P0152

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION

IMPORTANT: If measured with a megaohm digital voltmeter, this may read as low as 0.32 volt.

The VCM supplies a voltage of about 0.45 volt (450 mV) between the HO2S signal and the HO2S Low circuits. The Heated Oxygen Sensor (HO2S) varies the voltage from approximately 1.0 volt (1000 mV) during rich conditions to 0.10 volt (100 mV) during lean conditions.

The sensor acts like an open circuit and produces no voltage when the temperature is below 360°C (600°F). The 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 tile circuit is snorted to high by checking for a rich condition during a 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 intrusive test in progress

^ No device controls active

^ The system voltage is at least 9.0 volts

Test Enable (Rich Test)

^ 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 HO2S voltage is greater than 0.976 volt (976 mV)

^ The above conditions met for 5 seconds

Test Enable (DFCO Rich Test)

^ Decel Fuel cutoff mode is active

^ Closed Loop

^ The 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 P0151 causes the system to operate in open loop. With the DTC P0151 set, the MIL (Malfunction Indicator Lamp) turns ON at the first 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 it no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 22°C (40°F) from the startup 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

The number below refers to the step number on the diagnostic table.

2. This step determines if the conditions exist in order to set this DTC.

3. If the HO2S is internally shorted, the HO2S voltage displayed on a scan tool will be over 1.0 volt (1000 mV).