P0158

Diagnostic Chart:

Wiring Diagram:

Circuit Description
The VCM supplies a voltage of about 0.45V (450 mV) between the HO2S High and the HO2S Low circuits. (If measured with a 10 megohm digital voltmeter, this may read as low as 0.32V.) The HO2S varies the voltage within a range of between about 1 V (1000 mV) if the exhaust is rich, to about 0.10 V (100 mV) if the exhaust is lean.

The sensor is like an open circuit and produces no voltage when it is below about 360°C (600°F). DTC P0158, P0158 or an open sensor circuit or cold sensor causes Open Loop operation. P0152 determines if the HO2S or circuit is shorted to high by checking for a rich condition during steady throttle. DTC P0158 is a type A DTC.

Conditions for Setting the DTC

^ No Throttle Position (TP) sensor DTCs
^ No EVAP DTCs
^ No IAT sensor DTCs
^ No MAP sensor DTCs
^ No ECT sensor DTCs
^ No MAF sensor DTCs
^ No intrusive test in progress
^ No device controls active
^ System voltage is at least 9V

Test Enable Rich Test

^ Closed Loop
^ Air/fuel ratio is at least 14.5 but less than 14.8
^ TP is greater than 0% but less than 50% Above met for 5 seconds
^ HO2S (Bank 2 Sensor 2) DTCs not active since code clear
^ HO2S (Bank 2 Sensor 2) voltage is greater than (993 mV) 0.993V.

Test Enable Decel Fuel Cut Off (DFCO) Rich Test

^ Decel Fuel cutoff mode active
^ Closed Loop
^ time elapsed is at least 2 seconds
^ HO2S (Bank 2 Sensor 2) DTCs not active since code clear
^ HO2S voltage is greater than (486 mV) 0.468V.

Action Taken When the DTC Sets
A current DTC P0158 will cause the system to operate in Open Loop. With a current DTC P0158 set, the Malfunction Indicator Lamp (MIL) will be illuminated after 1 test failure.

Conditions for Clearing the MIL/DTC
The VCM turns the MIL off after 3 consecutive driving trips without a fault condition present. A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 40°F from the start-up coolant temperature and the engine coolant temperature exceeds 160°F during that same ignition cycle) or the scan tool clearing feature has been used.

Diagnostic Aids
Check the following items

^ Fuel pressure. System will go rich if pressure is too high. The VCM can compensate for some increase. However, if it gets too high, DTC P0158 may be set. Refer to Fuel System Diagnosis. System Diagnosis - Fuel System
^ Rich injector. Perform the Fuel Injector Balance Test.
^ Leaking injector. Refer to Fuel System Diagnosis. System Diagnosis - Fuel System
^ Check for fuel contaminated oil.
^ EVAP canister purge. Check for fuel saturation. If full of fuel, check canister control and hoses. Refer to EVAP Control System Diagnosis. System Diagnosis - EVAP Control
^ Check for leaking fuel pressure regulator diaphragm by checking vacuum line to regulator for fuel.
^ TP sensor. An intermittent TP sensor output will cause the system to go rich due to a false indication of the throttle moving.
^ False rich indication due to silicon contamination of the HO2S. This will be indicated by DTC P0158 accompanied by lean driveability conditions and a powdery white deposit on the sensor.
^ Faulty HO2S (Bank 2 Sensor 2). If HO2S (Bank 2 Sensor 2) is internally shorted the HO2S (Bank 2 Sensor 2) voltage displayed on a scan tool will be over 1V. Try disconnecting the HO2S (Bank 2 Sensor 2); if the displayed voltage goes from over 1000 mV to around 450 mV, replace HO2S (Bank 2 Sensor 2).

NOTE: Never solder the HO2S wires.

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.

1. Determines if conditions necessary to set DTC P0158 exist.