System outputs

The transmission receives the information every 50 ms (assuming the GIU is not reporting any fault information). If a fault occurs with a transmission input, the ECM receives a fault message. It then knows that the next piece of data it receives will give more information on the fault and not the usual transmission switch status. This effectively means that the ECM receives transmission status information every 100 ms and fault information every 100 ms both at 50 ms intervals.

The GIU sends the ECM information on the following:

• The current status of the park, reverse, neutral and drive switches
• The current status of the sport/manual switches
• The current status of the +/– switches (steering wheel, MGF)
• The current status of the +/– switches (selector lever)
• Fault status
• Brake switch input

System outputs

The following section details the units controlled by the ECM, either directly, or via outputs in the form of messages which control or provide information to other systems:

• Indicator lamps/display
• Engine information to GIU

Indicator lamps/display

The ECM will illuminate a warning lamp/display for the following functions:

• A transmission warning if the ECM or the GIU reports a fault
• The current position of the park, reverse, neutral and drive switches
• The virtual gear position when the vehicle is in manual mode
• A display to indicate when sports mode is selected

Transmission interface

The ECM provides information for the transmission ECU via a PWM bus. The ECM controls the position of the ratio control motor indirectly (by means of instructing the GIU to control the motor to a given position).

The ECM can interrogate the GIU for fault diagnostics and to request real time data and system performance checks when the vehicle is connected to TestBook.

Transmission control strategy

The transmission control is incorporated into the ECM. The ECM does not control the transmission ratio directly but does provide all of the intelligence relating to the required position of the ratio control motor, it also provides the intelligence for how fast it should be operated.

The ECM controls the transmission in one of four modes: 1. Em-CVT mode (normal driving) 2. Em-CVT sports mode 3. Manual mode 4. Fault mode