U3239 Code:

OBD-II Diagnostic Network (U) Trouble Code

Possible Cause

Possible causes of U3239 include a faulty oxygen sensor, faulty electrical connector at the oxygen sensor, faulty or shorted wiring in the oxygen sensor circuit, a blown fuse for the oxygen sensor (if applicable), low or excessive fuel pressure, a vacuum leak on the engine, excessive exhaust leaks, or a faulty PCM.

Common Symptoms

  1. After the codes are cleared, operate the vehicle to see if the code returns
  2. Engine and transmission ground cables, straps, and wires are sometimes left dangling after repairs are performed
  3. Some applications also utilize the inlet door to regulate air flow through the intake tube by adjusting the degree to which the door opens according to throttle position
  4. There are several tools which will be instrumental in attempting to successfully diagnose the conditions which contribute to this code being stored

Similar Problems

Fuel And Air Metering
Crankshaft Position Sensor Circuit Performance
TFP Valve Position Switch-Drive Without Drive Ratio

U3239 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. Parts or components should not be replaced with reference to only a U3239 DTC. The vehicle service manual should be consulted for more information on possible causes of the fault, along with required testing.

How to turn off U3239 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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