Question about 2002 Nissan Quest
P0138 - Oxygen Sensor Circuit High Voltage (Bank1, Sensor2)
P0139 - Oxygen Sensor Circuit Slow Response (Bank1, Sensor2)
The Heated Oxygen Sensor (1 or 2) located rear of catalytic converter produces an output signal relative to oxygen storage capacity of catalytic converter. Ho2S 2 signal is less active than signal produced by front oxygen sensor. This code sets when HO2 Sensor voltage is greater than 999 mV for more than 2 minutes (time depends on model. Could be as high as 4 minutes)
Symptoms: There may be no noticeable symptoms except for MIL illumination. Possible high fuel pressure can over rich the system.
Causes: A code P0138 may mean that one or more of the following has happened:
* Faulty O2 sensor
* Short to battery voltage in O2 sensor signal circuit
* High fuel pressure (not as likely)
Here are some potential solutions:
* Replace O2 sensor
* Repair short to battery voltage in o2 sensor signal circuit
Hope helps (remember to rate this answer).
Posted on Oct 11, 2010
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