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Allison-Transmission-Fault-Code-List-(How-To-Read-Codes)

Allison Transmission Fault Code List (How To Read Codes)

To make work easier auto component makers have relied on the fault code system. These fault codes are supposed to cu the guesswork out of doing car repairs. However, like Allison, many companies have their own fault code system and it doesn’t line up with the SPN FMI code system.

The Allison fault code system uses 3 letters to identify the source and location of the problem. Those letters are C, P, and U. However, be careful of the instructions as they may throw the letter D in there as well.

To learn these codes and how to read them, just continue to read our article. It has the information you want to know about so you can figure out your transmission issue faster than you could before the fault code system was implemented.

Allison Fault Code List
Allison Transmission Fault Code List
How To Read Allison Transmission Codes
How To Reset Allison Transmission Fault Codes
Clearing Allison Transmission Codes

Allison Transmission Fault Code List

1. Diagnostic Transmission Codes- (D)

Main code Sub code Description
13 12 ECU INPUT VOLTAGE LOW

 13 ECU INPUT VOLTAGE MEDIUM LOW

 23 ECU INPUT VOLTAGE HIGH
14 12 OIL LEvEL SENSOR, FAILED LOW

 23 OIL LEVEL SENSOR, FAILED HIGH
21 12 THROTTLE POSITION SENSOR, FAILED LOW

 23 THROTTLE POSITION SENSOR, FAILED HIGH
22 14 ENGINE SPEED SENSOR

 15 TURBINE SPEED SENSOR

 16 OUTPUT SPEED SENSOR
23 12 PRIMARY SHIFT SELECTOR FAULT

 13 PRIMARY SHIFT SELECTOR MODE FAULT

 14 SECONDARY SHIFT SELECTOR FAULT

 15 SECONDARY SHIFT SELECTOR MODE FAULT

 16 SHIFT SELECTOR DISPLAY LINE FAULT
24 12 SUMP FLUID TEMPERATURE, COLD

 23 SUMP FLUID TEMPERATURE, HOT
25 00 OUTPUT SPEED SENSOR @ 0 RPM, LOW

 11 OUTPUT SPEED SENSOR @ 0 RPM, 1ST

 22 OUTPUT SPEED SENSOR @ 0 RPM, 2ND

 33 OUTPUT SPEED SENSOR @ 0 RPM, 3RD

 44 OUTPUT SPEED SENSOR @ 0 RPM, 4TH

 55 OUTPUT SPEED SENSOR @ 0 RPM, 5TH

 66 OUTPUT SPEED SENSOR @ 0 RPM, 6TH

 77 OUTPUT SPEED SENSOR @ 0 RPM, REvERSE
26 00 THROTTLE SOURCE NOT DETECTED

 11 ENGINE COOLANT SOURCE NOT DETECTED
32 00 C3 PRESSURE SWITCH OPEN IN LOW

 33 C3 PRESSURE SWITCH OPEN IN 3RD

 55 C3 PRESSURE SWITCH OPEN IN 5TH

 77 C3 PRESSURE SWITCH OPEN IN REVERSE
33 12 SUMP OIL TEMPERATURE SENSOR, FAILED LOW

 23 SUMP OIL TEMPERATURE SENSOR, FAILED HIGH
34 12 CALIBRATION COMPATIBILITY WRONG

 13 CALIBRATION BLOCK CHECKSUM

 14 POWER OFF BLOCK CHECKSUM

 15 DIAGNOSE QUEUE BLOCK CHECKSUM

 16 REAL TIME BLOCK CHECKSUM

 17 CUSTOMER MODIFIABLE CONSTANTS CHECKSUM
35 00 POWER INTERRUPTION

 16 REAL TIME WRITE INTERRUPTION
36 00 HARDWARE/SOFTWARE NOT COMPATIBLE

 01 TID NOT COMPATIBLE W/HARDWARE/SOFTWARE

 02 TID DID NOT COMPLETE
42 12 A SOLENOID SHORTED TO BATTERY

 13 B SOLENOID SHORTED TO BATTERY

 14 C SOLENOID SHORTED TO BATTERY

 15 D SOLENOID SHORTED TO BATTERY

 16 E SOLENOID SHORTED TO BATTERY

 21 F SOLENOID SHORTED TO BATTERY

 22 G SOLENOID SHORTED TO BATTERY

 23 H SOLENOID SHORTED TO BATTERY

 24 J SOLENOID SHORTED TO BATTERY

 26 N SOLENOID SHORTED TO BATTERY
44 12 A SOLENOID SHORTED TO GROUND

 13 B SOLENOID SHORTED TO GROUND

 14 C SOLENOID SHORTED TO GROUND

 15 D SOLENOID SHORTED TO GROUND

 16 E SOLENOID SHORTED TO GROUND

 21 F SOLENOID SHORTED TO GROUND

 22 G SOLENOID SHORTED TO GROUND

 23 H SOLENOID SHORTED TO GROUND

 24 J SOLENOID SHORTED TO GROUND

 26 N SOLENOID SHORTED TO GROUND
45 12 A SOLENOID CIRCUIT OPEN

 13 B SOLENOID CIRCUIT OPEN

 14 C SOLENOID CIRCUIT OPEN

 15 D SOLENOID CIRCUIT OPEN

 16 E SOLENOID CIRCUIT OPEN

 21 F SOLENOID CIRCUIT OPEN

 22 G SOLENOID CIRCUIT OPEN

 23 H SOLENOID CIRCUIT OPEN

 24 J SOLENOID CIRCUIT OPEN

 26 N SOLENOID CIRCUIT OPEN


Main code Sub code Description
46 21 F SOLENOID CIRCUIT OvERCURRENT

 26 N & H SOLENOID CIRCUIT OvERCURRENT

 27 A-HI SOLENOID CIRCUIT OvERCURRENT
51 01 OFFgOINg RATIO TEST, LOW TO 1

 10 OFFGOING RATIO TEST, 1 TO LOW

 12 OFFGOING RATIO TEST, 1 TO 2

 21 OFFGOING RATIO TEST, 2 TO 1

 23 OFFGOING RATIO TEST, 2 TO 3

 24 OFFGOING RATIO TEST, 2 TO 4

 35 OFFGOING RATIO TEST, 3 TO 5

 42 OFFGOING RATIO TEST, 4 TO 2

 43 OFFGOING RATIO TEST, 4 TO 3

 45 OFFGOING RATIO TEST, 4 TO 5

 46 OFFGOING RATIO TEST, 4 TO 6

 53 OFFGOING RATIO TEST, 5 TO 3

 64 OFFGOING RATIO TEST, 6 TO 4

 65 OFFGOING RATIO TEST, 6 TO 5

 XY OFFGOING RATIO TEST, X TO Y
52 01 OFFGOING C3PS TEST, LOW TO 1

 08 OFFGOING C3PS TEST, LOW TO N1

 32 OFFGOING C3PS TEST, 3 TO 2

 34 OFFGOING C3PS TEST, 3 TO 4

 54 OFFGOING C3PS TEST, 5 TO 4

 56 OFFGOING C3PS TEST, 5 TO 6

 71 OFFGOING C3PS TEST, REVERSE TO 1

 72 OFFGOING C3PS TEST, REVERSE TO 2

 78 OFFGOING C3PS TEST, REVERSE TO N1

 99 OFFGOING C3PS TEST, N3 TO N2

 XY OFFGOING C3PS TEST, X TO Y
53 08 OFFGOING SPEED TEST, LOW TO N1

 09 OFFGOING SPEED TEST, L TO NNC

 18 OFFGOING SPEED TEST, 1 TO N1

 19 OFFGOING SPEED TEST, 1 TO RELS

 28 OFFGOING SPEED TEST, 2 TO N1

 29 OFFGOING SPEED TEST, 2 TO N2

 38 OFFGOING SPEED TEST, 3 TO N1

 39 OFFGOING SPEED TEST, 3 TO N3

 48 OFFGOING SPEED TEST, 4 TO N1

 49 OFFGOING SPEED TEST, 4 TO N3

 58 OFFGOING SPEED TEST, 5 TO N1

 59 OFFGOING SPEED TEST, 5 TO N3

 68 OFFGOING SPEED TEST, 6 TO N1

 69 OFFGOING SPEED TEST, 6 TO N4

 78 OFFGOING SPEED TEST, REVERSE TO N1

 99 OFFGOING SPEED TEST, N2 TO N3 OR N3 TO N2

 XY OFFGOING SPEED TEST, X TO Y
54 01 ONCOMING RATIO TEST, LOW TO 1

 07 ONCOMING RATIO TEST, LOW TO REVERSE

 10 ONCOMING RATIO TEST, 1 TO LOW

 12 ONCOMING RATIO TEST, 1 TO 2

 17 ONCOMING RATIO TEST, 1 TO REVERSE

 21 ONCOMING RATIO TEST, 2 TO 1

 23 ONCOMING RATIO TEST, 2 TO 3

 24 ONCOMING RATIO TEST, 2 TO 4

 27 ONCOMING RATIO TEST, 2 TO REVERSE

 32 ONCOMING RATIO TEST, 3 TO 2

 34 ONCOMING RATIO TEST, 3 TO 4

 35 ONCOMING RATIO TEST, 3 TO 5

 42 ONCOMING RATIO TEST, 4 TO 2

 43 ONCOMING RATIO TEST, 4 TO 3

 45 ONCOMING RATIO TEST, 4 TO 5

 46 ONCOMING RATIO TEST, 4 TO 6

 53 ONCOMING RATIO TEST, 5 TO 3

 54 ONCOMING RATIO TEST, 5 TO 4

 56 ONCOMING RATIO TEST, 5 TO 6

 64 ONCOMING RATIO TEST, 6 TO 4

 65 ONCOMING RATIO TEST, 6 TO 5

 70 ONCOMING RATIO TEST, REV. TO LOW

 71 ONCOMING RATIO TEST, REVERSE TO 1

 72 ONCOMING RATIO TEST, REVERSE TO 2

 80 ONCOMING RATIO TEST, N1 TO LOW

 81 ONCOMING RATIO TEST, N1 TO 1

 82 ONCOMING RATIO TEST, N1 TO 2

 83 ONCOMING RATIO TEST, N1 TO 3


Main code Sub code Description
54 85 ONCOMING RATIO TEST, N1 TO 5

 86 ONCOMING RATIO TEST, N1 TO 6

 87 ONCOMING RATIO TEST, N1 TO REVERSE

 92 ONCOMING RATIO TEST, N2 TO 2

 93 ONCOMING RATIO TEST, N3 TO 3

 95 ONCOMING RATIO TEST, N3 TO 5

 96 ONCOMING RATIO TEST, N4 TO 6

 XY ONCOMING RATIO TEST, X TO Y
55 07 ONCOMING C3PS TEST, LOW TO REVERSE

 17 ONCOMING C3PS TEST, 1 TO REVERSE

 27 ONCOMING C3PS TEST, 2 TO REVERSE

 87 ONCOMING C3PS TEST, N1 TO REVERSE

 97 ONCOMING C3PS TEST, NVL TO REVERSE

 XY ONCOMING C3PS TEST, X TO Y
56 00 LOW RANGE VERIFICATION TEST

 11 1ST RANGE VERIFICATION TEST

 22 2ND RANGE VERIFICATION TEST

 33 3RD RANGE VERIFICATION TEST

 44 4TH RANGE VERIFICATION TEST

 55 5TH RANGE VERIFICATION TEST

 66 6TH RANGE VERIFICATION TEST

 77 REVERSE RANGE VERIFICATION TEST
57 11 1ST RANGE VERIFICATION C3PS TEST

 22 2ND RANGE VERIFICATION C3PS TEST

 44 4TH RANGE VERIFICATION C3PS TEST

 66 6TH RANGE VERIFICATION C3PS TEST

 88 N1 RANGE VERIFICATION C3PS TEST

 99 N2 OR N4 RANGE VERIFICATION C3PS TEST
61 00 RETARDER OIL TEMPERATURE, HOT
62 12 RETARDER TEMP. SENSOR, FAILED LOW

 23 RETARDER TEMP. SENSOR, FAILED HIGH

 32 ENGINE COOLANT TEMP. SENSOR, FAILED LOW

 33 ENGINE COOLANT TEMP. SENSOR, FAILED HIGH
63 00 INPUT FUNCTION FAULT

 26 KICKDOWN INPUT, FAILED ON

 40 SERVICE BRAKE STATUS INPUT, FAILED ON

 41 PUMP/PACK AND NEUTRAL GENERALPURPOSE INPUT

 47 RELS INPUT, FAILED ON
64 12 RETARDER MODULATION SENSOR, FAILED LOW

 23 RETARDER MODULATION SENSOR, FAILED HIGH
65 00 ENGINE RATING TOO HIGH

 11 ENGINE NOT RESPONDING TO LRTPTORQUE REDUCTION

 12 ENGINE NOT RESPONDING TO DEFAULTTRANSMISSION TORQUE LIMIT
66 00 SERIAL COMMUNICATION INTERFACE FAULT

 11 S. C. I. ENGINE COOLANT SOURCE FAULT

 22 J1939 RETARDER REQUEST FAULT

 33 J1939 DRIVER DEMAND TORQUE FAULT

 34 ENGINE NOT RESPONDING TO J1939SEM CONTROL
69 27 A-HIGH SWITCH INOPERATIVE IN ECU

 28 F-HIGH SWITCH INOPERATIVE IN ECU

 29 N & H-HIGH SWITCH INOPERATIVE IN ECU

 33 COMPUTER OPERATING PROPERLY TIMEOUTIN ECU

 34 ECU WRITE TIMEOUT

 35 ECU CHECKSUM TEST

 36 RAM SELF TEST IN ECU

 39 COMMUNICATION CHIP ADDRESSING ERROR

 41 I/O ASIC ADDRESSING TEST IN ECU

 42 SPI OUTPUT FAILURE

 43 SPI INPUT FAILURE
70 12 MINOR LOOP OVERRUN IN SOFTWARE

 13 ILLEGAL WRITE TO ADDRESS $0000

 14 MAJOR LOOP OVERRUN IN SOFTWARE

2. Diagnostic transmission Codes- (C, P, & U)

Code Description
C1312 RETARDER REQUEST SENSOR, FAILED LOW
C1313 RETARDER REQUEST SENSOR, FAILED HIGH
P0122 PEDAL POSITION SENSOR, LOW VOLTAGE
P0123 PEDAL POSITION SENSOR, HIGH VOLTAGE
P0218 TRANSMISSION FLUID OVER TEMPERATURE
P0602 TCM NOT PROgRAMMED
P0610 TCM VEHICLE OPTIONS (TRANSID) ERROR
P0613 TCM PROCESSOR
P0614 TORQUE CONTROL DATA MISMATCH—ECM/TCM
P0634 TCM INTERNAL TEMPERATURE TOO HIGH
P063E AUTO CONFIGURATION THROTTLE INPUT NOT PRESENT
P063F AUTO CONFIGURATION ENGINE COOLANT TEMP INPUT NOT PRESENT
P0658 ACTUATOR SUPPLY VOLTAGE 1 (HSD1), LOW
P0659 ACTUATOR SUPPLY VOLTAGE 1 (HSD1), HIGH
P0701 TRANSMISSION CONTROL SYSTEM PERFORMANCE
P0702 TRANSMISSION CONTROL SYSTEM ELECTRICAL (TRANSID)
P0703 BRAKE SWITCH CIRCUIT MALFUNCTION
P0708 TRANSMISSION RANGE SENSOR, HIGH
P070C TRANSMISSION FLUID LEVEL SENSOR, LOW
P070D TRANSMISSION FLUID LEVEL SENSOR, HIGH
P0711 TRANSMISSION FLUID TEMPERATURE SENSOR PERFORMANCE
P0712 TRANSMISSION FLUID TEMPERATURE SENSOR, LOW
P0713 TRANSMISSION FLUID TEMPERATURE SENSOR, HIGH
P0716 TURBINE SPEED SENSOR PERFORMANCE
P0717 TURBINE SPEED SENSOR, NO SIGNAL
P0719 BRAKE SWITCH ABS, INPUT LOW
P071A RELS INPUT, FAILED ON
P071D GENERAL PURPOSE FAULT
P0721 OUTPUT SPEED SENSOR PERFORMANCE
P0722 OUTPUT SPEED SENSOR, NO SIGNAL
P0726 ENGINE SPEED SENSOR PERFORMANCE
P0727 ENGINE SPEED SENSOR, NO SIGNAL
P0729 INCORRECT 6TH GEAR RATIO
P0731 INCORRECT 1ST GEAR RATIO
P0732 INCORRECT 2ND GEAR RATIO
P0733 INCORRECT 3RD GEAR RATIO
P0734 INCORRECT 4TH GEAR RATIO
P0735 INCORRECT 5TH GEAR RATIO
P0736 INCORRECT REVERSE GEAR RATIO
P0741 TORQUE CONVERTER CLUTCH SYSTEM, STUCK OFF
P0776 PRESSURE CONTROL SOLENOID 2, STUCK OFF
P0777 PRESSURE CONTROL SOLENOID 2, STUCK ON
P0796 PRESSURE CONTROL SOLENOID 3, STUCK OFF
P0797 PRESSURE CONTROL SOLENOID 3, STUCK ON
P0842 TRANSMISSION PRESSURE SWITCH 1, LOW
P0843 TRANSMISSION PRESSURE SWITCH 1, HIGH
P0880 TCM POWER INPUT SIGNAL
P0881 TCM POWER INPUT SIGNAL PERFORMANCE
P0882 TCM POWER INPUT SIGNAL, LOW
P0883 TCM POWER INPUT SIGNAL, HIGH
P0894 TRANSMISSION COMPONENT SLIPPING
P0960 PRESSURE CONTROL SOLENOID MAIN MOD CONTROL, OPEN
P0962 PRESSURE CONTROL SOLENOID MAIN MOD CONTROL, LOW
P0963 PRESSURE CONTROL SOLENOID MAIN MOD CONTROL, HIGH
P0964 PRESSURE CONTROL SOLENOID 2 CONTROL, OPEN
P0966 PRESSURE CONTROL SOLENOID 2 CONTROL, LOW
P0967 PRESSURE CONTROL SOLENOID 2 CONTROL, HIGH
P0968 PRESSURE CONTROL SOLENOID 3 CONTROL, OPEN
P0970 PRESSURE CONTROL SOLENOID 3 CONTROL, LOW
P0971 PRESSURE CONTROL SOLENOID 3 CONTROL, HIGH
P0973 SHIFT SOLENOID 1 CONTROL, LOW
P0974 SHIFT SOLENOID 1 CONTROL, HIGH
P0975 SHIFT SOLENOID 2 CONTROL, OPEN
P0976 SHIFT SOLENOID 2 CONTROL, LOW


Code Description
P0977 SHIFT SOLENOID 2 CONTROL, HIGH
P0989 RETARDER PRESSURE SENSOR, FAILED LOW
P0990 RETARDER PRESSURE SENSOR, FAILED HIGH
P1739 INCORRECT LOW GEAR RATIO
P1891 THROTTLE POSITION SENSOR PWM SIGNAL, LOW
P1892 THROTTLE POSITION SENSOR PWM SIGNAL, HIGH
P2184 ENGINE COOLANT TEMPERATURE SENSOR, LOW
P2185 ENGINE COOLANT TEMPERATURE SENSOR, HIGH
P2637 TORQUE MANAGEMENT FEEDBACK SIGNAL (SEM)
P2641 TORQUE MANAGEMENT FEEDBACK SIGNAL (LRTP)
P2670 ACTUATOR SUPPLY VOLTAGE 2 (HSD2), LOW
P2671 ACTUATOR SUPPLY VOLTAGE 2 (HSD2), HIGH
P2685 ACTUATOR SUPPLY VOLTAGE 3 (HSD3), LOW
P2686 ACTUATOR SUPPLY VOLTAGE 3 (HSD3), HIGH
P2714 PRESSURE CONTROL SOLENOID 4, STUCk OFF
P2715 PRESSURE CONTROL SOLENOID 4, STUCk ON
P2718 PRESSURE CONTROL SOLENOID 4 CONTROL, OPEN
P2720 PRESSURE CONTROL SOLENOID 4 CONTROL, LOW
P2721 PRESSURE CONTROL SOLENOID 4 CONTROL, HIGH
P2723 PRESSURE CONTROL SOLENOID 1, STUCk OFF
P2724 PRESSURE CONTROL SOLENOID 1, STUCk ON
P2727 PRESSURE CONTROL SOLENOID 1 CONTROL, OPEN
P2729 PRESSURE CONTROL SOLENOID 1 CONTROL, LOW
P2730 PRESSURE CONTROL SOLENOID 1 CONTROL, HIGH
P2736 PRESSURE CONTROL SOLENOID 5 CONTROL, OPEN
P2738 PRESSURE CONTROL SOLENOID 5 CONTROL, LOW
P2739 PRESSURE CONTROL SOLENOID 5 CONTROL, HIGH
P2740 RETARDER OIL TEMPERATURE, HOT
P2742 RETARDER OIL TEMPERATURE SENSOR, LOW
P2743 RETARDER OIL TEMPERATURE SENSOR, HIGH
P2761 TCC PCS CONTROL, OPEN
P2763 TCC PCS CONTROL, HIGH
P2764 TCC PCS CONTROL, LOW
P278A KICKDOWN INPUT, FAILED ON
P2793 GEAR SHIFT DIRECTION
P2808 PRESSURE CONTROL SOLENOID 6, STUCk OFF
P2809 PRESSURE CONTROL SOLENOID 6, STUCk ON
P2812 PRESSURE CONTROL SOLENOID 6 CONTROL, OPEN
P2814 PRESSURE CONTROL SOLENOID 6 CONTROL, LOW
P2815 PRESSURE CONTROL SOLENOID 6 CONTROL, HIGH
U0001 HIGH SPEED CAN BUS RESET COUNTER OVERRUN (IESCAN)
U0010 CAN BUS RESET COUNTER OVERRUN
U0100 LOST COMMUNICATION WITH ECM/PCM (J1587)
U0103 LOST COMMUNICATION WITH GEAR SHIFT MODULE(SHIFT SELECTOR) 1
U0115 LOST COMMUNICATION WITH ECM
U0291 LOST COMMUNICATION WITH GEAR SHIFT MODULE(SHIFT SELECTOR) 2
U0304 INCOMPATIBLE GEAR SHIFT MODULE 1 (SHIFT SELECTOR ID)
U0333 INCOMPATIBLE GEAR SHIFT MODULE 2 (SHIFT SELECTOR ID)
U0404 INVALID DATA RECEIVED FROM GEAR SHIFT MODULE(SHIFT SELECTOR) 1
U0592 INVALID DATA RECEIVED FROM GEAR SHIFT MODULE(SHIFT SELECTOR) 2

How To Read Allison Transmission Codes

How-To-Read-Allison-Transmission-Codes

It just takes a little practice and to recognize which fault code system your vehicle has. For example for Allison transmissions there will be vehicles with a single digit entry for their fault codes.

For other vehicles, there will be a double digit readout and that should be easier to read. One thing to take note, we mentioned the letter D before but that seems to only stand for diagnostic come.

It will appear on both the single and double digit readouts in the first position. The reason for this is this code is telling you where in the fault code line up its position is.

For example if you see D then a 1 in the second box of the single digit readout, you are being told this is the first code in the line of codes that has been set. In the double digit readout this code should read D1 but with the D above the 1.

D2 followed by the code will tell you that it is the second code that has been set by the problem. To read the single digit code, and the readout may be vertical in your vehicle, you will see D1 13 12.

The first two digits are for the position of the code, first , second, third, and so on. The 13 tells you the main code and the 12 will tell you the sub code. In this example the problem is caused by ECU Input Voltage Low.

For the double digit code, you will see the D1 (or 2, etc). then the letter P (or C or U) by itself, then a pair of numbers vertically,, for example 07 then another pair of numbers 22 vertically.

That code would look like this- D1 P0722 and to find the meaning of this code you just look up P0722 which stands for- Output Speed Sensor, No Signal. That is how you read this code system.

Just be careful about the position of the numbers. They will go according to how your read out is set up in your vehicle.

How To Reset Allison Transmission Fault Codes

How-To-Reset-Allison-Transmissio-nFault-Codes

One way to do this., and there may be more than one depending on your Allison transmission model, you simply press the ‘Mode’ button and hold it. Keep holding it till you hear 2 beeps and then release the ‘Mode’ button.

Or if you have an older Allison transmission, the way to reset the transmission is to disconnect the battery cables for 30 seconds. This should clear all codes and give you a new start. You may have to clear the ECU as well and that only takes 10 seconds with the cables off.

If you own a newer Allison transmission, you may be restricted to using a code reader to reset the codes. It seems that a standard code reader you can get from the auto parts outlets will do the job here.

Just connect the reader to your diagnostic part of the transmission and then push the clear codes buttons.

Clearing Allison Transmission Codes

Clearing-Allison-Transmission-Codes

There are two sets of instructions. One is for the single digit readout and the other is for the double digit model. First the single digit read out:

1. Press and hold the ‘mode’ button for 3 seconds. The LED indicator light should start to flash. Release the mode button and the active codes should not be illuminated.

To clear inactive codes, you simply press and hold the ‘Mode’ button for 10 seconds. Some codes require engine cycling to clear and others are self-clearing.

2. Record all fault codes before you clear them. This will help your repair work go smoother.

3. Drive your vehicle around a little bit to see if any of the fault codes you cleared return or not. If they do return then take your vehicle to an authorized Allison transmission expert and have them fix the problem.

For the double digit display #2 and 3 are the same. It is just #1 that is different.

1. This step is very simple, just press the ‘Mode’ button for 10 seconds and both the active and inactive codes will be cleared.

That is all you have to do for the Allison 3000 and 4000 transmission series.

Some Additional Words

Now that you have the Allison transmission codes, you should be able to talk intelligently with the transmission repair man and understand what is wrong with this valuable part.

Also, with the right code reader you should be able to make your own diagnosis and see if you are able to make the repair yourself or not. Information is always king and when you have it, you are not at the mercy of the unethical repairmen.

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