ECM Relay

ECM Relay

The ECM (C0604) provides an earth path for the ECM relay coil (C1895) on an N wire. The energised relay (C1895) provides a feed to fuse 2 of the engine compartment fuse box (C0570) on an RW wire. Fuse 2 (C0570) is connected to the EAT ECU (C0932) by a pair of RU wires.

For more details on ECM relay operation, refer to the Engine Management System – Td6 section of the System Description and Operation Workshop Manual.

EAT ECU

The EAT ECU controls operation of the transmission via the following:

Pressure Regulator Solenoid

The EAT ECU (C1835) provides a Pulse Width Modulated (PWM) signal to the pressure regulator solenoid (C0244) on a P wire. This enables the pressure regulator solenoid (in conjunction with the pressure regulator valve) to control line pressure supplied to the clutches and shift control valves. The EAT ECU (C1835) provides an earth path for the pressure regulator solenoid (C0244) on an R wire.

Torque Converter Clutch (TCC) Solenoid The EAT ECU (C1835) provides a PWM signal to the TCC solenoid (C0244) on a G wire. The TCC solenoid is a normally closed solenoid, and controls the output fluid pressure to the torque converter clutch. The EAT ECU (C1835) provides an earth path for the TCC solenoid (C0244) on a BY wire.

Shift Control Solenoids

The EAT ECU (C1835) provides a PWM signal to the three identical shift control solenoids (C0244) on a G wire. The EAT ECU (C1835) provides an earth path for solenoid A (C0244) on an OB wire, solenoid B (C0244) on a GR wire, and solenoid C (C0244) on a Y wire. For details of solenoid opening and closing, refer to the Automatic Transmission – GM 5L40– E section of the System Description and Operation Workshop manual.

Input Shaft Speed Sensor

The EAT ECU (C1835) provides a feed to the input shaft speed sensor (C0244) on a U wire. The input shaft speed sensor (C0244) returns an ac voltage pulse back to the EAT ECU (C1835) on an O wire. By measuring the peak to peak voltage of the voltage wave form, the EAT ECU can determine the speed of the input shaft.

Output Shaft Speed Sensor

The EAT ECU (C1835) provides a feed to the output shaft speed sensor (C0244) on a W wire. The output shaft speed sensor (C0244) returns an ac voltage pulse back to the EAT ECU (C1835) on an N wire. By measuring the peak to peak voltage of the voltage wave form, the EAT ECU can determine the speed of the output shaft.