Diagnostic Instructions

•	Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

•	Review Strategy Based Diagnosis for an overview of the diagnostic approach.

•	Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0729

6th Gear Ratio Incorrect

Diagnostic Fault Information

Component	Condition	DTCs
Valve Body Assembly	• Incorrect transmission fluid level • Clogged hydraulic system • Plugged or restricted passages • Gasket leaking	P0729, P0731, P0732, P0733, P0734, P0735, P0736, P0780, P1731
Line Pressure Control Solenoid Valve	• Incorrect transmission fluid level • Clogged hydraulic system • Mechanically stuck in the applied position • Gasket leaking	P0729, P0731, P0732, P0733, P0734, P0735, P0736, P0780, P1731
Shift Solenoid Valve	• Incorrect transmission fluid level • Clogged hydraulic system • Mechanically stuck in the applied position • Gasket leaking	P0729, P0731, P0732, P0733, P0734, P0735, P0736, P0780, P1731
Pressure Control Solenoid Valve	• Incorrect transmission fluid level • Clogged hydraulic system • Mechanically stuck in the applied position • Gasket leaking	P0729, P0731, P0732, P0733, P0734, P0735, P0736, P0780, P1731
Fluid Pump Cover Assembly	Fluid pump cover vanes and fluid pump rotor broken	P0729, P0731, P0732, P0733, P0734, P0735, P0736, P0780, P1731

Circuit/System Description

The shift control solenoid assembly (SLC1, SLC2, SLC3, SLB1) and the line pressure control solenoid (SLT) are installed on the front valve body. The solenoids linearly control hydraulic pressure in response to signals output from the transmission control module (TCM). SLC1, SLC2, SLC3, SLB1 controls hydraulic pressure to the clutches (C1, C2, C3) and brake (B1) for smooth shifting. According to each shift control solenoid assembly, the transmission shifts from 1st gear to 6th gear and vice versa. As a fail-safe function, if any shift control solenoid assembly abnormality occurs, the TCM will disable the current to the solenoids.

Conditions for Running the DTC

•	The ignition voltage is 10.2-15.5 V.

•	The engine speed is greater than 400 RPM for 2 s.

•	The transmission is not in emergency mode.

•	TCM communication is normal.

•	Transmission fluid temperature is higher than 20°C (68°F).

•	DTCs P0716. P0717, P0721 and P0722 are not set.

Conditions for Setting the DTC

•	Driving in D range, 6th gear.

•	Output speed more than 500 RPM.

•	Throttle position more than 10%.

•	Measured gear ratio deviates more than 20% from expected ratio.

•	Measured gear ratio deviates within 4% from 4th or 5th gear ratio.

•	Determined after 12 times lasting 1 s or more.

Action Taken When the DTC Sets

•	DTC P0729 is a Type C DTC.

•	Torque limitation in "D" range 150 Nm (110 lb ft), in "R" range 170 Nm (125 lb ft).

•	The TCM freezes transmission adaptive functions.

•	The TCM turns OFF all solenoids.

•	The TCM allows the vehicle after a stop to operate only in the second gear and “R” range.

Conditions for Clearing the DTC

•	DTC P0729 is a Type C DTC.

•	Measured gear ratio deviates less than 4% from expected ratio.

Diagnostic Aids

Ensure the transmission fluid level, color and odor is correct and there are no leaks. If there are any other transmission DTCs set, diagnose those first.

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

•	Circuit Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

Description and Operation

Transmission Component and System Description

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1.	Verify the transmission fluid level, color and odor is correct.

2.

Operate the vehicle to induce a shift from fifth to sixth gear while observing the following scan tool parameters. The scan tool parameters has to change the proper value referring to the current gear, compare the proper values with: transmission system description and operation. Refer to Transmission System Description and Operation (M36 and MXE). Perform this action 2 times.

•

Clutch Pressure Control Solenoid Valve 1 Current

•

Clutch Pressure Control Solenoid Valve 2 Current

•

Clutch Pressure Control Solenoid Valve 3 Current

•

Brake Band Pressure Control Solenoid Valve Current

•

Shift Solenoid Valve 1

•

Shift Solenoid Valve 2

3.	If the scan tool parameter does not change the proper value and no other DTCs than P0729, P0731, P0732, P0733, P0734, P0735, P0736, P0780, P1731 is set, go to Circuit/System Testing.

4.	If any other DTC is set, diagnose that DTC first.

Circuit/System Testing

Dynamic Test

1.	Perform the line pressure check. Refer to Line Pressure Check.

2.	Perform the transmission fluid check. Refer to Transmission Fluid Level and Condition Check.

3.	If all circuits test normal, replace the K71 Transmission Control Module. Verify the DTC does not reset.

4.	If the DTC resets replace the control valve body.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

•	Control valve body replacement-Refer to Control Valve Body Replacement for replacement, setup, and programming.

•	TCM-Refer to Control Module References for replacement, setup and programming.

•	Perform the Transmission Adaptive Functions.