Part 4
4.2L V8 SUPERCHARGED 6HP26 AUTOMATIC TRANSMISSION (PART 4)GEAR SELECTOR LEVER ASSEMBLY
GEAR SELECTOR LEVER ASSEMBLY (PART 1):
GEAR SELECTOR LEVER ASSEMBLY (PART 2):
The gear selector lever assembly is located in a central position on the transmission tunnel, between the front driver and passenger seats. A mounting plate is secured to the transmission tunnel and provides the mounting for the selector lever assembly.
The selector lever comprises a cast mounting plate which provides for the location of the selector components. The lever is connected to a gimbal mechanism which allows for the selection of P, R, N, D in a forward or backward direction and selection between automatic and manual/sport in a left/right transverse direction. When manual/sport mode is selected, the lever can be moved in a forward or backward direction to select + or - for manual (CommandShift) operation.
When the selector lever is moved to the M/S position, the Bowden cable to the transmission is mechanically disconnected at the shifter. If left in Sport mode all gear changes are performed automatically. If Manual (CommandShift) mode is selected, all gear changes are based on switched ground inputs received by the TCM from the Manual +/- CommandShift switch.
The selector mechanism houses these components:
^ Manual +/- CommandShift switch
^ Shift interlock solenoid
^ High/Low range selector switch
^ Hill Descent Control (HDC) switch
^ Selector position LED display
^ Selector lever position switch
^ Manual/Sport switch
^ Key interlock mechanism.
There are four selector lever positions and two additional positions for manual/sport operation:
^ P (Park) - Prevents the vehicle from moving by locking the transmission
^ R (Reverse) - Select only when the vehicle is stationary and the engine is at idle - selects reverse direction
^ N (Neutral) - No torque transmitted to drive wheels
^ D (Drive) - This position uses all six forward gears in high and low ranges
^ M/S (Sport mode) - This position uses all six forward gears as in 'D', but will upshift at higher engine speeds improving acceleration
^ + and - ('CommandShift' mode) - Movement of the selector lever in the +/- positions, when the lever is in the M/S position, will operate the transmission in manual (CommandShift) mode, allowing the driver to manually select all six forward gears. The selector lever position is displayed to the driver on the selector position LED display and in the instrument cluster. In 'CommandShift' mode, if a gear is selected, but the TCM logic prevents selection of that gear, the requested gear is initially displayed. The TCM will engage the next allowed gear and then display that gear.
^ The selector lever position is displayed to the driver on the selector position LED display and in the instrument cluster. In 'CommandShift' mode, if a gear is selected, but the TCM logic prevents selection of that gear, the requested gear is initially displayed. The TCM will engage the next allowed gear and then display that gear.
Manual +/- CommandShift Switch
The manual +/- switch is located on the left hand side of the selector lever assembly. The switch comprises a housing which provides the location for a sliding contact. When the selector lever is moved to the manual/sport position, a dog on the lever engages with a slotted abutment on the switch sliding contact. When the lever is moved to the + or - position the dog moves the switch completing a momentary earth circuit with one of two microswitches at each end of the switch which correspond to the + or - positions.
This momentary signal is received by the TCM which, on first operation of the switch, initiates manual mode and operates the transmission in the selected gear.
In this position, a spring will move the selector lever to the center position when released.
Shift Interlock Solenoid
The shift interlock solenoid is located at the front of the selector lever assembly. The selector lever is connected to a locking plate which has two holes which correspond to the 'P' and 'N' positions. When the ignition is on or the engine is running, the solenoid is energized by the TCM when the selector lever is in the 'P' or 'N' positions. When energized, the solenoid ejects a pin which engages in the locking plate preventing the lever from being moved.
When the foot brake is applied, a signal from a brake switch is passed to the TCM which de-energizes the solenoid allowing the lever to be moved from the 'P' or 'N' position. This prevents the selector from being moved to the 'D' or 'R' position unintentionally and the application of the brakes also prevents the vehicle 'creeping' when the gear is engaged.
High/Low Range Selector Switch
The high/low range switch is located on the selector lever cover, on the right hand side of the selector lever. The switch can be identified by the a high/low range legend graphic and the switch lever is colored white. High or low range can be selected using this switch providing the vehicle speed is within defined limits and the gear selector lever is in the neutral position.
Hill Descent Control (HDC) Switch
The HDC switch is located on the selector lever cover, on the left hand side of the selector lever. The switch can be identified by the HDC legend graphic and the switch lever is colored yellow. Operation of the HDC switch is not directly related to automatic transmission operation.
Selector Position LED Display
The selector position LED display is located on the selector lever cover, between the HDC and high/low range switches. The display has a graphic which shows the lever positions P, R, N, D, M/S and +/-. The P, R, N, D and M/S positions each have a small, red LED which illuminates when that position is selected. The +/- positions do not have an LED.
The LED display is controlled by the selector lever position switch, with the two components connected via a five wire ribbon cable. The LED display is powered from the Generic Electronic Module (GEM) and remains illuminated until the GEM is in sleep mode. The LED display is active at all times when the ignition is on.
Selector Lever Position Switch
The selector lever position switch is located on the right hand side of the selector lever assembly. The switch has a moving contact which is connected to the selector lever. As the lever is moved, the sliding contact moves in the switch completing a circuit with four further contacts in the switch which represent the four lever positions; P, R, N and D. The switch is connected to the selector position LED display via a ribbon cable and provides the power for the display LEDs. The switch receives its power supply from the GEM.
Manual/Sport Switch
The manual/sport switch is located at the rear of the selector lever assembly. The manual/sport switch is a cam operated microswitch. A lever with a roller is attached to the switch body. When the selector lever is moved from the automatic 'D' position to the manual/sport 'M/S' position, the roller contacts a cam on the selector lever which depresses the switch lever and operates the switch. The switch contacts remain closed when the selector lever is in the manual/sport position.
The operation of the switch completes an earth path which is sensed by the TCM which switches the transmission operation to sport when M/S is selected and deselects sport mode when D (automatic operation) is reselected. The completed earth path is connected to the TCM via the M/S LED on the selector lever display which is illuminated by an output from the TCM when M/S is selected.
Selector Cable
The selector cable is a Bowden type cable that connects the selector lever to the manual selector spool valve. A 'C' clip secures the outer cable to the selector lever assembly. The inner cable is secured to an arm which is connected to the selector lever via a 'U' shaped bracket and pin.
The transmission end of the outer cable is secured to a bracket on the transmission by a clamp nut. The transmission has an operating lever which is attached to and operates the manual selector control spool valve. The inner cable is attached to the operating lever by a clamp bush and locknut. The clamp bush allows for the adjustment of the selector cable.
Key Interlock Mechanism
Key Interlock Mechanism (Part 1):
Key Interlock Mechanism (Part 2):
The key interlock mechanism prevents the key from being removed from the ignition switch when the selector lever is any position other than 'P' PARK. This prevents the vehicle being accidentally left in neutral which would cause the vehicle to move if hand brake was not applied.
The mechanical mechanism is operated by a Bowden cable which is attached between the selector lever assembly and the ignition switch. When the ignition switch is turned to the on position, the switch rotates a lever which in turn pulls the cable. This lifts a latch in the selector lever assembly which is engaged with the selector lever when in the 'P' position.
INSTRUMENT CLUSTER
INSTRUMENT CLUSTER (PART 1):
The instrument cluster is connected to the TCM via the CAN. Transmission status is transmitted by the TCM and displayed to the driver on one of two displays in the instrument cluster.
Malfunction Indicator Lamp (MIL)
The MIL is located in the lower left hand corner of the instrument cluster, below the fuel gage. Transmission related faults which may affect the vehicle emissions output will illuminate the MIL.
The MIL is illuminated by the ECM on receipt of a relevant fault message from the TCM on the CAN. The nature of the fault can be diagnosed using T4 which reads fault codes stored in the TCM memory.
Transmission Status Display
The transmission status display is located on the right hand side of the message center. The display shows the selector lever position and in the case of manual (CommandShift) mode, the selected gear.
INSTRUMENT CLUSTER (PART 2):
Message Center Display
The message center is located below the speedometer and the tachometer at the bottom of the instrument cluster. The message center is a Liquid Crystal Display (LCD) to relay vehicle status information to the driver.
TRANSMISSION CONTROL MODULE (TCM)
The TCM is an integral part of the Mechatronic valve block which is located at the bottom of the transmission, within the fluid pan. The TCM is the main controlling component of the transmission.
The TCM processes signals from the transmission speed and temperature sensors, engine control module and other vehicle systems. From the received signal inputs and pre-programmed data, the module calculates the correct gear, torque converter clutch setting and optimum pressure settings for gear shift and lock-up clutch control.
The TCM outputs signals to control the shift control solenoid valve and the Electronic Pressure Regulator Solenoids (EPRS) to control the hydraulic operation of the transmission.
The ECM supplies the engine management data on the high speed CAN bus system. The TCM requires engine data to efficiently control the transmission operation, for example; flywheel torque, engine speed, accelerator pedal angle, engine temperature etc.
The steering angle sensor and the ABS module also supply data to the TCM on the high speed CAN bus system. The TCM uses data from these systems to suspend gear changes when the vehicle is cornering and/or the ABS module is controlling braking or traction control.
The selector lever is connected to the automatic transmission and the position switch in the transmission by a Bowden cable. Movement of the selector lever moves the position switch via the Bowden cable and the switch position informs the TCM of the selected position. The sport/manual +/- CommandShift switch passes manual/sport selections to the TCM. An additional switch provides a selector lever in park position signal. Once the selector lever position is confirmed, the TCM outputs appropriate information which is received by the instrument cluster to display the gear selection information in the message center.
The Mechatronic valve block also contains the speed and temperature sensors. These are integral with the Mechatronic valve block and cannot be serviced individually. The speed sensors measure the transmission input and output speeds and pass signals to the TCM. The fluid temperature sensor is also located in the valve block and measures the fluid temperature of the transmission fluid in the fluid pan.
The TCM is connected to the starter relay coil. When the selector lever is in PARK or NEUTRAL, the module provides a ground for the coil allowing the starter relay to be energized and allow starter motor operation. If the selector lever is in any other position, the module will not provide the ground preventing starter motor operation.
Inputs and Outputs
Connector C0193
Connector C0193 (Part 1):
This table shows the connector pin details for the connector on the transmission.
Connector C0193 (Part 2):
DIAGNOSTICS
The diagnostic socket is located in the instrument panel, in the driver's side stowage tray. The socket is secured in the instrument panel and protected by a hinged cover.
Diagnostic Socket
Diagnostic Socket (Part 1):
Diagnostic Socket (Part 2):
The diagnostic socket allows the exchange of information between the various modules on the bus systems and T4 or a generic scan tool. The information is communicated to the socket via the high speed CAN bus from the TCM. This allows the retrieval of diagnostic information and programming of certain functions using T4 or a suitable diagnostic tool.
The TCM uses a P code strategy which stores industry standard Diagnostic Trouble Codes (DTC) relating to faults.
P012100-P074000:
P074100-P275900:
P276100-P276400:
CONTROLLER AREA NETWORK (CAN)
The high speed CAN broadcast bus network is used to connect the powertrain modules. The CAN bus is connected between these electronic units:
High Speed CAN Bus
^ TCM
^ Instrument cluster
^ Air suspension control module
^ Steering angle sensor
^ Center console switch pack
^ Restraints control module
^ Engine Control Module (ECM)
^ ABS module
^ Adaptive front lighting control module
^ Transfer box control module
^ Diagnostic socket.
The CAN bus allows a fast exchange of data between modules. The CAN bus comprises two wires which are identified as CAN high (H) and CAN low (L). The two wires are colored yellow/black (H) and yellow/brown (L) and are twisted together to minimize electromagnetic interference (noise) produced by the CAN bus messages.
In the event of CAN bus failure, these symptoms may be observed:
^ Transmission operates in default mode
^ Torque converter lock-up clutch control is disabled
^ Gear position indication in instrument cluster message center inoperative (this will also occur with any transmission fault).