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Thread: Duramax tranny shifting problem

  1. #11
    Daytona100
    Check the trans fuse for 12 volts when the fault occurs. Is the fault intermittant or constant? Does the dash cluster go inop at the same time? GM had a bad batch of ignition switches also pnp switches on the side of the trans. If you have access to a scanner check the indicated gear position compared to the actual gear position. Usually a electrical fault not something internal. Allison built the trans GM sublet the external electronics. Hencho en mexico. :idea: :idea:

  2. #12
    Sane Asylum
    Buy a Ford. :idea:
    Chevs don't come with a spare tranmission like the Fords..........You can actually repair them, they're not throwaways......

  3. #13
    Magic34
    Just give it more throttle

  4. #14
    Danhercules
    Maybe this will help some.
    2001 Chevrolet/Geo Chevy K Silverado - 4WD
    --------------------------------------------------------------------------------
    DTC P0722
    Circuit Description
    The speed sensors are variable reluctance devices that convert mechanical motion to an AC voltage. Each sensor consists of a wire coil wrapped around a pole piece that is adjacent to a permanent magnet. These elements are contained in a housing that is mounted adjacent to a rotating ferrous member. Two signal wires extend from one end of the housing and an exposed end of the pole piece is at the opposite end of the housing. The permanent magnet produces lines of flux around the pole piece. As a ferrous object, such as a gear tooth, approaches and passes through the gap at the end of the pole piece, an AC voltage pulse is induced in the wire coil. The transmission control module (TCM) calculates the frequency of these AC pulses and converts it to a speed value. The AC voltage generated varies from 150 millivolt at low speed to 15 volts at high speed. The signal wires from the sensor are formed as twisted pairs to cancel magnetically induced fields. The cable is also shielded to protect from voltage-related fields. Using two-wire differential inputs at the TCM eliminates noise from other sources.
    DTC P0722 is a type A DTC.
    Conditions for Running the DTC
    • DTC P0716, P0717, P0721, P0731, P0732, P0733, P0734, P0735, and P0736 are not active.
    • The components are powered and ignition voltage is greater than 9.0 volts and less than 18 volts.
    • Engine speed is greater than 200 RPM and less than 7,500 RPM for 5 seconds.
    • Turbine speed is greater than 1,050 RPM.
    • The shift selector indicates a valid range selection.
    Conditions for Setting the DTC
    DTC P0722 sets when the TCM detects one of the following conditions:
    • An unrealistically large change in output speed
    • An unrealistically low output speed
    Action Taken When the DTC Sets
    • The TCM illuminates the malfunction indicator lamp (MIL).
    • When failure occurs in a forward range and shifting is complete, the transmission remains in the current range. When failure occurs while in a forward range and the shift is in process, the transmission returns to the previous range, except in post-shift state, where the transmission will continue to the commanded range. When failure occurs in other conditions, the transmission shifts to 1st, 3rd or 5th. While diagnostic response is active, if the shift selector is moved to NEUTRAL or REVERSE or any other forward range, then the transmission will lock in NEUTRAL.
    • DTC P0722 will be stored in TCM history.
    • The TCM freezes shift adapts (DNA).
    • The TCM inhibits torque converter clutch (TCC) engagement.
    Conditions for Clearing the DTC
    A scan tool can clear the code from TCM history. The TCM automatically clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without failure.
    Diagnostic Aids
    • Inspect the wiring for poor electrical connections at the TCM. Inspect for the following conditions:
    - A bent terminal
    - A backed-out terminal
    - A damaged terminal
    - Poor terminal tension
    - A chafed wire
    - A broken wire inside the insulation
    • When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
    • You may have to drive the vehicle in order to experience a condition.
    • If the condition is intermittent, connect the scan tool and select the speed sensor indicated by the code. If the signal is erratic, investigate and eliminate the following:
    - Intermittent wiring connection
    - Excessive vibration, such as driveline or engine torsionals
    - Irregular sensor gap, such as a loose sensor, a loose tone wheel or a damaged tone wheel
    - Inspect that the speed sensor wiring consists of twisted pairs at the rate of 12-16 twists per 300 mm (12 in). These twists must extend the entire length of the wiring harness to within at least 50 mm (2 in) of the speed sensor connector.
    Test Description
    The numbers below refer to the step numbers on the diagnostic table.
    This step tests ignition voltage.
    This step tests the wiring at the TCM.
    This step tests for proper resistance at the output speed sensor resistance.
    Step
    Action
    Value
    Yes
    No
    Schematic Reference: Automatic Transmission Controls Schematics
    1
    Did you perform the Diagnostic System Check - Automatic Transmission?
    --
    Go to Step 2
    Go to Diagnostic System Check - Automatic Transmission
    2
    Install the scan tool.
    Turn ON the ignition, with the engine OFF.
    Important: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data.
    Record the DTC Freeze Frame and Failure Records.
    Clear the DTC.
    Using the scan tool, observe ignition voltage.
    Is voltage within the specified range?
    9-18 V
    Go to Step 3
    Go to DTC P0562 for low voltage or DTC P0563 for high voltage
    3
    Turn the ignition OFF.
    Disconnect the C2 connector (RED) from the TCM.
    Install the J 39700 breakout box and the J 43799 breakout box adapter at C2 connector.
    Using a DMM, measure the resistance between connector C2 terminals 15 and 16.
    Is the speed sensor resistance within the specified values?
    2WD: 2,600-3,160 ohms
    4WD: 1,420-2,140 ohms
    Go to Diagnostic Aids
    Go to Step 4
    4
    Disconnect the wiring harness from the output speed sensor.
    Using a DMM, measure the resistance between the speed sensor terminals.
    Is the speed sensor resistance within the specified values?
    2WD: 2,600-3,160 ohms
    4WD: 1,420-2,140 ohms
    Go to Step 5
    Go to Step 6
    5
    Repair the engine wiring harness. Refer to Wiring Repairs in Wiring Systems.
    Did you complete the repair?
    --
    Go to Step 7
    --
    6
    Important: Do not rotate the speed sensor in the retaining bracket. Orientation is fixed, and if changed, may cause improper operation.
    Replace the output speed sensor. Refer to Speed Sensor Replacement .
    Did you complete the replacement?
    --
    Go to Step 7
    --
    7
    Perform the following procedure in order to verify the repair:
    Clear the DTC.
    Using the scan tool, monitor the output speed sensor operation.
    Select Specific DTC.
    Enter DTC P0722.
    Has the test run and passed?
    System OK
    Go to Step 1
    --------------------------------------------------------------------------------
    Looks like we got a Diesel tweeker on here!!! Am I right Clyde? LOL :hammerhea

  5. #15
    ECeptor
    It's fixed. Turned out to be a bad wire to a wheel speed sensor that wasn't fully broken so it was transmitting a bad/intermittent signal.

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