VERACRUZ(EN) >2009 > G 3.8 DOHC > Automatic Transaxle System > Automatic Transaxle System > Troubleshooting>P0729 Gear 6 Incorrect Ratio  
General Description
The value of the input shaft speed should be equal to the value of the output shaft speed, when multiplied by the 6th gear ratio, while the transaxle is engaged in the 6th gear. For example, if the output speed is 1,000 rpm and the 6th gear ratio is 0.686, then the input speed is 686 rpm.
DTC Description
This code is set if the value of input shaft speed is not equal to the value of the output shaft, when multiplied by the 6th gear ratio, while the transaxle is engaged in 6th gear. This malfunction is mainly caused by mechanical troubles such as control valve sticking or solenoid valve malfunctioning rather than an electrical issue.
DTC Detecting Condition
Item
Detecting Condition
Possible cause
DTC Strategy
6th gear incorrect ratio
C2 clutch
B1 brake
Valve-body(C2, B1 pressure system)
TCU
Line pressure solenoid valve(SLT)
Shift control solenoid valve(SLC1, SLC2)
Enable Conditions
ATF temp. > 20°C
Output speed > 500rpm
TCU communication = normal
TPS >10%
Shift lever switch = "D" range
Shift gear = 6th gear
Threshold value
ㅣInput speed/6th gear ratio - output speed ㅣ≥200rpm
Diagnostic Time
More than 12 times × more than1sec
Fail Safe
Self learning control is inhibited
Locked in 3rd gear
Adaptive control is inhibited

Monitor Scantool Data
※ It is difficult to "STALL TEST" in 6th gear, so that Go to "Signal circuit inspection" procedure
Signal Circuit Inspection
1.
Connect Scantool.
2.
Engine "ON".
3.
Monitor the "INPUT & OUTPUT SPEED SENSOR" parameter on the scantool.
4.
Accelerate the Engine speed until about 2000 rpm in the 6th gear.

Specification : INPUT SPEED - (OUTPUT SPEED × GEAR RATIO) ≤ 200 RPM

5.
Does "INPUT & OUTPUT SPEED SENSOR" follow the reference data?

▶ Go to "Component Inspection" procedure.

▶ Check for electrical noise of circuit in INPUT & OUTPUT SPEED SENSOR or Replace INPUT & OUTPUT SPEED SENSOR. Repair as necessary and Go to "Verification of Vehicle Repair" procedure.

Component Inspection

1.
Connect Oil pressure gauge to "C2" port.
2.
Engine "ON".
3.
Drive a car with gear position "6".
4.
Compare it with reference data as below.

Specification : refer to Standard Oil Pressure Table as below

Standard Perssure
Shift Lever Position
Engine Status
Element
Specification (Kg/cm²)
"D" RANGE
IDLE
C1 CLUTCH
3.8 ~ 4.4
"R" RANGE
IDLE
C3 CLUTCH
5.9 ~ 7.1

5.
Is oil pressure value within specifications?

▶ Repair AUTO TRANSAXLE(Clutch or Brake) as necessary and Go to "Verification of Vehicle Repair" procedure.

▶ Replace AUTO TRANSAXLE (BODY CONTROL VALVE faulty) as necessary and Go to "Verification of Vehicle Repair" procedure.

NOTE)
When replacing the TCU, must perform the N position learning and the Initial learning. (refer to Troubleshooting's 'How to perform N position learning' and 'How to perform initial learning')
Verification of Vehicle Repair
After a repair, it is essential to verify that the fault has been corrected.
1.
Connect scan tool and select "Diagnostic Trouble Codes(DTCs)" mode
2.
Using a scantool, Clear DTC.
3.
Operate the vehicle within DTC Enable conditions in General information.
4.
Are you DTCs present?

▶ Go to the applicable troubleshooting procedure.

▶ System performing to specification at this time.