P2789 code definition
When the P2789 code applies to vehicles with dual clutch automated manual transmissions. When it is saved, it indicates that the powertrain control module (PCM) has detected an abnormality in the clutch’s adaptive learning system and that some error has occurred in the clutch system’s adaptive learning capabilities.
What the P2789 code means
To adapt to the vehicle owner’s style of driving, the dual clutch system, controlled by the vehicle’s computer, learns and adapts, thanks to input from a number of actuators and sensors. When the clutch adaptive learning system is unable to continue to learn and adapt, the P2789 code is saved, alerting the driver through an illuminated Check Engine Light or MIL (Malfunction Indicator Light), that the clutch adaptive learning system is not performing normally.
What causes the P2789 code?
The P2789 code is caused when the desired normal amount of adaptive response exceeds its predetermined limit. Depending upon the make and model of the vehicle, the P2789 code may not be stored until several failure cycles have occurred, but after this the code will be stored and the MIL or Check Engine Light will illuminate.
What are the symptoms of the P2789 code?
There may be no noticeable symptoms besides the illuminated MIL. This symptom, however, may also come alongside others, including:
- Engine stall when the vehicle comes to a complete stop
- Hard shifting
- Clutch and/or transmission slippage
- Lowered fuel efficiency
- Transmission overheating
- Failure of the clutch to engage or disengage
Other codes may also accompany the P2789 code, including DTC codes for:
- Gear ratio slippage
- Torque converter clutch
- Transmission slippage
- Clutch lock up
How does a mechanic diagnose the P2789 code?
To diagnose a P2789 code, a mechanic will use a code reader (or scanner) and a digital volt/ohmmeter. Upon scanning for Diagnostic Trouble Codes, other codes related to the clutch and transmission system should be diagnosed and fixed first, as one or more of these may be the cause of the P2789 code.
Mechanical clutch failure is a common cause of the P2789 code. So, after checking for other codes, the mechanic will diagnose and repair any defective solenoids, sensors, and/or actuators. The mechanic will also take steps to check for insufficient fluid pressure, as well as transmission diagnostics.
Common mistakes when diagnosing the P2789 code
The most common mistakes when diagnosing the P2789 code generally involve overlooking malfunctions in the shift solenoid, pressure control solenoid, and/or wiring. When these are missed, a clutch or transmission replacement or rebuild is often done when it is not called for, costing the vehicle owner more while failing to solve the problem.
How serious is the P2789 code?
While some instances of the P2789 code come with no symptoms at all, this is a serious problem that can get worse if left undiagnosed. Hard shifts, a clutch that will not disengage or engage, and/or an engine that stalls at idle can put the driver in significant danger, depending on where and when these malfunctions happen.
What repairs can fix the P2789 code?
Some common repairs for the P2789 code include:
- Repairing or replacing system circuits and/or connectors
- Repairing or replacing the electrical pressure control solenoid, and/or shift solenoid.
A test must be done after each repair to determine whether or not the mechanic has found the cause of the P2789 code.
Additional comments for consideration regarding the P2789 code
Failure to continue to learn and adapt to your driving style may not seem like a major problem, but considering how many other issues can be triggered by the P2789 code and codes associated with it, it is definitely not one to leave alone. An undiagnosed P2789 code problem could put you in serious danger and could cause other problems for your transmission and clutch. If you’ve experienced one or more of the symptoms of this code and your MIL or Check Engine light has illuminated, you should get it diagnosed and repaired immediately.
Need help with a P2789 code?
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