Toyota Tundra Service Manual: Gear 6 Incorrect Ratio (P0729)

DESCRIPTION

The ECM uses signals from the 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.).

DTC Code

DTC Detection Condition

Trouble Area

P0729

  • 6th gear shift malfunction:
  • The ECM determines there is a malfunction when both of the following conditions are met (2-trip detection logic):

(a) When the ECM directs the transmission to switch to 5th gear, the actual gear is shifted to 5th.

(b) When the ECM directs the transmission to switch to 6th gear, the actual gear is shifted to 4th.

  • Valve body is blocked or stuck (sequence valve)
  • Shift solenoid valve SLT remains open or closed
  • Automatic transmission (clutch, brake, gear, etc.)

HINT:

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

    ECM gear shift command

    1st

    2nd

    3rd

    4th

    5th

    6th

    Actual gear position under malfunction

    1st

    2nd

    3rd

    4th

    5th

    4th

  • Gear position during fail-safe operation:

    If any malfunction is detected, the ECM changes into the fail-safe mode to shift into the gear positions as shown in the table below.

    Gear position under normal conditions

    1st

    2nd

    3rd

    4th

    5th

    6th

    Actual gear position under fail-safe mode

    1st

    2nd

    3rd

    3rd

    3rd

    3rd

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 in the direction the spring stretches and that shifting to 6th gear is impossible.

MONITOR STRATEGY

Related DTCs

P0729: Gear 6 incorrect ratio (Sequence valve) / Functional check

Required sensors/Components

Sequence valve

Frequency of operation

Continuous

Duration

0.4 seconds

MIL operation

2 driving cycles

Sequence of operation

None

TYPICAL ENABLING CONDITIONS

All

The monitor will run whenever the following DTCs are not present

P0717 (Turbine speed sensor circuit)

P0722 (Output speed sensor circuit)

P0710, P0712, P0713, P2740, P2742, P2743 (ATF temperature sensor circuit)

P0973, P0974 (Shift solenoid valve S1 circuit)

P0976, P0977 (Shift solenoid valve S2 circuit)

P0979, P0980 (Shift solenoid valve S3 circuit)

P0982, P0983 (Shift solenoid valve S4 circuit)

P0985, P0986 (Shift solenoid valve SR circuit)

P0748 (Shift solenoid valve SL1 circuit)

P0778 (Shift solenoid valve SL2 circuit)

P0115, P0116, P0117, P0118, P011B (ECT (Engine coolant temperature) sensor circuit)

P0327, P0328, P032C, P032D (KCS sensor circuit)

ETCS (Electric Throttle Control System)

Not system down

Transmission position

"D"

Duration time from shifting "N" to "D"

4 seconds or more

ECT

40°C (104°F) or higher

Spark advance from max. retard timing by KCS control

0° crankshaft angle or more

Engine

Starting

Calculated load value

7.75% or more (A/C off)

7.75% or more (A/C on)

Input speed/output speed (NT/NO)

NT: Input (Turbine) speed

NO: Internal counter shaft speed

3.30 to 7.50

or

1.91 to 2.35

or

1.28 to 1.53

or

0.93 to 1.07

or

0.65 to 0.79

or

0.51 to 0.65

Condition (A)

ECM selected gear

5th

Vehicle speed

2 km/h (1.2 mph) or more

Throttle valve opening angle

5% or more at 2000 rpm

(Conditions vary with engine speed)

Condition (B)

ECM selected gear

6th

Vehicle speed

2 km/h (1.2 mph) or more

Throttle valve opening angle

5% or more at 2000 rpm

(Conditions vary with engine speed)

TYPICAL MALFUNCTION THRESHOLDS

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

Condition (A)

Turbine speed / Output speed (NT / NO)

0.65 or more, and 0.79 or less

(This means actual gear is 5th)

Condition (B)

Turbine speed / Output speed (NT / NO)

0.93 or more, and 1.07 or less

(This means actual gear is 4th)

CAUTION / NOTICE / HINT

NOTICE:

Perform the universal trip to clear permanent DTCs (See page ).

PROCEDURE

1.

CHECK DTC OUTPUT (IN ADDITION TO DTC P0729)

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

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

(e) Read the DTCs using the Techstream.

Result

Result

Proceed to

Only P0729 is output

A

P0729 and other DTCs are output

B

HINT:

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

B

GO TO DTC CHART

A

2.

PERFORM ACTIVE TEST USING TECHSTREAM (RUNNING TEST)

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 ignition switch off.

(c) Connect the Techstream to the DLC3.

(d) Turn the ignition switch to ON.

(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

Tester Display

Test Part

Control Range

Diagnostic Note

Control the Shift Position

Operate shift solenoid valves and set each shift position

  • Press "→" button: Shift up
  • Press "←" button: Shift down

Possible to check operation of the shift solenoid valves.

[Vehicle Condition]

50 km/h (30 mph) or less

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:

    Tester gear shift command

    1st

    2nd

    3rd

    4th

    5th

    6th

    Actual gear position under malfunction

    1st

    2nd

    3rd

    4th

    5th

    4th

OK:

Gear position changes in accordance with the tester command.

NG

REPAIR OR REPLACE TRANSMISSION VALVE BODY ASSEMBLY

OK

3.

PERFORM ACTIVE TEST USING TECHSTREAM (SHIFT SOLENOID VALVE SLT)

NOTICE:

  • Perform the test while the ATF temperature is 50 to 80°C (122 to 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 center of the right side of the transmission case and connect SST.

SST: 09993-19015

09993-00010

09993-00040

(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

Tester Display

Test Part

Control Range

Diagnostic Note

Activate the Solenoid (SLT)*

Operate the shift solenoid SLT and raise line pressure

ON or OFF

HINT:

  • OFF: Line pressure up (when Active Test "Activate the Solenoid (SLT)" is performed, ECM commands SLT solenoid to turn off)
  • ON: No action (normal operation)

[Vehicle Condition]

  • Vehicle stopped
  • Engine idling

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 (See page ) as well. Please 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.

Text in Illustration

*1

Test Plug

NG

REPLACE SHIFT SOLENOID VALVE SLT

OK

4.

CLEAR DTC AND PERFORM RUNNING TEST

(a) Clear the DTC (See page ).

(b) Check for the DTC again after conducting the Monitor Drive Pattern (See page ).

OK:

No DTC code output.

OK

END

NG

REPAIR OR REPLACE AUTOMATIC TRANSMISSION ASSEMBLY

    Output Speed Sensor Circuit No Signal (P0722)

    Pressure Control Solenoid "A" Electrical (Shift Solenoid Valve SL1) (P0748)

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