with possible causes and some tech notes.
How does a mechanic diagnose the P0138 code?
Scans codes and documents freeze frame data and then clears codes to verify failure.
Monitors O2 sensor data to see if the voltage is switching back and forth between low and high at a fast rate compared to other sensors.
Checks the O2 sensor wiring and the harness connections for any corrosion in the connections.
Checks the O2 sensor for any physical damage or fluid contamination.
Checks for exhaust leaks before the sensor.
Follows the manufacturer's specific pinpoint tests for further diagnosis.
Common mistakes when diagnosing the P0138 code
Follow these simple guidelines to prevent misdiagnosis:
O2 sensor 1 for bank 1 can be used to diagnose O2 sensor 2 for bank 1 by looking at both sensors operation for comparison. The operation should be nearly the same, except sensor 2 should have a lower O2 reading since the catalyst should burn off the excess fuel and oxygen.
Check the O2 sensor for oil or coolant contaminants from any engine leaks.
Check the catalyst for damage or it being clogged that can cause erratic sensor readings.
How serious is the P0138 code?
The voltage output from the O2 sensor may be due to the exhaust catalyst being broken apart, which can cause the O2 sensors to give high output voltages.
The ECM may not control the fuel-to-air ratio of the engine properly, leading to a clogged catalyst and excessive carbon buildup in the engine with fouled spark plugs.
What repairs can fix the P0138 code?
Replacing the O2 sensor for bank 1 sensor 2
Repairing or replacing the wiring or connection to the O2 sensor for bank 1 sensor 2
Replacing the catalyst in front of the sensor
Repairing a leaking injector
Start with this information. The traction control problem is something different. There should be error codes for that too with the proper scanner. The rear wheel sensors and wiring connections for the rear wheel sensors are know to have problems in the 2009 and 2010 model Vibes. The sensors can also get rusted over or a bad wheel bearing can cause the sensor not to read the wheel speed. Then again it could be something else too.