P0744

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






TCM TERMINALS AND REFERENCE VALUE
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 malfunction is eliminated.



With Generic Scan Tool
(1) Start engine and warm up ATF.
(2) Start vehicle with selector lever in "D" position, throttle opening 1/8 - 2/8 and D4 lock-up position for approximately 30 seconds. Check that vehicle runs through gear shift of D1 -> D2 -> D3 -> D4 -> D4 lock-up, in accordance with shift schedule. Refer to shift schedule.
(3) Select "MODE 7" with GST.













DIAGNOSTIC PROCEDURE



COMPONENT INSPECTION
Solenoid valves









Resistance check
Check resistance between terminals ((2), (1), (3), (4) or (5)) and ground.






Operation check
Check solenoid valve by listening for its operating sound while applying battery voltage to the terminals ((2), (1), (3), (4) or (5)) and ground.