DTC P0131: Heated Oxygen Sensor Bank No. 1 (Left Bank), Sensor No. 1 (B1 S1) Circuit, Low Input: Condition

WARNING: This page is about a different car, the 2002 Suzuki Grand Vitara. However, it is still accessible from the selected car via links, so may be relevant.

DTC is set when Heated Oxygen Sensor (HO2S) Bank 1, Sensor 1 maximum output voltage is 0.4 volt or less. MIL is illuminated when ECM (PCM) detects malfunction during 2 consecutive drive cycles. Possible causes are:

HO2S Bank 1, Sensor 1 malfunction.
Fuel injector malfunction.
Fuel pressure control system malfunction.
ECM (PCM) malfunction.
Low fuel level.