What is nissan quest code p0138/p0139 - 2002 Nissan Quest

No code tells you to replace a part , need to do diagnostic's for said code .
P0141 - O2 Heater Circuit (Bank 1, Sensor 2) Description: See the description for DTC P0135. Possible Causes: See the possible causes for DTC P0135. Diagnostic Aids: See the diagnostic aids for DTC P0135. Application Key On Engine Off Key On Engine Running Continuous Memory All GO to Pinpoint Test DW .
DW: Heated Oxygen Sensor (HO2S) DW: Introduction DW1 CHECK FOR DIAGNOSTIC TROUBLE CODES (DTCS) Are DTCs P0040, P0041, P0053, P0054, P0055, P0059, P0060, P0132, P0133, P0135, P0138, P0139, P0141, P0144, P0147, P0152, P0153, P0155, P0158, P0159, P0161, or P1127 present?
Yes No For DTCs P0040 or P0041, GO to DW2 .

For DTCs P0053, P0054, P0055, P0059 or P0060, GO to DW14 .

For DTCs P0132, P0138, P0144, P0152 or P0158, GO to DW20 .

For DTCs P0133 or P0153, GO to DW3 .

For DTCs P0135, P0139, P0141, P0147, P0155, P0159 or P0161, GO to DW9 .

For DTC P1127, GO to DW19 . For all others, GO to Section 4, Diagnostic Trouble Code (DTC) Charts and Descriptions .
DW9 DTCS P0135, P0139, P0141, P0147, P0155, P0159 OR P0161: CHECK FOR A SOURCE OF POTENTIAL HO2S CONTAMINATION

• Investigate the following items as potential sources of HO2S contamination:
  • use of unapproved silicon sealers
  • fuel contaminated by silicon additives
  • excessive oil consumption
  • glycol leaking internally in the engine
  • lead-contaminated fuel
  • short drive cycles in cold weather
  • use of unapproved cleaning agents

Is a concern present?
Yes No REPAIR the source of the contamination.

CHANGE the engine oil and oil filter.

RESET the keep alive memory (KAM). REFER to Section 2, Resetting The Keep Alive Memory (KAM) .

REPEAT the self-test. GO to DW10 .

Bank 1 by precat look for cylinder one that side is bank one

P0138 O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)
P0139 O2 Sensor Circuit Slow Response (Bank 1 Sensor 2)
P0325 Knock Sensor 1 Circuit (Bank 1 or Single Sensor) -Circuit Malfunction
think you just need a new o2 sensor

P0138 O2 Sensor Circuit High Voltage
P0139 O2 Sensor Circuit Slow Response
P0420 Catalyst System Efficiency Below Threshold

First things to check and clean is the MAF sensor and the IAC valve...these two cause problems from carbon and dirt buildup...use MAF cleaner only....if this works, great, if not....

Clean trottle body....or

Check for a plugged catalytic converter...remove the O2 sensors and start the car, does it seem better? If it does change the catalyst..

Po 136 ---is an oxygen sensor code for a sensor
on Bank #1 Sensor #2

Nothing to do with MAF

Also education & solutions can be for using Google

Put in------ OBD2 Codes PO138 nissan sentra

Hi, guys. you can read this article first. Why check engine light is on. Maybe it is able to help you. Good luck.

P0138- o2 circuit high voltage, bank 1 sensor 2
P0129- 02 circuit slow response Bank 1 sensor 2
rear o2 sensor weak, replace it, will be the one after the caliltice converter.

Possible mass airflow sensor. A cheaper way to get around paying for the super expensive 2001 Path part is to use the same year maxima sensor since they use the same motor :)

This code indicates the oxygen sensor on bank one is not operating properly. Check the wiring to this sensor for breaks or grounding before replacing the sensor.

I would say that your o2 sensors are faulty either the pre or the post . They must be intermitten so I would replace both