The BMW E46 M3 can refuse to start for various reasons, including a dead battery, worn-out starter, or faulty brake pedal switch. However, sometimes, the issue may originate from the SMG Pump Assembly.
Understanding the BMW SMG Transmission
The BMW’s SMG transmission is a hybrid between a traditional manual and automatic transmission. It features a computer-controlled clutch, operated by hydraulics. Gear shifts can be made using a stick or paddles located behind the steering wheel, eliminating the need for a clutch pedal.
Identifying SMG Pump Failure
The SMG pump failure is identifiable using a computer diagnostics scan tool that reveals a diagnostic trouble code (DTC). A common indicator of a failing SMG hydraulic pump assembly is a problem with hydraulic pressure. The SMG pump, which operates similarly to an ABS pump, controls hydraulic pressures in the transmission. A blown fuse for the SMG pump is a strong indication of pump assembly failure.
Implications of SMG Pump Failure on Vehicle Start
The failure of the SMG pump and the consequent blowing of its fuse results in the loss of control over gear shifts by the vehicle’s onboard computers. The clutch becomes engaged and unusable, preventing the car from starting, even when in neutral. This situation mirrors the inability to start a modern manual gearbox vehicle unless the clutch is fully disengaged.
SMG Pump Assembly Replacement Process
Following the identification of the SMG pump failure, the faulty pump was replaced and the error codes cleared from the onboard computer. A test drive was conducted for quality assurance and to confirm the resolution of the problem, ensuring that the vehicle was functional again.
