P0731
DTC P0731 A/T 1ST GEAR FUNCTIONDescription
- 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 first gear position 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. etc.
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 higher than the position (1st) supposed by TCM, the slip ratio will be more than normal. In case the ratio exceeds the specified value, TCM judges this diagnosis malfunction.
This malfunction will be caused when either shift solenoid valve A is stuck open or shift solenoid valve B is stuck open.
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 open: 4*, 3, 3 and 4 positions to each gear position above
*: P0731 is detected.
Diagnostic trouble code A/T 1ST GR FNCTN with CONSULT-II or P0731 without CONSULT-II is detected when A/T cannot be shifted to the 1st gear position even if electrical circuit is good.
Possible Cause
Check the following items.
- Shift solenoid valve A
- Shift solenoid valve B
- Each clutch
- Hydraulic control circuit
Diagnostic Trouble Code (DTC) Confirmation Procedure
CAUTION:
- Always drive vehicle at a safe speed.
- Be careful not to rev engine into the red zone on the tachometer.
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.
TESTING CONDITION:
Always drive vehicle on a level road to improve the accuracy of 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 - 1.5V
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 1ST GR FNCTN P0731 of DTC WORK SUPPORT mode for A/T with CONSULT-II and touch START.
4. Accelerate vehicle to 20 to 25 km/h (12 to 16 MPH) under the following condition and release the accelerator pedal completely.
THROTTLE POSI: Less than 1.0/8 (at all times during step 4)
Selector lever: D position (O/D ON)
- Check that GEAR shows 2 after releasing pedal.
5. Depress accelerator pedal to WOT (more than 7.0/8 of THROTTLE POSI) quickly from a speed of 20 to 25 km/h (12 to 16 MPH) until TESTING changes to STOP VEHICLE or COMPLETED. (It will take approximately 3 seconds.)
If the check result NG, appears on CONSULT-II screen, go to AT-511, Diagnostic Procedure.
If STOP VEHICLE appears on CONSULT-II screen, go to the following step.
Check that GEAR shows when depressing accelerator pedal to WOT.
If TESTING does not appear on CONSULT-II for a long time, select SELF-DIAG RESULTS for ENGINE. In case a 1st trip DTC other than P0731 is shown, refer to applicable TROUBLE DIAGNOSIS FOR DTC.
6. Stop vehicle.
7. Follow the instruction displayed. (Check for normal shifting referring to the table.)
8. 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-1ST
AT-1STSIG-01:
AT-1STSIG-01
TCM TERMINALS AND REFERENCE VALUE MEASURED BETWEEN EACH TERMINAL AND 25 OR 48 (TCM GROUND)
Diagnostic Procedure
1. CHECK VALVE RESISTANCE
1. Remove control valve assembly.
- Shift solenoid valve A
- Shift solenoid valve B
2. Check resistance between terminal cord assembly F30 terminals 1 and 9 and ground.
OK or NG
OK >> GO TO 2.
NG >> Repair or replace damaged parts.
2. CHECK VALVE OPERATION
1. Remove control valve assembly.
- Shift solenoid valve A
- Shift solenoid valve B
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 3.
NG >> Repair or replace shift solenoid valve assembly.
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 assembly.
4. CHECK DTC
Perform AT-508, Diagnostic Trouble Code (DTC) Confirmation Procedure.
OK or NG
OK >> INSPECTION END
NG >> Check transaxle internal components (clutch, brake, etc.).