)

Step 1. Disconnect the battery as described in the ‘battery removal’ lesson. Here a quick note and some reminders in the meantime. Disconnect the earth/negative (black) cable clamp first, when refitting replace the negative cable last, think ‘negative first off and last on’. Isolate the battery terminals if leaving the battery in place. Once ready remove the battery tray clamp (secured with 1 bolt) from the battery tray and lift out the battery.

Step 2. Remove the top of the fuse box (lid) to gain better access and view of the ECU, then locate and remove the upper right and lower left bolts holding the fuse box in place for any given period.

Step 3. Prise the plastic securing clip as illustrated on the bottom right and lift the fuse box up and to the right. The fuse box will not move very much as it is still connected to the wiring loom, but this will give you better access to the ECU mounting frame located behind.

Step 4. This now reveals the ECU, note the cable ties securing the ECU harness connectors in place, remove these carefully with wire cutters. Now use a small screwdriver to pull/prise outwards the connected security clips on either side as illustrated.

Step 5. Remove the ECU wiring harness connections by lifting them carefully from the ECU.

Step 6. Having disconnected the ECU wiring harness conenctions you are now able to remove the 4 ECU mount bolts.