Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
2021 BMW M2 Standard TransFACTORY OEM SERVICE PROCEDURE
12 90 E-Box
N55 ENGINE (2016-2018):
12 90 ELECTRONICS BOX, WIRING HARNESS - TIGHTENING TORQUE SPECIFICATION
| Type | Thread | Tightening specifications | Dimension | |
|---|---|---|---|---|
| 1AZ Cable channel to cylinder head cover | N55/N55 Hybrid | 8 Nm | ||
| 2AZ Earth cable to crankcase lower section | N55/N55 Hybrid | M8 | Replace aluminium screw. Jointing torque Angle of rotation |
8 Nm 45° |
| 3AZ Earth cable to rear cylinder head | N55/N55 Hybrid | M6 | 8 Nm | |
| 4AZ Cable channel to engine block | N55/N55 Hybrid | M6 | Replace aluminium screws. | 8 Nm |
| 5AZ Earth cable for ignition coils | N55/N55 Hybrid | 5 Nm |
S55 ENGINE (2019-2022):
12 90 ELECTRONICS BOX, WIRING HARNESS - TIGHTENING TORQUE SPECIFICATION
| Type | Thread | Tightening specifications | Dimension | |
|---|---|---|---|---|
| 1AZ Cable channel to cylinder head cover | S55 | 5 Nm | ||
| 2AZ Wiring harness to cylinder head cover | S55 | 5 Nm | ||
| 3AZ Earth cable to rear cylinder head | S55 | M6 | 8 Nm | |
| 4AZ Cable channel to engine block | S55 | M8 | 19 Nm | |
| 5AZ Ground cable for ignition coils | S55 | 4.6 Nm | ||
| 6AZ Holder on intake plenum | S55 | 4.5 Nm |
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.