The PCM expects the downstream (post‑catalyst) oxygen sensor on bank 2, sensor 2 to stay within a specific voltage range during deceleration when the engine is running lean. If the sensor signal goes outside those limits while the throttle is closed, the PCM sets P2379. This indicates the sensor is not responding correctly to the lean condition that occurs during decel.
The sensor itself may be degraded, contaminated, or have a failed heater circuit, causing its voltage to drift out of the expected range during decel.
Damaged, corroded, or loose harness connectors, shorts to ground, or open circuits can produce erratic sensor readings that trigger the code.
A leak in the exhaust manifold or pipe before the downstream O2 sensor allows extra oxygen to enter, skewing the sensor signal and making it appear out of range.
Leaking fuel injectors, a faulty fuel pressure regulator, or excessive fuel pressure can cause the mixture to be richer than expected when the throttle is closed, affecting sensor output.
While possible, a defective powertrain control module is rare for this code; it should only be considered after the sensor, wiring, exhaust, and fuel systems have been verified as good.
No. The powertrain control module is seldom the cause of this code; it should be considered only after the oxygen sensor, its wiring, exhaust leaks, and fuel system have been checked and ruled out.
A failing converter usually affects upstream O2 sensor readings; it is less likely to cause a downstream sensor out‑of‑range during decel, but a severely degraded converter can contribute to abnormal sensor behavior.
Clearing the code only turns off the Check Engine Light; if the underlying issue is not repaired, the code will likely return once the PCM monitors the sensor again.