Electronic Automatic Transmission (EAT) - GM5

ELECTRONIC AUTOMATIC TRANSMISSION (EAT) - GM5

DESCRIPTION

General
The GM 5L40-E transmission is an electrically controlled, five speed unit and is mated with the Td6 diesel engine. The transmission is controlled by an Electronic Automatic Transmission (EAT) ECU which contains software to provide operation as a semi-automatic 'Steptronic' transmission. This allows the transmission to be operated as a conventional automatic unit by selecting P, R, N, or D on the selector lever. Movement of the selector lever across the gate to the 'M/S' position puts the transmission into electronic sport mode. Movement of the selector lever in a lateral position to the + or - positions puts the transmission into electronic manual 'Steptronic' mode.

OPERATION

Power Distribution
Feed from the positive battery terminal (C0192) is supplied to fuse 53 and fuse 54 of the passenger compartment fuse box (C0632) and the fuse holder (C1875) on R wires. The 100 A fuse located in the fuse holder (C1878) provides a constant battery feed to the Engine Control Module (ECM) relay (C1895) on an R wire. The 50 A fuse located in the fuse holder (C1876) provides a constant battery feed to the transfer box ECU (C1855) on a pair of R wires.

Fuse 54 of the passenger compartment fuse box (C0583) provides a constant battery feed to the EAT ECU (C0932) on a RY wire. Fuse 53 of the passenger compartment fuse box (C0583) provides a constant battery feed to the ignition switch (C0099) on an R wire. When the ignition switch is turned to the 'auxiliary' position, current flows across the switch (C0099) to fuse 37 of the passenger compartment fuse box (C0585) on a PB wire. Fuse 37 (C0587) provides an ignition feed to the transfer box ECU (C1319) on a PU wire.

When the ignition switch is turned to the 'ignition' position, current flows across the switch (C0099) to fuse 5, fuse 33, and fuse 35 of the passenger compartment fuse box (C0585) on a G wire. Fuse 5 (C0587) provides an ignition feed to the EAT ECU (C0932) on a GW wire. Fuse 33 (C0587) provides an ignition feed to the transfer box ECU (C1319) on a GP wire. Fuse 35 (C0587) provides an ignition feed to the Hill Descent Control (HDC) switch (C0365) on a GBY wire.

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.

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.

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.

Transmission Temperature Sensor
The temperature of the Automatic Transmission Fluid (ATF) is measured by the Negative Temperature Coefficient (NTC) transmission temperature sensor. The EAT ECU (C1835) provides a feed to the temperature sensor (C0244) on a BR wire. By measuring the voltage returned on a WR wire, the EAT ECU can determine ATF temperature.

Inhibitor Switch
The inhibitor switch is mounted on the LH side of the transmission, and enables the EAT ECU to monitor the position of the manual selector spool valve and the selected drive program. The EAT ECU (C1835) provides an ignition feed to the inhibitor switch (C0244) on a YB wire. When Park or Neutral is selected, the inhibitor switch (C0244) returns a feed back to the EAT ECU (C1835) on an O wire. When Drive is selected, the inhibitor switch (C0244) returns a feed back to the EAT ECU (C1835) on a B wire.

When shift solenoid A is energised, the inhibitor switch (C0244) returns a feed back to the EAT ECU (C1835) on a PW wire. When shift solenoid B is energised, the inhibitor switch (C0244) returns a feed back to the EAT ECU (C1835) on a YB wire. When shift solenoid C is energised, the inhibitor switch (C0244) returns a feed back to the EAT ECU (C1835) on a TB wire.

NOTE: Wire colour TB is transparent with a black tracer.

Shift Interlock Solenoid
To lock the selector lever assembly, the EAT ECU (C0193) provides a feed to the shift interlock solenoid (C0673) on a BP wire. An earth path is provided by the EAT ECU (C0193) on an NP wire.

Steptronic
When manual (Steptronic) mode is selected, the EAT ECU selects gears according to inputs received from the Steptronic switch. The EAT ECU (C0193) provides two feeds to the Steptronic switch (C1664); one on a UY wire, one on a US wire. If a downshift is requested via the selector lever, a momentary earth is created. Current on the UY wire is allowed to flow across the switch to earth on an NB wire. Sensing this, the EAT ECU downshifts 1 gear.

If an upshift is requested via the selector lever, a momentary earth is created. Current on the US wire is now allowed to flow across the switch to earth on an NB wire. Sensing this, the EAT ECU upshifts 1 gear.