Air Management - ASC/DME Interface

Vehicles equipped with ASC include additional hardware that also manipulates intake air flow. If the ASC control module detects rear wheel slip exceeding allowable limits, it reduces intake air flow by activating the ADS II actuator which reels in a bowden cable that closes the ADS II throttle plate. The ADS II throttle plate is up stream of the main throttle plate. Regardless of how far the driver is stepping on the accelerator pedal, the ADS II throttle plate reduces the intake air flow which reduces engine power to regain traction.

The ECM is informed when ASC is regulating the intake air flow via the ASC/DME Interface. The interface consists of three signal lines for AS regulation. The three signals are switched high/low input requests for power reduction/drag torque reduction. The signals are:

- S-EML - Signal to the M541.1 Control Module of throttle regulation
- S-MSR (SUAVE) - Signal request to the M541.1 Control Module for ignition timing retard and idle speed boost
- S-ASC (A) - Signal request to the M541.1 Control Module for fade out of ignition/injection and idle speed boost












The ECM also provides the ASC control module of the main throttle plate angle (signal DKI) so the ASC system can modulate the opening/closing angle of the ADS II throttle plate to achieve the correct air volume entering the engine during ASC regulation.







MSR Function:







With Decel fuel cutoff function active, while decelerating in a high gear and on a slippery road surface, the possibility of engine drag torque can occur. Engine drag torque causes the drive wheels to loose traction in the opposite direction during decel and could cause the vehicle to loose stability. The AS system can correct for this condition by detecting the loss of traction during decel and activating MSR.

ASC relies on the ECM to carry out the MSR function. In non EML equipped vehicles, MSR is achieved via the the interface signal to the ECM which opens the idle control valve and cancels decel fuel cutoff. This action accelerates the engine slightly to reduce engine drag torque.