Torque Converter Housing
The torque converter housing attaches the automatic transmission to the engine and contains the torque converter. The torque converter is connected to the engine drive plate and transmits the drive from the engine to the automatic transmission input shaft. When engaged, a hydraulic lock-up clutch in the torque converter prevents slippage, to give a direct drive from the engine to the automatic transmission for improved driving response.
COMPENSATION FOR REDUCED ENGINE TORQUE
In a similar way to the Towing mode, if the vehicle is producing less torque than would normally be the case (high altitude or very hot ambient air), the transmission will hold onto gears longer than would normally be the case. This is a very similar situation to towing, but the performance of the vehicle is reduced due to a lack of engine power, rather than the weight of the vehicle.
TORQUE CONVERTER LOCK-UP
Incorporated into the design of the automatic transmission system is a lock-up torque converter feature, where the Electronic Automatic Transmission Electronic Control Unit (EAT ECU) will activate the torque converter lock-up solenoid. When activated, the torque converter lock-up clutch will be engaged and no slip will be allowed. Direct drive through the torque converter will be provided in this condition.
The torque converter can be locked and unlocked during driving to improve driveability, fuel consumption and gear changing. The torque converter will not be locked until the transmission has calculated that the oil temperature has reached a predetermined temperature. This is calculated from the engine coolant temperature via a software timer within the EAT ECU. The length of this timer depends on several variables, including the engine coolant temperature during cranking, but is approximately as follows. With engine coolant temperature at about 77 F° (25 C°) the transmission does not take any time to warm up. With engine coolant temperature at 32 F° (0 C°) it takes the transmission fluid 7 minutes to warm up. With engine coolant temperature at about -13 F° (-25 C°) it takes the transmission fluid 12 minutes to warm up.
To enhance off road control, particularly when maneuvering at low speeds, torque converter lock-up does not occur when there is any degree of throttle opening. But when the throttle is closed above a preset engine speed, the lock-up clutch engages to provide maximum engine braking by locking the torque converter in any gear at zero percent throttle. This improves engine braking while negotiating steep gradients. This feature will be active only while there is no danger of stalling the engine.
TORQUE CONVERTER ROAD TEST
Note. A torque converter with a seized stator will be indicated by vehicle exhibiting good off line performance but sluggishness at higher speeds and excessive fuel consumption.
- Torque converter lockup can occur in either 3rd or 4th gear at speeds between 30-45 MPH (48-72 kph) and is dependent on load. A quick check of lockup can be made while driving at a steady speed in either 3rd or 4th gear.
- Slowly accelerate vehicle to speed greater than 30 MPH (48 kph). Press down accelerator briefly and observe tachometer. If tachometer moves 300-500 RPM but speed remains constant Direct Drive Clutch (DDC) did not engage and torque converter did not lockup. If tachometer does not move, DDC engages and torque converter locks up.
Torque Converter Clutch Solenoid Monitoring
For torque converter clutch solenoid monitoring information (Scheme 1)
Note. This monitor covers information for DTC P0722, P0741 and P0743.
Scheme 1
FAULT CODE 05: TORQUE CONVERTER LOCK-UP CLUTCH MONITORING/TORQUE CONVERTER LOCK-UP CLUTCH FAULT
Note. For circuit reference, see WIRING DIAGRAMS .
This fault code may affect driveability.
For fault code description and diagnostic test procedure (Scheme 2)- (Scheme 4). Freeze frame variables are N-MOT, VGT-$X and MMM. See TEST PROCEDURE under SELF-DIAGNOSTIC SYSTEM.
Scheme 2
Scheme 3
Scheme 4
FAULT CODE 22: STALL SPEED MONITORING/TORQUE CONVERTER SLIPPING
Note. For circuit reference, see WIRING DIAGRAMS .
This fault code will cause transmission to maintain current gear in low range, limp home mode in high range. It will also cause a shift in pressure to maximum, harsh gear shifts and engagement.
For fault code description and diagnostic test procedure (Scheme 5)- (Scheme 7). Freeze frame variables are N-MOT, VGT-$X and MMM. See TEST PROCEDURE under SELF-DIAGNOSTIC SYSTEM.
Scheme 5
Scheme 6
Scheme 7
FAULT CODE 25: SOLENOID VALVE FOR TC (SHORT CIRCUIT TO GROUND, OR OPEN CIRCUIT)/TORQUE CONVERTER LOCK-UP SOLENOID (MV3) OPEN CIRCUIT
Note. For circuit reference, see WIRING DIAGRAMS .
This fault code will cause the transmission to switch to limp home mode in low and high ranges. It will also cause a shift in pressure to maximum, and harsh gear shifts and engagement.
For fault code description and diagnostic test procedure (Scheme 8)and (Scheme 9). Carry out test as for fault code 28 but substitute terminal No. 32 in place of terminal No. 5. Freeze frame variables are N-MOT, AN8 and UBATT. See TEST PROCEDURE under SELF-DIAGNOSTIC SYSTEM.
Scheme 8
Scheme 9
FAULT CODE 33: CAN MESSAGE MD-IND INVALID, INDICATED BY F-TL-MES/CAN MESSAGE: ENGINE TORQUE INVALID
Note. For circuit reference, see WIRING DIAGRAMS .
This fault code will cause a substitution of engine torque that will be derived from other inputs. It may also affect shift quality.
For fault code description and diagnostic test procedure (Scheme 10)and (Scheme 11). Freeze frame variables are N-MOT, VGT-$X and MMM. See TEST PROCEDURE under SELF-DIAGNOSTIC SYSTEM.
Scheme 10
Scheme 11
FAULT CODE 34: CAN MESSAGE MD-IND INVALID (FFH)/CAN MESSAGE: ENGINE TORQUE INVALID
Note. For circuit reference, see WIRING DIAGRAMS .
This fault code will cause a substitution of engine torque that will be derived from other inputs. It may also affect shift quality.
For fault code description and diagnostic test procedure (Scheme 12)and (Scheme 13). Freeze frame variables are N-MOT, VGT-$X and MMM. See TEST PROCEDURE under SELF-DIAGNOSTIC SYSTEM.
