One of the better aspects of error codes is that they do tend to help more than they frustrate. Once you know what and where the problem is, the issue is easier to fix and sometimes faster to get it done.
The P0880 Allison transmission error code stands for Transmission control module (TCM) -power input signal malfunction. What that means is that it lost power along the drive and a part may need to be replaced or wires need to be checked.
To learn more about this fault code, just continue to read our article. It has the information you need to know so you do not panic when you see the code illuminated on your dash. Take a few minutes to learn about this code.
The technical definition is as follows: “Transmission control module (TCM) -power input signal malfunction” the easier to understand definition goes like this:
“it means that the PCM has detected a malfunction in the power (voltage) input signal circuit for the transmission control module (TCM).” (source)
To set this code, the PCM does a self-inspection on its circuits and power supply, etc. If there is a problem, the code is triggered or stored. You should see the Check engine light illuminated on your dash.
The reason this stored code is important is that some models of vehicles can go into limp mode when it is triggered. Not every model will enter this mode and some owners have experienced no problems once they shut their vehicle down and restarted it to drive later on.
The sources you should check first are any wiring and connections to make sure they are in top shape, not loose, and soon. Another possible source will be the TCM. Have that checked by a top transmission technician.
If the TCM is the problem, then look at the shift solenoid to see if that is working fine. If you do not handle this problem quickly, you can experience other transmission issues and heftier repair bills.
When you see this code on your screen or the check engine light has been illuminated, then you should experience some of the following symptoms. These symptoms may pop up before you see the code:
- Harsh or erratic shifting
- Engine may stall at idle
- Delayed transmission engagement
- Shift interlock function may be disabled
- Intermittent or total speedometer/odometer failure
- Other transmission control codes are likely
The possible sources for these problems and this code will be including the following items:
- Defective PCM or TCM power relay
- Blown or corroded fuse
- Burnt fusible link
- Shorted or open TCM power input circuit
- Bad TCM/PCM or programming error
These issues may be above your transmission skill set so make sure to have a qualified Allison transmission repairman check your transmission out for you. To troubleshoot this error code you will need a diagnostic scanner for sure.
You will also need a DVOM or a digital volt/ ohm meter and vehicle information. That is just to get you started. You may not have all the tools available where you are so going to a transmission expert is the best advice possible.
Before you do that, you can start checking the fuses and fusible links to make sure those have not blown or become disconnected. You need to use the DVOM because some fuses will look okay. They may only show their inability to work when you put a load on them.
Your vehicle information manual should provide the location of the fuses and the fusible connections. If those are okay, then try swapping identical relays to check the TCM.
You can use the horn relay, starter relay, fuel pump relay, air conditioning clutch relay, and controller relays. These are similar enough in design to swap for diagnostic purposes.
This swap will help you diagnose the TCM relay and see if it is operating correctly. This is the quickest and easiest method to use to make a relay diagnosis, just make sure to put all the relays back in their original locations.
Do not forget to replace blown fuses and bad fusible connections.
The TCM’s duties include monitoring all the transmission settings and identifying the best one. It also manages different aspects of the transmission’s operation.
Now to make sure the transmission is shifting effectively, the PCM analyzes voltage input signals. These signals come from the transmission input speed sensor and transmission output speed sensor.
If there is a problem, the PCM will trigger the P0880 code. Some people say this code will not initiate the limp mode but others say it eventually will. Here is the tricky part about this code.
It may not always show up as a P code. It may show up as B or a U code and which code is used will depend on the vehicle’s make and model. Everyone is saying that once you see this code in any version, the diagnosis and repair should be handled by trained transmission experts.
To do it yourself, you will need the proper tools and knowledge. If you do not have either one or both, then make sure you go to a transmission repairman who does. It is said that this repair can be tricky at times.
Error codes do help. They do indicate a real problem in your car’s systems most of the time. There are possibilities of you receiving a phantom error code which is why you need to take your vehicle to a trained mechanic.
Normally, they can spot the phantom code and clear it without too much trouble. With today’s modern engine and transmission designs, you may not have all the tools needed to make these repairs.
These tools can be expensive to buy. So make sure you have a trusted repairman nearby so you can get the problem solved inexpensively.