P0744
DTC P0744 A/T TCC S/V 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
On Board Diagnosis 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.
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 is detected.
Diagnostic trouble code A/T TCC S/V FNCTN with CONSULT-II or P0744 without CONSULT-II is detected when A/T cannot perform lock-up even if electrical circuit is good.
Possible Cause
Check the following items.
- Line pressure solenoid valve
- Torque converter clutch solenoid valve
- Each clutch
- Hydraulic control circuit
Diagnostic Trouble Code (DTC) Confirmation Procedure
CAUTION: Always drive vehicle at a safe speed.
NOTE: If DTC Confirmation Procedure has been previously conducted, always turn ignition switch OFF and wait at least 10 seconds before conducting the next test.
After the repair, perform the following procedure to confirm the malfunction 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 - 1.5 V
If out of range, drive vehicle to decrease voltage (warm up the fluid) or stop engine to increase voltage (cool down the fluid).
3. Select TCC S/V FNCTN P0744 of DTC WORK SUPPORT mode for A/T with CONSULT-II and touch START.
4. Accelerate vehicle to more than 70 km/h (43 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 (O/D ON)
TCC S/V DUTY: More than 94%
VHCL/S SE.A/T: Constant speed of more than 70 km/h (43 MPH)
- Check that GEAR shows 4.
- For shift schedule, refer to Shift Schedule.
If TESTING does not appear on CONSULT-II for a long time, select SELF-DIAG RESULTS. In case a 1st trip DTC other than P0744 is shown, refer to applicable TROUBLE DIAGNOSIS FOR ATF.
5. Make sure that OK is displayed. (If NG, is displayed, refer to DIAGNOSTIC PROCEDURE.) Refer to Diagnostic Procedure. Refer to Shift Schedule.
WITH GST
Follow the procedure With CONSULT-II.
Wiring Diagram-AT-TCCSIG
AT-TCCSIG-01:
AT-TCCSIG-01
TCM TERMINAL AND REFERENCE VALUE MEASURED BETWEEN EACH TERMINAL AND 25 OR 48 (TCM GROUND)
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?
Yes or No
Yes >> GO TO 11.
No >> GO TO 2.
2. CHECK LINE PRESSURE
Perform line pressure test.
Refer to AT-453, 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.
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 D3 to D4 at the specified speed?
Yes or No
Yes >> GO TO 5.
No >> Check transaxle internal components (clutch, brake, etc.).
5. CHECK DTC
Perform AT-535, Diagnostic Trouble Code (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.
- Line pressure solenoid valve
2. Check resistance to the terminal and ground.
OK or NG
OK >> GO TO 8.
NG >> Replace solenoid valve assembly.
7. CHECK VALVE OPERATION
1. Remove control valve assembly.
- Line pressure solenoid valve
2. Check solenoid valve by listening for its operating sound while applying battery voltage and ground to the solenoid.
OK or NG
OK >> GO TO 8.
NG >> Replace solenoid valve assembly.
8. CHECK CONTROL VALVE
1. Disassemble control valve assembly. Refer to DISASSEMBLY.
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)
Does A/T shift from D3 to D4 at the specified speed?
Yes or No
Yes >> GO TO 10.
No >> Check transaxle internal components (clutch, brake, etc.)
10. CHECK DTC
Perform AT-535, Diagnostic Trouble Code (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, 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 12.
12. CHECK VALVE RESISTANCE
1. Remove control valve assembly.
- Torque converter clutch solenoid valve
2. Check resistance between terminal cord assembly connector F30 terminal 5 and ground.
OK or NG
OK >> GO TO 14.
NG >> Replace solenoid valve assembly.
13. CHECK VALVE OPERATION
1. Remove control valve assembly.
- Torque converter clutch solenoid valve
2. Check solenoid valve by listening for its operating sound while applying battery voltage and ground to the solenoid.
OK or NG
OK >> GO TO 14.
NG >> Replace solenoid valve assembly.
14. CHECK CONTROL VALVE
1. Disassemble control valve assembly. Refer to DISASSEMBLY.
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
Does A/T perform lock-up at the specified speed?
Yes or No
Yes >> GO TO 16.
No >> Check transaxle internal components (clutch, brake, etc.).
16. CHECK DTC
Perform AT-535, 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.