Automatic Transmission

DTC P0744 A/T TCC S/V FUNCTION (LOCK-UP)





Description
- This malfunction will not be detected while the OD 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-III Reference Value in Data Monitor Mode









On Board Diagnosis Logic
- This is an OBD-II self-diagnostic item.
- Diagnostic trouble code "P0744 A/T TCC S/V FNCTN" with CONSULT-III is detected when A/T cannot perform lock-up even if electrical circuit is good.
- 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.
- Gear positions supposed by TCM are as follows.
In case of gear position with no malfunctions: 1, 2, 3 and 4 positions
In case of gear position with shift solenoid valve B stuck closed: 1, 2, 2 and 1* positions to each gear position above
*: "P0744 A/T TCC S/V FNCTN" is detected.




Possible Cause
- Line pressure solenoid valve
- Torque converter clutch solenoid valve
- Each clutch
- Hydraulic control circuit




DTC Confirmation Procedure

CAUTION:
- Always drive vehicle at a safe speed.
- If performing this "DTC Confirmation Procedure" again, always turn ignition switch OFF and wait at least 10 seconds before continuing.
After the repair, perform the following procedure to confirm the malfunction is eliminated.

WITH CONSULT-III
1. Start engine and select "DATA MONITOR" mode for "TRANSMISSION" with CONSULT-III.
2. Touch "START".
3. Make sure that output voltage of A/T fluid temperature sensor is within the range below.
FLUID TEMP SE: 0.4 - 1.5 V
If out of range, drive vehicle to decrease voltage (warm up the fluid) or stop engine to increase voltage
(cool down the fluid).
4. Select "TCC S/V FNCTN P0744" of "DTC and SRT CONFIRMATION" mode for "TRANSMISSION" with CONSULT-III and touch "START".
5. Accelerate vehicle to more than 80 km/h (50 MPH) and maintain the following conditions 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)
SLCT LVR POSI: "D" position
TCC S/V DUTY: More than 94%
VEHICLE SPEED: Constant speed of more than 80 km/h (50 MPH)
- Make sure that "GEAR" shows "4".
- For shift schedule, refer to Vehicle Speed At Which Gear Shifting Occurs.
- If "TESTING" does not appear on CONSULT-III for a long time, select "SELF-DIAG RESULTS". In case a DTC other than "P0744 A/T TCC S/V FNCTN" is shown, refer to CONSULT-III Function (A/T).
6. Make sure that "OK" is displayed. (If "NG" is displayed, refer to "DIAGNOSTIC PROCEDURE".)
Refer to "Diagnosis Procedure".
Refer to Vehicle Speed At Which Lock-Up Occurs/Releases.

WITH GST
Follow the procedure "WITH CONSULT-III".




Diagnosis 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?
YES >> GO TO 11.
NO >> GO TO 2.
2.CHECK LINE PRESSURE
Perform line pressure test. Refer to Inspections Before Trouble Diagnosis.
OK or NG
OK >> GO TO 3.
NG >> GO TO 6.
3.CHECK CONTROL VALVE
1. Disassemble control valve assembly. Refer to Control Valve Assembly.
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)





During Cruise Test - Part 1.
Does A/T shift from D3 to D4 at the specified speed?
YES >> GO TO 5.
NO >> Check control valve again. Repair or replace control valve assembly.
5.CHECK DTC
Perform "DTC Confirmation Procedure".
OK or NG
OK >> INSPECTION END
NG >> GO TO 11. Check for proper lock-up.
6.CHECK VALVE RESISTANCE
1. Remove control valve assembly. Refer to Service and Repair.
- Line pressure solenoid valve
2. Check resistance between terminal cord assembly harness connector terminal and ground. Refer to .










OK or NG
OK >> GO TO 7.
NG >> Replace solenoid valve assembly.
7.CHECK VALVE OPERATION
1. Remove control valve assembly. Refer to Service and Repair.
- Line pressure solenoid valve
2. Check solenoid valve by listening for its operating sound while applying battery voltage to the terminal and ground. Refer to "Wiring Diagram - AT - LPSV".





OK or NG
OK >> GO TO 8.
NG >> Replace solenoid valve assembly.
8.CHECK CONTROL VALVE
1. Disassemble control valve assembly. Refer to Control Valve Assembly.
2. Check line pressure circuit valves for sticking.
- Pressure regulator valve
- Pilot valve
- Pressure modifier valve
OK or NG
OK >> GO TO 9.
NG >> Repair control valve.
9.CHECK SHIFT-UP (D3 TO D4)





During Cruise Test - Part 1.
Does A/T shift from D3 to D4 at the specified speed?
YES >> GO TO 10.
NO >> Check control valve again. Repair or replace control valve assembly.
10.CHECK DTC
Perform "DTC Confirmation Procedure".
OK or NG
OK >> INSPECTION END
NG >> GO TO 11. Check for proper lock-up.
11.CHECK LOCK-UP





During Cruise Test - Part 1.
A/T perform lock-up at the specified speed?
YES >> Perform "Cruise test -- Part 1" again and return to the start point of this test group.
NO >> GO TO 12.
12.CHECK VALVE RESISTANCE
1. Remove control valve assembly. Refer to Service and Repair.
- Torque converter clutch solenoid valve
2. Check resistance between terminal cord assembly harness connector terminal and ground. Refer to .










OK or NG
OK >> GO TO 13.
NG >> Replace solenoid valve assembly.
13.CHECK VALVE OPERATION
1. Remove control valve assembly. Refer to Service and Repair.
- Torque converter clutch solenoid valve
2. Check solenoid valve by listening for its operating sound while applying battery voltage to the terminal and ground. Refer to Automatic Transmission.





OK or NG
OK >> GO TO 14.
NG >> Replace solenoid valve assembly.
14.CHECK CONTROL VALVE
1. Disassemble control valve assembly. Refer to Control Valve Assembly.
2. Check control valves for sticking.
- Torque converter clutch control valve
- Torque converter clutch relief valve
OK or NG
OK >> GO TO 15.
NG >> Repair control valve.
15.CHECK LOCK-UP





During Cruise Test - Part 1.
A/T perform lock-up at the specified speed?
YES >> GO TO 16.
NO >> Check control valve again. Repair or replace control valve assembly.
16.CHECK DTC
Perform "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.