Code P0138

KKIRBYROCKS

MEMBER
2004 KIA RIO

4 cyl 105000 miles

this evening my check engine light came on-I took it to autozone and 4 things came up as a possibility for this code-rich air/fuel ratio, blocked exhaust system, restricted air intake system-plugged filter or faulty ho2s-the car is not loud so I don't think it would be the exhaust-what can it be?

1 Reply

RASMATAZ

MECHANIC
75,992 POSTS

P0138 OBD-II Trouble Code
Technical DescriptionO2 Oxygen Sensor Circuit High Voltage (Bank1, Sensor2)

What does that mean?The Heated Oxygen Sensor (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)

SymptomsThere may be no noticeable symptoms except for MIL illumination. Possible high fuel pressure can over rich the system.

CausesA 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)
Possible SolutionsHere are some potential solutions:

Replace O2 sensor
Repair short to battery voltage in o2 sensor signal circuit