P0038 indicates that the engine computer has detected an abnormally high voltage in the heater circuit for the downstream oxygen sensor on bank 1. This usually points to a short to power or a lack of ground in the heater circuit, preventing the sensor from warming up properly.
The internal heater element of the Bank 1 Sensor 2 oxygen sensor has shorted or failed.
Chafed or damaged wiring in the heater circuit is contacting a power source, causing high voltage.
A corroded, loose, or broken ground connection for the heater circuit causes voltage to back up and read high.
Corroded, pushed, or spread pins in the sensor connector are causing a cross-circuit or high resistance condition.
An internal driver failure within the engine computer is keeping the circuit powered, though this is highly uncommon.
Yes, you can usually drive safely as this downstream sensor monitors catalyst efficiency rather than controlling the air-fuel ratio, but you should repair it to pass emissions tests.
No, replacing the PCM is almost never the correct fix for P0038. Mechanics commonly warn against this because the vast majority of the time, the cause is a failed sensor or a wiring issue, not the computer.
Bank 1 refers to the side of the engine that contains cylinder #1, and Sensor 2 is the downstream oxygen sensor located after the catalytic converter.
The heater warms the oxygen sensor up to operating temperature quickly after a cold start, allowing the engine computer to enter closed-loop fuel control sooner for better efficiency and lower emissions.