U0909 Code:

OBD-II Diagnostic Network (U) Trouble Code

Possible Cause

The most common causes of this U0909 code being stored are due to a defective input speed sensor or output speed sensor. Other common causes include shorted, open, corroded, or damaged wiring circuits or connectors.

Common Symptoms

  1. It can accurately diagnose computer and circuitry problems by monitoring vehicle operation while the vehicle is being operated
  2. Look for shorted or burned wiring and replace circuitry and connectors as required
  3. Typical causes of low pump pressure include clogged hydraulic passages, a defective pump, faulty shift solenoids, or a faulty electronic pressure regulator
  4. To perform a thorough diagnosis, any transmission leaks should be repaired and the transmission should be filled with the proper amount and type of fluid (if the fluid smells really "burnt" and you are experienced enough to detect it, you may go ahead and condemn the transmission)

Similar Problems

IC Module 4X Ref Circuit Intermittent, No Pulses
Control Module Throttle Actuator Position Performance
TFP Valve Position Switch-Drive Without Drive Ratio

U0909 Troubleshooting

A sure sign of this is smoke or steam being emitted from underneath the hood. The ignition timing could be set incorrectly and will require adjustment. If, when looking under the hood, you notice that the drive belts appear loose, they need to be tightened or completely replaced. If there is a noticeable pool of fluid underneath the car, this could be a sign of the cylinder head gasket failing. That will be confirmed in the form of billowing smoke being blown from the exhaust system. U0909 OBD2 may also be triggered by faults earlier down the line. For example, a dirty MAF sensor might be causing the car to overcompensate in its fuel-trim adjustments. As a result, oxygen sensors are likely to report fuel mixture problems.

How to turn off U0909 check engine light ?

There are two ways to turn off the check engine light:

A repair technician can do so once repairs have been made.
The OBD II can automatically turn it off when it fails to detect the problem after several diagnostic cycles.

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