- May 9, 2023/
- RV Transmission/
- ByJames V.
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
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
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
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.