P0152

Diagnostic Chart:

Wiring Diagram:

Circuit Description
The VCM supplies a voltage of about 0.45 volt (450 mV) between the HO2S High and HO2S Low circuits. (If measured with a megohm digital voltmeter, this may read as low as 0.32 volt.) The Heated Oxygen Sensor (HO2S Bank 2 Sensor 1) varies the voltage within the range of about 1.0 volt (1000 mV) if the exhaust is rich, down to about 0.10 volt (100 mV) if the exhaust is lean.

The Sensor is like an open circuit and produces no voltage when it is below 360°C (600°F). The Diagnostic Trouble Code (DTC) P0151, P0152 or an open sensor circuit or the cold sensor causes the Open Loop operation. The DTC P0152 determines if the HO2S sensor or the circuit is shorted to high by checking for a rich condition during a steady throttle. The DTC P0152 is a type A DTC.

Conditions for Setting the DTC
The following conditions will set the 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 intrusive test in progress.
^ No device controls active.
^ The system voltage measures at least 9.0 volts.

Test Enable Rich Test

^ A Closed Loop.
^ Air to fuel ratio is at least 14.5 but less than 14.8.
^ The TP is greater than 0% but less than 50%.
^ The above must meet for 5 seconds.
^ Related HO2 sensor DTCs not active since code clear.

Test Enable DFCO Rich Test

^ Decel Fuel cutoff mode is active.
^ A Closed Loop.
^ The time elapsed is at least 2 seconds.
^ Related HO2 sensor DTCs not active since code clear.

Action Taken When The DTC Sets
A current DTC causes the system to operate in an Open Loop. With the DTC set, the Malfunction Indicator Lamp (MIL) turns on at the first 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. Component Tests and General Diagnostics
^ 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 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).
^ Never solder the HO2S wires.

Test Description
The numbers below refer to the step numbers in the diagnostic table.

2. This step determines if the conditions necessary for setting the DTC P0152 exist.