HO2S Heater Control Circuit Low (Bank 1 Sensor 1)
The engine computer sees a problem in the heater for the front oxygen sensor on bank 1. The heater helps the sensor warm up quickly so fuel control works correctly. A low heater circuit signal usually means a wiring, fuse, relay, or sensor problem.
The vehicle may still run, but fuel economy, emissions, and cold-start operation can suffer. Diagnose it soon because related wiring or sensor faults can get worse.
P0031 sets when the PCM detects a low voltage condition in the heated oxygen sensor heater control circuit for Bank 1 Sensor 1. This is the upstream sensor on the bank that contains cylinder 1. The fault can be caused by an open heater circuit, a short to ground, damaged wiring, blown fuse, bad relay, or a failed oxygen sensor heater element.
It is the upstream oxygen sensor on the side of the engine with cylinder 1.
Yes. If the sensor warms up slowly or not at all, fuel control can stay less accurate longer.
No. Wiring, fuse, relay, or PCM control problems can also cause this code.
You can clear it temporarily, but if the fault remains the check engine light will return and emissions may suffer.