P0734

DTC P0734 A/T 4TH GEAR FUNCTION





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 "P0734 A/T 4TH GR FNCTN" with CONSULT-III is detected when A/T cannot be shifted to the 4th gear position 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 A is stuck open or 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 A stuck open: 2, 2, 3 and 3* positions
In case of gear position with shift solenoid valve B stuck closed: 1, 2, 2 and 1* positions to each gear position above
*: "P0734 A/T 4TH GR FNCTN" is detected.




Possible Cause
- Shift solenoid valve A
- Shift solenoid valve B
- Line pressure 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 the vehicle to decrease the voltage (warm up the fluid) or stop engine to increase the voltage (cool down the fluid).
4. Select "4TH GR FNCTN P0734" of "DTC and SRT CONFIRMATION" mode for "TRANSMISSION" with CONSULT-III and touch "START".
5. Accelerate vehicle to 55 to 65 km/h (34 to 40 MPH) under the following conditions and release the accelerator pedal completely.
THROTTLE POSI: Less than 5.5/8 (at all times during step 4)
SLCT LVR POSI: "D" position
- Make sure that "GEAR" shows "3" after releasing pedal.
6. Depress accelerator pedal steadily with 1.0/8 - 2.0/8 of "THROTTLE POSI" from a speed of 55 to 65 km/h (34 to 40 MPH) until "TESTING" has turned to "STOP VEHICLE" or "COMPLETED". (It will take approximately 3 seconds.)
If the check result NG appears on CONSULT-III screen, go to "Diagnosis Procedure".
If "STOP VEHICLE" appears on CONSULT-III screen, go to following step.
- Make sure that "GEAR" shows "4" when depressing accelerator pedal with 1.0/8 - 2.0/8 of "THROTTLE POSI".
- If "TESTING" does not appear on CONSULT-III for a long time, select "SELF-DIAG RESULTS" for "TRANSMISSION". In case a DTC other than "P0734 A/T 4TH GR FNCTN" is shown, refer to CONSULT-III Function (A/T).
7. Stop vehicle.
8. Follow the instruction displayed. (Check for normal shifting referring to the table below.)





9. Make sure that "OK" is displayed. (If "NG" is displayed, refer to "Diagnostic Procedure".)
Refer to "Diagnosis Procedure".
Refer to Vehicle Speed At Which Gear Shifting Occurs.

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 7.
3.CHECK VALVE RESISTANCE
1. Remove control valve assembly. Refer to Service and Repair.
- Shift solenoid valve A
- Shift solenoid valve B
2. Check resistance between terminal cord assembly harness connector terminals and ground. Refer to and P0755.





OK or NG
OK >> GO TO 4.
NG >> Replace solenoid valve assembly.





4.CHECK VALVE OPERATION
1. Remove control valve assembly. Refer to Service and Repair.
- Shift solenoid valve A
- Shift solenoid valve B
2. Check solenoid valve by listening for its operating sound while applying battery voltage to the terminals and ground. Refer to P0750 and P0755.
OK or NG
OK >> GO TO 5.
NG >> Replace solenoid valve assembly.





5.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 6.
NG >> Repair control valve.
6.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 >> Check control valve again. Repair or replace control valve assembly.
7.CHECK VALVE RESISTANCE
1. Remove control valve assembly. Refer to Service and Repair.
- Line pressure solenoid valves
2. Check resistance between terminal cord assembly harness connector terminal and ground. Refer to .










OK or NG
OK >> GO TO 8.
NG >> Replace solenoid valve assembly.
8.CHECK VALVE OPERATION
1. Remove control valve assembly. Refer to Service and Repair.
- Line pressure solenoid valves
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 9.
NG >> Replace solenoid valve assembly.
9.CHECK CONTROL VALVE
1. Disassemble control valve assembly. Refer to Control Valve Assembly.
2. Check line pressure circuit valves for sticking.
- Pilot valve
- Shift solenoid valve A
- Shift solenoid valve B
OK or NG
OK >> GO TO 10.
NG >> Repair control valve.
10.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 >> Check control valve again. Repair or replace control valve assembly.
11.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.