Heavy Duty Transmission Troubleshooting Guide
OEM TROUBLESHOOTING GUIDE FOR ALLISON WT TROUBLE CODES

A. DISPLAYING OIL LEVEL INFORMATION

If the transmission you are troubleshooting has an oil level sensor, oil level information can be displayed on the shift selector. If the transmission does not have an oil level sensor, go to Section B.

Use the following procedure to display oil level sensor information:

1. Enter the oil level display mode:

  • Using a push-button shift selector, simultaneously press the � (up) and � (down) arrow buttons.
  • Using a lever shift selector, press the DISPLAY MODE button.

a. A two minute countdown begins after the following conditions are met:

  • Engine is at idle.
  • Sump oil is at operating temperature.
  • Transmission output shaft is stopped.
  • Transmission is in neutral.
  • Oil level sensor is functioning properly.
    -------------------------------------------------------------------------------- NOTE: Failure to meet any of the above conditions stops the two minute countdown. The shift selector displays one of the following codes to show the reason for the countdown interruption. Once all conditions have been met, the countdown resumes where it stopped.
CODE MEANING OF CODE
OL, --,50 Engine rpm too low
OL,--,59 Engine rpm too high
OL,--,65 Neutral not selected
OL,--,70 Sump oil temperature too low
OL,--,79 Sump oil temperature too high
OL,--,89 Output shaft rotation
OL,--,95 Oil level sensor failure

NOTE: The shift selector display can only display two characters at a time. One character is displayed under the MONITOR label and one under the SELECT label.

b. The display flashes and an 8, 7,.....1 count occurs during the two minute countdown. Oil level information displays after the countdown.

2. After two minutes the shift selector displays the oil level data as in the following examples:

CODE MEANING OF CODE
OL,OK,OK Oil lever correct
OL,LO,01 Oil level one quart low -- or as many quarts as needed
OL,HI,01 Oil level one quart high -- or as many quarts as overfilled

3. Exit the oil level display mode:
Using a push-button shift selector, press any range selection button.
Using a lever shift selector, press the DISPLAY MODE button twice.

B. CLEARING DIAGNOSTIC CODES

The DO NOT SHIFT light may remain illuminated due to false diagnostic codes generated during vehicle assembly. All false diagnostic codes must be cleared.

Use the following procedure to clear all diagnostic codes:

1. Enter the diagnostic mode:

  • Using a push-button shift selector (with oil level sensor), simultaneously press the �(up) and � (down) arrow buttons twice.
  • Using a push-button shift selector (without oil level sensor), simultaneously press the � (up) and � (down) arrow buttons once.
  • Using a lever shift selector (with oil level sensor), press the DISPLAY MODE button twice. Do not move the shift lever.
  • Using a lever shift selector (without oil level sensor), press the DISPLAY MODE button once. Do not move the shift lever.

2. Clear codes by holding the MODE button down -- approximately 10 seconds -- until the shift selector tone sounds twice.

3. Restart and drive the vehicle. If the DO NOT SHIFT light illuminates again, display the diagnostic codes as explained in Section C and record them for troubleshooting.

C. DISPLAYING DIAGNOSTIC CODES

1. Enter the diagnostic mode (refer to Section B, Step 1).

NOTE: If the DO NOT SHIFT light is illuminated, do not move the lever of a lever shift selector. If the lever is moved a continuous tone sounds until the lever is moved back to the position it was in when the DO NOT SHIFT light came on.

2. The code in the first of five code positions displays on the shift selector. The code display changes every two seconds, displaying the code list position, main code, and sub code. The display cycle repeats after the sub code is displayed. A sample code display using main code 25 and sub code 11 follows:

SELECT MONITOR

a. Code list position -- d1 d 1
b. Main code -- 25 2 5
c. Sub code -- 11 1 1

3. To view the next code, momentarily press the MODE button. Repeat to view each of the remaining codes.

4. To start over at the first code position, momentarily press the MODE button after the fifth code position is displayed.

5. To exit the diagnostic mode, do one of the following:

Do nothing; wait until the calibrated time has passed and the system automatically returns to normal operation.

  • Using a push-button shift selector, simultaneously press the � (up) and� (down) arrow buttons.
  • Using a push-button shift selector, press D (Drive), N (Neutral), or R (Reverse).
  • Using a lever shift selector, press the DISPLAY MODE button.
  • Using a lever shift selector, move the shift lever to any position other than the one it was in when the diagnostic display mode was activated.

NOTE: When a range is selected, that range will be commanded if not inhibited. If the selected range is inhibited the ECU illuminates the DO NOT SHIFT light and continues to command the current range. The lever shift selector tone sounds continuously until the lever is moved back to its original position.

NOTE: WT wiring harnesses must be procured from Allison Transmission. All of the above procedures (Sections A through C) apply to Allison harnesses only.

 

 

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