The input turbine speed sensor detects rotation of the input shaft of the input shaft speed sensor transmission. The computer uses that information, along with the output shaft speed sensor to determine if the transmission is operating according to plan. If the computer detects a difference between the input shaft speed , and the expected output shaft speed, it will adjust transmission pump pressure to prevent clutch disc slip. If adding pressure doesn't solve the problem, it will set a trouble code.
Circuit High Input codes like U3821 are mostly caused by defective alternators that develop excessive voltages, although there may be other causes as well, such as short circuits that 'leak' current into a particular system from other, unrelated systems that work on higher voltages. Note that in the case of short circuits that leak power into a control circuit, there is likely to be other, seemingly unrelated trouble codes present along with the code(s) being investigated. Diagnosing a 'high input' code will always involve a thorough testing of the charging system as a first step, followed by measures to isolate the system from all other possible sources of power during resistance, continuity, and reference voltage tests.
When you turn on the ignition, the Service Engine Soon or Check Engine U3821 light should flash briefly, indicating that the OBD system is ready to scan your vehicle for any malfunctions. After this brief flash, the light should stay off while you drive as long as no problems are detected. If overdrive band failed off so, you'll be glad to know that your vehicle is equipped with an early warning system that could save you time, money, and fuel in addition to helping protect the overdrive band failed off.
Difficulty Level (Easy)
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Repair Time (45 Min.)
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Cost Prediction : $ 75-90 |
U3821 is a kind of Network Trouble Code
U-code indicates that engine communication errors and shows lost communication with engine parts.U-Codes are fairly straight forward, given all of the articles and technical publications that have been written regarding these problematic codes. In most cases, it just comes down to identifying the module that isn't communicating with the other modules on the CAN bus line for whatever reason. |
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