Transmission Management

AJ16 - Transmission Management

Normally Aspirated 4.0 Litre Models
The transmission management system is revised to accommodate the introduction of the AJ16 engine, on-board diagnostics (OBD) II and, where fitted, traction control.

A transmission fluid temperature sensor is introduced to improve gear change quality at low fluid temperatures. Component changes consist of a new transmission internal harness, a new transmission mode switch and a new transmission control module (TCM). The TCM to engine management interface is revised to reduce the number of connections.

Transmission Internal Harness





The new internal harness has an integral thermistor probe to supply a fluid temperature signal to the TCM. To accommodate the temperature signal, the harness connector on the left side of the transmission is changed from an eight-way to a nine-way connector.

Transmission Mode Switch
As a result of the introduction of traction control,

Inputs and Outputs

Changes to the inputs and outputs of the TCM are as follows:
^ Two connections are added for the transmission fluid temperature sensor
^ Where traction control is installed, a traction control connection is added from the anti-lock braking system/traction control, electronic control module (ABS/TC CM)
^ One of the torque reduction signal connections is deleted
^ The pin code connections are deleted: PECUS programming is now implemented through the electronically erasable programmable read only memory (EEPROM)
^ The throttle position sensor connections are deleted: a new connection with the engine control module now supplies the throttle position signal
^ The first gear inhibit selection input and indicator output connections are deleted.

Transmission Control Module











The new TCM is a single board unit which is calibrated to match the AJ16 engine. The unit is programmed for specific market applications using the programmable electronic control unit system (PECUS). A 55-way connector on the TCM casing provides the interface with the vehicle wiring.

The TCM is installed on a two-part bracket assembly in the interior, on the passenger side of the upper toe-board. One part of the bracket attaches to the mounting studs of the anti-lock braking system modulator and the other to the TCM. A single securing nut locks the two parts together, enabling easy removal/installation.

The TCM uses the bulk fluid temperature signal to calculate gear change fluid pressure offsets, to optimise gear change quality at low temperatures.

On receipt of the traction control active signal, the TCM adopts a traction control shift pattern to assist in preventing wheelspin.

Fault codes are now stored in a non-volatile, electronically erasable programmable read-only memory (EEPROM), and can only be erased with a portable diagnostic unit (PDU) or scan tool (disconnecting the battery or the TCM connector no longer erases the fault codes). The numbering of the TCM fault codes is revised to conform to the requirements of the OBD II system (see Electric/Electronic - OBD II section). Additional fault codes are introduced for the bulk fluid temperature and traction control signals.

If the TCM detects a fault, it stores the fault code and activates the transmission malfunction indicator lamp (MIL). For faults detected in less critical inputs/outputs, the TCM substitutes the faulty input/output with a default value and continues the normal mode of operation. This allows the vehicle to be driven normally, although gear change quality will be affected to a greater or lesser degree.

For certain faults the TCM also disables the sport mode.

For more serious faults, the TCM may adopt a 'limp home' mode by disabling the shift and torque converter clutch solenoids. This allows the vehicle to be driven, but no gear changes will occur in the forward range. If the 'limp home' mode is adopted while the vehicle is in motion the transmission is kept in fourth gear. If the vehicle is then brought to a halt, neutral selected and drive re-selected, or if the 'limp home' mode is adopted while the vehicle is stationary, the transmission is kept in third gear. With the new TCM, activation of the transmission MIL during the start sequence is also revised. When the ignition switch is set to position II (ignition ON) the MIL comes on briefly and then goes off; when the ignition switch is set to position III (engine start) the MIL may flash briefly, but then remains off. A continuously flashing MIL indicates the data in the EEPROM is corrupted or the TCM is not PECUS programmed.