ALLISON TRANSMISSION Common Error Codes

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Most common transmission error codes

If the Check Engine light turns on, there are a number of reasons that could turn it on. Many are gearbox related. Our company provides an on-site computer diagnostics service that will identify problems that can cause the appearance of Check Engine in the form of alphanumeric codes, known as P-codes. The most common P error codes are listed below:

P0218 code: Transmission overheating

Your transmission is overheating. Some vehicles have an instrument light that will say “trans over temp”, but not all vehicles have this feature. This code can mean that the fluid temperature sensor needs to be replaced or something with the wiring, but the problem can be much more complex, especially if there are other P-codes.

P0613 code: TCM processor error

You don't have to worry too much about this error code - it just tells you that there is an internal error inside the transmission control module (TCM). This is a programming problem. Have your dealer replace the TCM.

P0614 code: ECM / TCM incompatible

This is another purely informational code that tells you the ECM and TCM are not communicated. If you have this code, it is most likely that this or that unit was recently replaced, and if you installed a used part, it is not configured to work with the new part. On newer vehicles, these parts are programmed to work with only one specific vehicle and cannot be programmed to work with another.

P0700 code: transmission control system malfunction

Again, this is an informational code. In most vehicles, the TCM is the only computer that can turn on the check engine light. If there is a problem preventing the indicator from turning on, you will see this code.

P0706 code: Transmission range / performance sensor circuit malfunction

The gear range sensor tells the TCM the position of the gear lever. It also contains a neutral safety switch, which ensures that you can start your car when the automatic transmission is only in neutral or in a parking lot. This code could indicate corrosion or other problems in the gear range sensor.

P0715 code: Transmission input speed sensor malfunction

Your automatic transmission uses input and output speed sensors to determine if your gear is in the gear that the transmission control module (TCM) wants to transmit. If you see this code, it means that the TCM is not calculating the template offset incorrectly. Usually you will find that the transmission goes into "limp" mode if this happens. A damaged connector or a wiring problem could be the problem, and the usual solution is to replace the input speed sensor.

P0720 code: transmission output speed sensor malfunction - circuit malfunction

Speed sensors tell you how fast your output or input shaft is moving. If the TCM is unable to read this information, your speedometer will not accurately indicate your speed. It may be necessary to replace the output speed sensor, there may also be a poor contact in the connector or a defect in the wiring harness, as well as in the automatic transmission ECU.

Error P0729 P0730 P0731 P0732 P0733 P0134 P0735 P0736

These codes report gear ratio problems. The only difference in these transmission trouble codes is the mechanism that is being identified. They all report the same error, but report it for different transmissions. The TCM input and output sensors measure the speed of the input and output shafts, and if they are not moving at the correct speed, you will receive transmission error codes. Most of the time, the problem is as simple as low transmission fluid, although it can also indicate problems with the torque converter clutch or shift solenoid in combination with other P-codes.

The torque converter converts engine rpm into twisting force to drive your vehicle and provides additional gear ratio when driving at highway speeds. The solenoid adjusts the torque converter clutch and if you see this P code it could mean the solenoid is corroded or otherwise damaged. If this is not the case, then there may be a problem in the wiring around the solenoid.

Error P0750-P0770

All of these codes are related to a failure of the shift solenoid. Your TCM tells your gear how and when to change by opening one of these solenoids so that the transmission fluid is transferred to the transmission hydraulic control section for that gear. If one shift solenoid fails, the mechanism it is designed to control will not work properly, if at all. You will also see other P-codes along with them.

These are the most common transmission trouble codes. As soon as the mechanic completes the computer diagnostics of the car, he will be able to tell you what repairs are needed.