The E46 M3 SMG cog light error code 54 (0x36) often arises due to the SMG pump’s inability to maintain appropriate system pressure. This error denotes an exceeded pressure range detected by the system’s pressure sensor. The sensor signals that the system pressure is uncontrollably high, which persists even when the pump is de-energized.
Several factors can contribute to this issue, listed below in their typical order of occurrence:
- A damaged high-power relay (salmon relay) can become unreliable over time, not adhering to DME instructions by remaining in either an ON or OFF position. This malfunction can trigger two specific codes:
- If stuck in the ON position, the SMG pump will continue running, leading to potential overheating and burnout of the SMG pump motor, which can also trigger the 54 (0x36) error code.
- If stuck in the OFF position, the SMG pump won’t prime to build up the required pressure, potentially triggering the 53 (0x35) error code.
- A defective pressure sensor can provide an incorrect system pressure reading to the DME.
- Damage to the wiring harness, which can happen if the relay gets stuck in the ON position, overheating the wire harness. This can damage the insulation, causing the pump to run continuously.
