AutoShift®/UltraShift Gen3
TRTS0930 EN-US
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July 2024 - A

Front Box Control Test

Overview

This symptom-driven test is performed if a dash is displayed on the gear display, and there are no active or Inactive codes.

Detection

Turn the key on and watch the Gear Display. If the Gear Display shows “-” constantly, the Transmission Electronic Control Unit (TECU) was not able to confirm front box control.Any time the service light is flashing, go to Diagnostics Procedure.

Fallback

This fault causes an in-place fallback while moving, and it causes a failure during system initialization. A dash will appear on the Gear Display.

Possible Causes

This symptom can be caused by any of the following:

  • Low power to gear select motor
  • Electric shifter
  • Gear Select Sensor
  • Yoke / clutch / main shaft
  • Shift Bar housing
  • Dragging clutch
  • Torque locked in gear

Component Identification

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Front Box Control Test

A
Purpose:Visually observe the gear display after power-up.

  1. Key on.

  2. Depress clutch pedal (if equipped) half way to the floor.

  3. Place Shift Device in neutral.

  4. Observe Gear Display.

B
Purpose:Visually observe the gear display when placing the transmission into Drive.

  1. Key on.

  2. Place Shift Device in neutral.

  3. Depress clutch pedal (if equipped) half way to the floor. If it is a two pedal design apply the service brake.

  4. Select Drive

  5. Observe Gear Display.

    _Graphics/LineArt/trts0930s3p23b.png
C
Purpose:Measure battery voltage. Visually inspect the batteries, inline fuse and power and ground supplies at the batteries.

  1. Key off.

  2. Inspect starter/battery and in-line fuse holder connections for integrity.

  3. Measure voltage across batteries.

  • If voltage is 11 to 13 volts on a 12-volt system or 22 to 26 on a 24-volt system, proceed with battery load test. Repair or replace batteries as required and Go to Step D

  • If voltage is outside of range, repair or replace batteries and charging system as required. Repeat test.

D
Purpose:Verify proper ground path between the batteries and the transmission harness 4-way diagnostic connector.

  1. Locate diagnostic port on Transmission Harness.

  2. Key on.

  3. Measure voltage between Pin C and the battery negative post.

  • If voltage is 0.70 volts or less, Go to Step E

  • If voltage is outside of range, repair battery ground supply to TECU. Repeat test.

E
Purpose:Measure proper battery voltage at the transmission harness 4-way diagnostic connector.

  1. Locate diagnostic port on Transmission Harness.

  2. Key on.

  3. Measure voltage between Pin B and Pin C.

  • If voltage is within 0.6 volts of battery voltage, Go to Step F

  • If voltage is outside of range, repair battery power supply to TECU. Fuse may be blown. Repeat test.

F
Purpose:Measure proper ignition voltage at the transmission harness 4-way diagnostic connector.

  1. Key on.

  2. Measure voltage between Pin A and Pin C.

  • If voltage is within 0.6 volts of battery voltage, Go to Step G

  • If voltage is outside of range, repair Ignition power supply to TECU. Fuse may be blown. Repeat test.

G
Purpose:Remove Electric Shifter from the Shift Bar Housing and inspect the mechanical transmission.

  1. Key off.

  2. Remove Electric Shifter from Shift Bar housing.

  3. Inspect the Shift Bar housing:

    • Shift Blocks
    • Shift Rails
    • Inspect Electric Shifter for evidence of lube contamination.

    Note: See if the Shift Bar housing can engage two gears at the same time to verify interlock operation.

V
Purpose:Verify repair.

  1. Key off.

  2. Reconnect all connectors.

  3. Place Shift Control into neutral.

  4. Key on.

  • If Gear Display displays a solid N, test complete.

  • If Gear Display does not display a solid N, find error in testing, return to Go to Step A