P0744

DTC P0744 A/T TCC SN FUNCTION (LOCK-UP)
Description
- This is an OBD-II self-diagnostic item and not available in TCM self-diagnosis.
- This malfunction will not be detected while the O/D OFF indicator lamp is indicating another self-diagnosis malfunction.
- This malfunction is detected when the A/T does not shift into fourth gear position or the torque converter clutch does not lock up as instructed by the TCM. This is not caused by electrical malfunction (circuits open or shorted) but by mechanical malfunction such as control valve sticking, improper solenoid valve operation, malfunctioning oil pump or torque converter clutch, etc.





CONSULT-II REFERENCE VALUE IN DATA MONITOR MODE
Remarks: Specification data are reference values.

ON BOARD DIAGNOSTIC LOGIC








This diagnosis monitors actual gear position by checking the torque converter slip ratio calculated by TCM as follows:
Torque converter slip ratio = A x C/B
A: Output shaft revolution signal from revolution sensor
B: Engine speed signal from ECM
C: Gear ratio determined as gear position, which TCM supposes
If the actual gear position is much lower than the position (4th) supposed by TCM, the slip ratio will be much less than normal. In case the ratio does not reach the specified value, TCM judges this diagnosis malfunction. This malfunction will be caused when shift solenoid valve B is stuck closed.

DIAGNOSTIC TROUBLE CODE (DTC) CONFIRMATION PROCEDURE

CAUTION: Always drive vehicle at a safe speed.

NOTE: If "DIAGNOSTIC TROUBLE CODE CONFIRMATION PROCEDURE" has been previously conducted, always turn ignition switch "OFF" and wait at least 5 seconds before conducting the next test.

After the repair, perform the following procedure to confirm the mal function is eliminated.

With CONSULT-II





1. Start engine and select "DATA MONITOR" mode for "A/T" with CONSULT-II.





2. Make sure that output voltage of A/T fluid temperature sensor is within the range below.
FLUID TEMP SEN: 0.4-1.5V
If out of range, drive the vehicle to decrease the voltage (warm up the fluid) or stop engine to increase the voltage (cool down the fluid).
3. Select "TCC SN FNCTN P0744" of "DTC WORK SUPPORT" mode for "A/T" with CONSULT-II and touch "START".





4. Accelerate vehicle to more than 80 km/h (50 MPH) and maintain the following condition continuously until "TESTING" has turned to "COMPLETE". (It will take approximately 30 seconds after "TESTING" shows.)
THROTTLE POSI: 1.0/8 - 2.0/8 (at all times during step 4)
Selector lever: D position (OD "ON")
TCC SN DUTY: More than 94%
VHCL/S SE.A/T: Constant speed of more than 80 km/h (50 MPH)
Check that "GEAR" shows "4".
If "TESTING" does not appear on CONSULT-II for a long time, select "SELF-DIAGNOSIS". In case a 1st trip DTC other than P0744 is shown, refer to applicable "TROUBLE DIAGNOSIS FOR DTC".
5. Make sure that "OK" is displayed. (If "NG" is displayed, refer to "Diagnostic Procedure" below. refer to "Diagnostic Procedure" below. Refer to "Shift Schedule" Mechanical Specifications

With GST
Follow the procedure "With CONSULT-II".








Wiring Diagram-AT-TCCSIG

Diagnostic Procedure
1. CHECK SHIFT UP (D3 TO D4)





During "Cruise Test- Part 1" , does A/T shift from D3 to D4 at the specified speed? Road Test
Yes or No
Yes >> GO TO 10.
No >>GO TO 2.

2. CHECK LINE PRESSURE





Perform line pressure test.
Refer to "Line Pressure Test" Line Pressure Test
OK or NG
OK >> GO TO 3.
NG >> GO TO 6.

3. CHECK CONTROL VALVE
1. Disassemble control valve assembly. Refer to "Disassembly" Service and Repair





2. Check to ensure that:
- Valve, sleeve and plug slide along valve bore under their own weight.
- Valve, sleeve and plug are free from burrs, dents and scratches.
- Control valve springs are free from damage, deformation and fatigue.
- Hydraulic line is free from obstacles.
OK or NG
OK >>GO TO 4.
NG >> Repair control valve.

4. CHECK SHIFT UP (D3 TO D4)
Does A/T shift from D2 to D1 at the specified speed? Yes or No
Yes >> GO TO 5.
No >> Check control valve again. Repair or replace control valve assembly.

5. CHECK DTC
Perform "DIAGNOSTIC TROUBLE CODE (DTC) CONFIRMATION PROCEDURE".
OK or NG
OK >> INSPECTION END NG >> GO TO 10. Check lock-up condition.

6. CHECK LINE PRESSURE SOLENOID VALVE
1. Remove control valve assembly.
Refer to "REMOVAL" Service and Repair





2. Check line pressure solenoid valve operation.
Refer to "Component Inspection".
OK or NG
OK >> GO TO 7.
NG >> Replace solenoid valve assembly.

7. CHECK CONTROL VALVE
1. Disassemble control valve assembly.
Refer to "Disassembly" Service and Repair





2. Check line pressure circuit valves for sticking.
- Pressure regulator valve
- Pilot valve
- Pressure modifier valve
OK or NG
OK >> GO TO 8.
NG >> Repair control valve.

8. CHECK SHIFT UP (D3 TO D4)
Does A/T shift from D3 to D4 at the specified speed?
Yes or No
Yes >> GO TO 9.
No >> Check control valve again. Repair or replace control valve assembly.

9. CHECK DTC
Perform "DIAGNOSTIC TROUBLE CODE (DTC) CONFIRMATION PROCEDURE".
OK or NG
OK >> INSPECTION END
NG >> GO TO 10. Check for proper lock-up.

10. CHECK LOCK-UP CONDITION





During "Cruise Test - Part 1" ("Cruise Test-Part 1"), does A/T perform lock-up at the specified speed?
Yes or No
Yes >> Perform "Cruise Test - Part 1" again and return to the start point of this test group.
No >> GO TO 11.

11. CHECK TORQUE CONVERTER CLUTCH SOLENOID VALVE
1. Remove control valve assembly. Refer to "REMOVAL" Service and Repair





2. Check torque converter clutch solenoid valve operation. Refer to "TORQUE CONVERTER CLUTCH SOLENOID VALVE"
OK or NG
OK >> GO TO 12.
NG >> Replace solenoid valve assembly.

12. CHECK CONTROL VALVE
1. Disassemble control valve assembly.
Refer to "Disassembly" Service and Repair





2. Check control valves for sticking.
- Torque converter clutch control valve
- Torque converter clutch relief valve
OK or NG
OK >> GO TO 13.
NG >> Repair control valve.

13. CHECK LOCK-UP CONDITION
Does A/T perform lock-up at the specified speed?
Yes or No
Yes >> GO TO 14.
No >> Check control valve again. Repair or replace control valve assembly.

14. CHECK DTC
Perform "DIAGNOSTIC TROUBLE CODE (DTC) CONFIRMATION PROCEDURE".
OK or NG
OK >> INSPECTION END
NG >> Perform "Cruise Test-Part 1" again and return to the start point of this test group.

Component Inspection
SOLENOID VALVES
- Refer to "REMOVAL" Service and Repair

Resistance Check








- Check resistance between two terminals.

Operation Check





- Check solenoid valve by listening for its operating sound while applying battery voltage to the terminal and ground.