P0158
Diagnostic Chart:
Electrical:
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 1.0V (1000 mV) if the exhaust is rich, to about 0.10V (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.
CONDITIONS FOR SETTING THE DTC
The following conditions will set this DTC:
^ No TP sensor DTCs
^ No EVAP DTCs
^ No IAT sensor DTCs
^ No MAP sensor DTCs
^ No ECT sensor DTCs
^ No MAF sensor DTCs
^ No Misfire DTC
^ No intrusive test in progress
^ No device controls active
^ System voltage is at least 9 volts
Test Enable (Rich Test)
^ Closed Loop
^ Air to fuel ratio is at least 14.5 but less than 14.8
^ TP is greater than 5% but less than 99%
^ Above conditions met for 5 seconds
^ The HO2S voltage is greater than 0.993 volt (993 mV)
Test Enable (DFCO Rich Test)
^ Decel Fuel cutoff mode active
^ Closed Loop
^ Time elapsed is at least 2 seconds
^ The HO2S voltage is greater than 0.468 volt (468 mV)
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 MIL (Malfunction Indicator Lamp) will be illuminated after 1 test failure.
CONDITIONS FOR CLEARING THE MIL/DTC
^ The VCM turns the MIL OFF after 3 consecutive drive trips when the test has Run and Passed and not Failed.
^ A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 22°C (40°F) from the start-up coolant temperature and the engine coolant temperature exceeds 70°C (160°F) during the same ignition cycle).
^ Use the scan tool Clear Information function.
^ Disconnect the VCM battery feed for 30 seconds.
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. Fuel Injector Balance Test
^ 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 1 V. 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).
^ Never solder the HO2S wires.
TEST DESCRIPTION
Number(s) below refer to the step number(s) on the Diagnostic Table.
2. Determines if conditions necessary to set this DTC exist.