This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.
Transmission Control System MIL Request Circuit/Open
Since it involves the function of the transmission maintenance indicator light (MIL), this trouble code underscores the importance of using your OBDII scanner on a regular basis. A P0802 can save when any number of errors occur, and the underlying issue needs to be found and corrected quickly to prevent potential transmission damage.
Any anomaly in the transmission control system is going to save a code to both the transmission control module (TCM) and the power control module (PCM). Normally, your TCM will also illuminate the MIL, but trouble code P0802 saves if there is a problem in the circuit between the TCM, the MIL and the PCM. Essentially, the PCM is telling the rest of your vehicle’s electronic brain that the MIL isn’t working. There may not be an issue with the TCM or transmission itself, but you should definitely get your vehicle checked out to verify that the MIL is the only problem.
This trouble code only saves if there is a problem with the MIL. Generally, the bulb or LED for the MIL may need to be replaced, but there may also be an issue with the wiring or connectors causing the MIL failure.
There are a number of symptoms that accompany a P0802. Here are the primary issues you may notice while driving:
- No Check Engine Light even when the vehicle is experiencing drivability or normal operation issues
- The vehicle’s transmission is slipping or overheating
- The transmission struggles to shift between gears or won’t shift at all
- The engine stalls when the vehicle is stopped
Step by step troubleshooting is essential, but fortunately there are only a few steps to follow for diagnosing and repairing this trouble code.
Step one after reading codes should always be to visually examine the TCM wiring harness for any damage, corrosion or loose connectors.
Step two is test drive time. If you verified the wiring is in good shape, clear codes and take the vehicle for a quick spin to see if the code recurs.
Recurrence of a P0802 means that something in the circuit needs to be repaired or replaced and you should proceed accordingly.
There isn’t always a Check Engine Light when your vehicle codes a P0802, so it is important to scan for additional trouble codes when this one pops up. There may actually be an issue with your transmission, TCM or PCM that needs to be addressed, and the P0802 is just one indicator among many others.
How serious is this?
The answer to this question largely depends on what caused the PCM or TCM to illuminate the MIL in the first place. It can be just a minor issue like the consistency of your transmission fluid, but it could also be a far more serious problem with your transmission that needs immediate attention. Your technician should be able to advise you further once they complete their diagnosis and determine why the MIL was triggered in the first place.
What repairs can fix the code?
As the specific issue that causes this code relates only to the MIL, your repair technician should follow the troubleshooting steps to determine how to correct your MIL problem first. They will verify the code with an OBDII scanner, then repair or replace any wiring or connectors that are worn, corroded or damaged. They will also replace any burnt out or faulty MIL bulbs as well since they are the most common cause of a P0802.
In the grand scheme of your vehicle’s normal operation, a P0802 is a relatively minor code unless you are experiencing drivability issues with no check engine light. Your first instinct when you experience issues should always be to plug in an OBDII scanner and see what codes are saved in the system first.
Chances are the MIL isn’t the only malfunctioning component in your TCM or PCM, and because the transmission MIL won’t light up you won’t know about them until you run a scan. If you do pull a P0802 on your own, it is highly recommended you take your vehicle into a shop for a full diagnostic. An experienced technician may find and fix other underlying issues you wouldn’t know to look for on your own.
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