P0156

Diagnostic Chart:

Schematic:

The rear Heated Oxygen Sensors (HO2S) are used to determine the oxygen storage capability of the pup converter. Rear O2 diagnostics will run after the sensor has been active for more than 80 seconds, and the catalyst temperature is greater than 600°C (1112°F). The ECM will set this DTC when the signal being received is lower than expected.

DTC PARAMETERS
This DTC will set when:
^ The sensor signal voltage less than 0.40 volts for longer than 80 seconds.
^ Rear oxygen sensor sensor is closed loop
^ No EVAP codes set
^ Fuel tank is not empty
^ Catalytic temperature less than 700°C (1292°F)
^ Battery voltage greater than 11.03 volts

DTC P0156 is a (type B) DTC

DIAGNOSTIC AIDS
To locate an intermittent problem use Scan tool to monitor HO2S Bank 2 Sensor 2 voltage with engine idling at normal operating temperature.

Wiggling wires while monitoring HO2S Bank 2 Sensor 2 voltage may locate area where a short to ground exists.

If a HO2S bank 2 sensor 1 DTC is also set diagnose it first. A failed HO2S bank 2 sensor 1 may create a lean engine running condition which set the HO2S bank 2 sensor 2 DTC.

Review failure record information to check if vehicle was running lean in power enrichment (TP angle greater than 75%, HO2S Bank 2 Sensor 1 greater than 1.2) when the DTC was set. If so, check for a possible lean condition.