Signs of a malfunctioning TCM
A malfunctioning Allison 29561675 TCM can present several clear signs that indicate it may need replacement. Recognizing these symptoms early on can help you avoid more extensive damage to your transmission and save on repair costs.
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Classic symptoms of a failing TCM
Common symptoms of a failing TCM include a lack of response from the shift pad, activation of limp mode, gear selection errors, and specific diagnostic trouble codes such as 6927 and 3513. These issues often indicate that the TCM is no longer effectively managing the transmission.
No response from the shift pad
If the shift pad in your vehicle becomes unresponsive, or you experience inconsistent shifts when attempting to change gears, this is a strong indicator that the TCM may be failing. Since the TCM controls communication with the shift pad, a malfunction can cause these issues.
Limp mode and warning lights
Another sign of a failing TCM is when the vehicle enters limp mode—where the transmission is locked into one gear to protect the system from further damage. You may also notice warning lights on your dashboard, such as the Check Engine light, which signals that there’s an issue with the TCM or related components.
Gear selection errors and diagnostic codes
Gear selection errors, such as being stuck in one gear or not being able to shift into the desired gear, may also point to a faulty TCM. Diagnostic trouble codes like 6927 and 3513 are associated with transmission control problems and can sometimes be read using an OBD-II scanner. You can also use your Allison shift pad to check codes. Call Reaction Force so we can walk you through how to check for codes using the shift pad. If you see these codes, the TCM should be checked and possibly replaced.