GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2009 🢒 Sierra Denali 🢒 Transmission 🢒 Automatic Transmission - Allison 🢒 DTC P0729 or P0731-P0736

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 Descriptors

DTC P0729: Incorrect 6th Gear Ratio

DTC P0731: Incorrect 1st Gear Ratio

DTC P0732: Incorrect 2nd Gear Ratio

DTC P0733: Incorrect 3rd Gear Ratio

DTC P0734: Incorrect 4th Gear Ratio

DTC P0735: Incorrect 5th Gear Ratio

DTC P0736: Incorrect Reverse Gear Ratio

Circuit/System Description

The vehicle speed sensor and automatic transmission turbine speed sensor contains a permanent magnet surrounded by a coil that gives off a continuous magnetic field. As the vehicle is driven, a speed sensor rotor located near the magnetic pickup of the speed sensor coil also rotates. This rotation produces a variable voltage signal that is proportional to the transmission turbine and output speed. The transmission control module (TCM) uses the signals to calculate the gear ratio. The TCM compares the computed ratio to the commanded gear ratio.

Conditions for Running the DTC
    • Output speed is greater than 200 RPM.
    • Ignition voltage is between 9-18 V.
    • Shift to range is completed.
    • DTCs P0716, P0717, P0721, P0722, P0877, and P0878 are not active.

Conditions for Setting the DTC

P0729

This DTC sets during steady state operation when the calculated sixth gear ratio differs from the known sixth gear ratio for more than 2 seconds.

P0731

This DTC sets during steady state operation when the calculated first gear ratio differs from the known first gear ratio for more than 2 seconds.

P0732

This DTC sets during steady state operation when the calculated second gear ratio differs from the known second gear ratio for more than 2 seconds.

P0733

This DTC sets during steady state operation when the calculated third gear ratio differs from the known third gear ratio for more than 2 seconds.

P0734

This DTC sets during steady state operation when the calculated fourth gear ratio differs from the known fourth gear ratio for more than 2 seconds.

P0735

This DTC sets during steady state operation when the calculated fifth gear ratio differs from the known fifth gear ratio for more than 2 seconds.

P0736

This DTC sets during steady state operation when the calculated reverse gear ratio differs from the known reverse gear ratio for more than 2 seconds.

Action Taken When the DTC Sets

P0729

    • The TCM requests the engine control module (ECM) to illuminate the malfunction indicator lamp (MIL).
    • The transmission will shift to fifth range.
    • While diagnostic response is active, if shift selector is moved to neutral, the transmission will shift to neutral. If the transmission is shifted to reverse (R), the transmission will shift to neutral. If the shift selector is moved to a forward range or reverse and transmission is compromised by overspeeding or direction change, transmission shifts to neutral.
    • DTC P0729 is stored in TCM history.
    • The TCM freezes shift adapts.
    • The TCM inhibits torque converter clutch (TCC) engagement.

P0731

    • The TCM requests the ECM to illuminate the MIL.
    • The transmission will shift to second range.
    • While diagnostic response is active, if shift selector is moved to neutral, the transmission will shift to neutral. If the transmission is shifted to reverse (R), the transmission will shift to neutral. If the shift selector is moved to a forward range or reverse and transmission is compromised by overspeeding or direction change, transmission shifts to neutral.
    • DTC P0731 is stored in TCM history.
    • The TCM freezes shift adapts.
    • The TCM inhibits TCC engagement.

P0732

    • The TCM requests the ECM to illuminate the MIL.
    • The transmission will shift to third range.
    • While diagnostic response is active, if shift selector is moved to neutral, the transmission will shift to neutral. If the transmission is shifted to reverse (R), the transmission will shift to reverse unless compromised by direction change, then transmission will shift to neutral. If the shift selector is moved to a forward range and transmission is compromised by overspeeding or direction change, transmission shifts to neutral.
    • DTC P0732 is stored in TCM history.
    • The TCM freezes shift adapts.
    • The TCM inhibits TCC engagement.

P0733

    • The TCM requests the ECM to illuminate the MIL.
    • The transmission will shift to fourth range.
    • While diagnostic response is active, if shift selector is moved to neutral, the transmission will shift to neutral. If the transmission is shifted to reverse (R), the transmission will shift to neutral. If the shift selector is moved to a forward range and transmission is compromised by overspeeding or direction change, transmission shifts to neutral.
    • DTC P0733 is stored in TCM history.
    • The TCM freezes shift adapts.
    • The TCM inhibits TCC engagement.

P0734

    • The TCM requests the ECM to illuminate the MIL.
    • The transmission will shift to fifth range.
    • While diagnostic response is active, if shift selector is moved to neutral, the transmission will shift to neutral. If the transmission is shifted to reverse (R), the transmission will shift to reverse unless compromised by direction change, then transmission will shift to neutral. If the shift selector is moved to a forward range and transmission is compromised by overspeeding or direction change, transmission shifts to neutral. If the transmission shifts to neutral due to overspeeding or direction change, the transmission will shift to first, third or fifth when the condition cleared.
    • DTC P0734 is stored in TCM history.
    • The TCM freezes shift adapts.
    • The TCM inhibits TCC engagement.

P0735

    • The TCM requests the ECM to illuminate the MIL.
    • The transmission will shift to fourth range.
    • While diagnostic response is active, if shift selector is moved to neutral, the transmission will shift to neutral. If the transmission is shifted to reverse (R), the transmission will shift neutral. If the shift selector is returned to forward and transmission is compromised by overspeeding or direction change, transmission shifts to neutral.
    • DTC P0735 is stored in TCM history.
    • The TCM freezes shift adapts.
    • The TCM inhibits TCC engagement.

P0736

    • The TCM requests the ECM to illuminate the MIL.
    • The transmission will shift to neutral.
    • DTC P0736 is stored in TCM history.

Conditions for Clearing the DTC

DTC P0729, P0731, P0732, P0733, P0734, P0735, and P0736 are Type A DTCs.

Diagnostic Aids
    • You will have to drive the vehicle in order to experience a condition.
    • Incorrect ratio DTCs may indicate a component condition with piston seals, clutch plates, or solenoids.
    • Incorrect ratio DTCs may be caused by a faulty speed sensor signal.

Reference Information

Schematic Reference

Automatic Transmission Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

    •  Transmission General Description
    •  Transmission Component and System Description
    •  Electronic Component Description

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification
  1. Inspect the transmission fluid level. Refer to Transmission Fluid Check.
  2. Perform a road test. Refer to Road Test.
  3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed on the Freeze Frame/Failure Records data.

Circuit/System Testing

    Note: You must perform the Circuit/System Verification first.

  1. Perform a line pressure test. Refer to Line Pressure Check.
    2. ⇒If line pressure is low in all ranges, refer to Low Main Line Pressure in All Ranges.
    ⇒ If line pressure is low in a specific range or ranges, refer to Low Main Line Pressure in Specific Ranges, Normal Pressure in Other Ranges.

    Warning: Chock the wheels to prevent the vehicle from moving. Failure to chock the wheels can cause personal injury when the electrical system is repaired.

  2. Perform the clutch test. Refer to Clutch Test.
    3. ⇒If not the specified value, refer to Excessive Slippage and Clutch Chatter.
  3. If the above test is normal, refer to Functional Test.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Speed Sensor Replacement, 2WD
    •  Vehicle Speed Sensor Replacement, 4WD
    •  Control Valve Solenoid Replacement for PCS1 or PCS2 replacement.
    •  Control Valve Body Cleaning and Inspection

Repair Verification

If another DTC is present, refer to Diagnostic Trouble Code (DTC) List - Vehicle and perform the appropriate diagnostic procedure.