General Information

P0157 O2 Sensor Circuit Low Voltage (Bank 2 / Sensor 2)

General Information

Component Location





General Description

The rear heated oxygen sensor is mounted on the rear side of the Catalytic Converter (warm-up catalytic converter) or in the rear exhaust pipe, which is able to detect catalyst efficiency. The rear heated oxygen sensor (HO2S) produces a voltage between 0V and 1 V. This rear heated oxygen sensor is used to estimate the oxygen storage capability. If a catalyst has good conversion properties, the oxygen fluctuations are smoothed by the oxygen storage capacity of the catalyst. If the conversion provided by the catalyst is low due to aging, poisoning or misfiring, then the oxygen fluctuations are similar to signals from the front oxygen sensor.

DTC Description

Checking output signals from HO2S under detecting condition, if an output signal is below specified value for more than predeterminate time, PCM sets P0157.

DTC Detecting Condition





Specification





Diagnostic Circuit Diagram





Signal Waveform & Data












Fig.1) Normal waveforms of upstream HO2S (the upper) and downstream HO2S (the lower) (chassis ground used)
Fig.2) Normal waveforms of upstream HO2S (the upper) and downstream HO2S (the lower) (sensor ground used)
Fig.3) Normal graph of upstream HO2S and downstream HO2S at idle.

After warming-up, if accelerator pedal is released suddenly around 4000 rpm, the HO2S signal reading will be lower than 200 mV resulting from Fuel cut-off for the moment. Conversely, if suddenly accelerator pedal is depressed, HO2S signal reading will be around 0.6 V ~ 1.0 V. At idle, Normally HO2S signal will switch from lean to rich with 3 Hz. And as racing, Its frequency rises.