Models: E53 X5, E46, E39, E36 - Z3
3.0 and 2.5 Liter
SOP: 3 liter - 4/00, 2.5 liter 9/00
Purpose of the System
The M54 engine was developed to meet the needs for ULEV compliancy for emission control.
The increase in displacement allows the engine to fit the X5 All Roads vehicle while still meeting the demands for power and performance.
EDK Feedback Signal Monitoring & EDK Failsafe Operation
- The EDK provides two separate signals from two integral potentiometers (Pot 1 and Pot 2) representing the exact position of the throttle plate.
- EDK Pot 1 provides the primary throttle plate position feedback. As a redundant safety feature, Pot 2 is continuously cross checked with Pot 1 for signal plausibility.
- If plausibility errors are detected between Pot 1 and Pot 2, MS 43.0 will calculate the inducted engine air mass (from HFM signal) and only utilize the potentiometer signal that closely matches the detected intake air mass. The MS 43.0 uses the air mass signalling as a "virtual potentiometer" (pot 3) for a comparative source to provide failsafe operation. If MS 43.0 cannot calculate a plausible conclusion from the monitored pots (1 or 2 and virtual 3) the EDK motor is switched off and fuel injection cut out is activated (no failsafe operation possible).
- The EDK is continuously monitored during all phases of engine operation. It is also briefly activated when KL 15 is initially switched on as a "pre-flight check" to verify it's mechanical integrity (no binding, appropriate return spring tension, etc). This is accomplished by monitoring both the motor control amperage and the reaction speed of the EDK feedback potentiometers. If faults are detected the EDK motor is switched off and fuel injection cut off is activated (no failsafe operation possible). The engine does however continue to run extremely rough at idle speed.
- When a replacement EDK is installed, the MS 43.0 adapts to the new component (required amperage draw for motor control, feedback pot tolerance differences, etc). This occurs immediately after the next cycle of KL 15 for approximately 30 seconds. During this period of adaptation, the maximum opening of the throttle plate is 25%.
Functional Overview
The DM-TL is located in the drivers side rear wheel well in the X5 and next to the charcoal canister on the E46 - M54.
Scheme 420
- In it's inactive state, filtered fresh air enters the evaporative system through the sprung open valve of the DM-TL.
- When the DME activates the DM-TL for leak testing, it first activates only the pump motor. This pumps air through a restrictor orifice (1.0 or 0.5 mm) which causes the electric motor to draw a specific amperage value. This value is equivalent to the size of the restrictor.
- The solenoid valve is then energized which seals the evap system and directs the pump output to pressurize the evap system. The evap system is detected as having a large leak if the amperage value is not realized, a small leak if the same reference amperage is realized or no leak if the amperage value is higher than the reference amperage. (Scheme 420): Identifying Functional Overview Diagram
M54 System Operation
The pump draws air through its own air filter and delivers it to both exhaust manifolds through a non-return (shutoff valve). The non-return valve is used to
- Control air injection into the exhaust manifold - A vacuum controlled valve will open the passageway for air to be injected once a vacuum is applied.
- Prevent possible backfires from traveling up the pipes and damaging the air pump when no vacuum is applied.
The control module activates the vacuum vent valve whenever the air pump is energized.
Once the vacuum vent valve is energized a vacuum is applied to the non-return valve which allows air to be injected into the exhaust manifold. A vacuum is retained in the lines, by the use of a check valve, in order to allow the non-return valve to be immediately activated on cold engine start up. When the vacuum/vent valve is not energized, the vacuum to the non-return valve is removed and is vented to atmosphere.
