P0729

A760F AUTOMATIC TRANSMISSION / TRANSAXLE: AUTOMATIC TRANSMISSION SYSTEM: P0729: Gear 6 Incorrect Ratio
P0729 - Gear 6 Incorrect Ratio

DESCRIPTION

The ECM uses signals from output speed sensor SP2 and input speed sensor NT to detect the actual gear position (1st, 2nd, 3rd, 4th, 5th or 6th gear). Then the ECM compares the actual gear with the shift schedule in the ECM memory to detect mechanical problems of the shift solenoid valves, valve body and automatic transmission (clutch, brake, gear, etc.).





HINT
- Gear positions in the event of a solenoid valve mechanical problem:






- Gear position during fail-safe operation:
- If any malfunction is detected, the ECM enters fail-safe mode and performs gear shifts as shown in the table below.






MONITOR DESCRIPTION

The ECM commands gear shifts by turning the shift solenoid valves ON/OFF and switching oil pressure to the valves in the valve body.

This DTC indicates that the sequence valve is locked with the spring stretched and that shifting to 6th gear is impossible.

MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS

All





HINT
*: Following conditions are met





Condition (A)





Condition (B)





TYPICAL MALFUNCTION THRESHOLDS

Both of the following conditions are met: Condition (A) and (B)

Condition (A)





Condition (B)





INSPECTION PROCEDURE

NOTICE:
Perform the universal trip to clear permanent DTCs DTC Check / Clear.

PROCEDURE

1. CHECK DTC OUTPUT (IN ADDITION TO DTC P0729)

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

(e) Read the DTCs using the Techstream.

Result





HINT
If any other codes besides P0729 are output, perform troubleshooting for those DTCs first.

B -- GO TO DTC CHART Automatic Transmission System - A760F
A -- Continue to next step.

2. PERFORM ACTIVE TEST USING TECHSTREAM (RUNNING TEST)

CAUTION:
This test should always be performed with at least 2 people.

NOTICE:
- Perform the test while the ATF temperature is between 50 and 80°C (122 and 176°F).
- Perform the test with the A/C turned off.
HINT
Using the Techstream to perform Active Tests allows relays, VSVs, actuators and other items to be operated without removing any parts. This non-intrusive functional inspection can be very useful because intermittent operation may be discovered before parts or wiring is disturbed. Performing Active Tests early in troubleshooting is one way to save diagnostic time. Data List information can be displayed while performing Active Tests.

(a) Warm up the engine.

(b) Turn the engine switch off.

(c) Connect the Techstream to the DLC3.

(d) Turn the engine switch on (IG).

(e) Turn the Techstream on.

(f) Enter the following menus: Powertrain / Engine and ECT / Active Test.

(g) According to the display on the Techstream, perform the Active Test.

HINT
While driving, the shift position can be forcibly changed with the Techstream.

Engine and ECT





HINT
- This test can be conducted when the vehicle speed is 50 km/h (30 mph) or less.
- The 4th to 5th and 5th to 6th up-shifts must be performed with the accelerator pedal released.
- The 6th to 5th and 5th to 4th down-shifts must be performed with the accelerator pedal released.
- Do not operate the accelerator pedal for at least 2 seconds after shifting and do not shift successively.
- The shift position commanded by the ECM is shown in the Data List display on the Techstream.
- Gear positions in the event of a solenoid valve mechanical problem:






OK:

Gear position changes in accordance with the tester command.

NG -- REPAIR OR REPLACE TRANSMISSION VALVE BODY ASSEMBLY
OK -- Continue to next step.

3. PERFORM ACTIVE TEST USING TECHSTREAM (SHIFT SOLENOID VALVE SLT)

NOTICE:
- Perform the test while the ATF temperature is between 50 and 80°C (122 and 176°F).
- Be careful to prevent the hose of SST from interfering with the exhaust pipe.
- Perform the test with the A/C off.
HINT
Using the Techstream to perform Active Tests allows relays, VSVs, actuators and other items to be operated without removing any parts. This non-intrusive functional inspection can be very useful because intermittent operation may be discovered before parts or wiring is disturbed. Performing Active Tests early in troubleshooting is one way to save diagnostic time. Data List information can be displayed while performing Active Tests.

(a) Remove the test plug from the transmission case and connect SST.





SST : 09992-00095

09992-00231

09992-00271

(b) Connect the Techstream to the DLC3.

(c) Start the engine and warm it up.

(d) Measure the line pressure with SST.

(e) Turn the Techstream on.

(f) Enter the following menus: Powertrain / Engine and ECT / Active Test.

(g) According to the display on the Techstream, perform the Active Test.

(h) Measure the line pressure.

Engine and ECT





HINT
*: Activate the Solenoid (SLT) in the Active Test is performed to check the line pressure changes by connecting SST to the automatic transmission, which is used in the Hydraulic Test Hydraulic Test as well. Note that the pressure values in the Active Test and Hydraulic Test are different.

OK:

The line pressure changes as specified when performing the Active Test.

NG -- REPLACE SHIFT SOLENOID VALVE SLT
OK -- Continue to next step.

4. CLEAR DTC AND PERFORM RUNNING TEST

(a) Clear the DTC DTC Check / Clear.

(b) Check for the DTC again after conducting the Monitor Drive Pattern Monitors, Trips, Drive Cycles and Readiness Codes.

OK:

No DTC code output.

NG -- REPAIR OR REPLACE AUTOMATIC TRANSMISSION ASSEMBLY Removal

OK -- END