code readers on 2000 Nissan Altima

I used a diagnostic code reader and came up with two codes, P1126 and P0138, can you tell me what stand for?

1 answer
The trouble code data is listed below. I would start by replacing the engine coolant thermostat, and checking the O2 sensor heater element for the sensor listed. (Front Sensor, Bank 2)
Trouble Code Conditions:
DTC P0115 not set, engine started, IAT sensor more than 14°F and ECT sensor from 14-149°F at engine startup, engine runtime over 10 minutes, and the PCM detected that the engine temperature did not reach at least 176°F under these conditions.
Possible Causes:
* Inspect for low coolant level
* Inspect for incorrect coolant mixture
* Check the operation of the thermostat (it may be stuck open)

Trouble Code: P0138 2.4L L4
HO2S-12 (Bank 1 Sensor 2) Circuit High Input (Rich Shift)
Trouble Code Conditions:
Engine started, vehicle driven to a speed over 20 mph for 1 minute, IAT sensor from 14-122°F, fuel level over 25%, and the PCM detected the HO2S signal did not reach the maximum voltage level of 0.60v, or the signal remained at more than 600 mv in the test.
Possible Causes:
* Fuel pressure regulator leaking or fuel injectors leaking
* HO2S may be contaminated or it has failed
* HO2S heater is damaged or has failed
* PCM has failed
* TSB 01-016 (9/01) contains information related to this code