P0138 - Oxygen Sensor Circuit High Voltage (Bank 1 Sensor 2)
Fault codes never say to replace parts. They only indicate the circuit or system that needs further diagnosis. The only way to set this code is to have a break in the sensor's ground wire or the signal voltage wire is shorted to the 12 volt heater wire for that sensor. Start by looking for a corroded terminal in the sensor's connector or a terminal that got stretched or pushed out of the plug body. Next, check the wiring harness for signs of melted wires, especially where they travel near hot exhaust parts.
If you haven't found the cause by this time, use a scanner to view live data and look at the sensor's voltage compared to the passenger side sensor. If it's normal, you have an intermittent problem that isn't currently acting up. Try flexing on the wire harness to see if the voltage changes. If the voltage IS high, unplug connectors going to that sensor and wiggle harnesses until the voltage changes. That will help you narrow down the location of the problem.
Tuesday, April 30th, 2013 AT 2:38 PM