P0144
Diagnostic Chart:
Diagnostic Chart:
Wiring Diagram:
CIRCUIT DESCRIPTION
IMPORTANT: If measured with a megohm digital voltmeter, this may read as low as 0.32 volt.
The VCM supplies a voltage of approximately 0.45 volt (450 mV) between the HO2S High and the HO2S Low circuits.
When the HO2S temperature measures below 360°C (600°F) the sensor will not produce any voltage. The sensor will behave like an open circuit. This will result in an open loop operation.
The HO2S heater provides for a faster sensor warm-up which allows the sensor to become active in a shorter period of time. The sensor will also remain active during a long extended idle. The DTC P0144 determines if the HO2S or circuit is shorted low by checking for a lean condition during a steady throttle and power enrichment (PE).
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 Lean Test
^ Closed Loop low MAP not active
^ Closed Loop
^ No fuel injectors turned off
^ Air to fuel ratio is at least 14.5 but less than 14.8
^ The TP is greater than 5% but less than 99%
^ The above met for 5 seconds
^ Related HO2S DTCs not active since code clear
Test Enable PE Lean Test
^ A Closed Loop
^ The Power Enrichment mode active
^ The high speed fuel cutoff not active
^ Related HO2S DTCs not active since code clear
^ Time elapse since test enable is at least 1 second
ACTION TAKEN WHEN THE DTC SET
A current DTC P0144 causes the system to operate in an Open Loop. With a current DTC P0144 set, the MIL (Malfunction Indicator Lamp) illuminates after 2 test failures.
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
IMPORTANT: Never solder the HO2S wires. For proper wire and connector repair refer to Wiring Repairs.
Check the following items:
^ The fuel pressure: It the pressure is too high, the system will run rich. The VCM can compensate for some increase; however, if the pressure gets too high, the DTC may set. Refer to Fuel System Diagnosis. System Diagnosis - Fuel System
^ A rich injector. Perform a poppet nozzle test. Refer to Fuel Injector Balance Test. Fuel Injector Balance Test
^ A leaking injector. Refer to Fuel System Diagnosis. System Diagnosis - Fuel System
^ Fuel contaminated oil
^ EVAP canister purge: Check for a fuel saturation. If full of fuel, check the canister control and hoses. Refer to EVAP Control System Diagnosis. System Diagnosis - EVAP Control
^ Leaking fuel pressure regulator diaphragm by checking the vacuum line to the regulator for fuel.
^ The TP sensor: An intermittent TP sensor output causes the system to run rich due to a false indication of the throttle moving.
^ False rich indication due to silicon contamination of the heated oxygen sensor. A DTC P0144 accompanied by a lean driveability conditions and a powdery white deposit on the sensor indicates a false rich indication.
^ Faulty HO2S: the HO2S is internally shorted, the HO2S voltage displayed on a scan tool will be over 1.0 volt (1000 mV). Try disconnecting the HO2S, if the displayed voltage goes from over 1000 mV to around 450 mV, replace the HO2S. Refer to HO2S Replacement.
TEST DESCRIPTION
The number below refers to the step number on the diagnostic table.
2. This test determines if the conditions exist in order to set the DTC P0152.
3. If the HO2S is internally shorted, the HO2S voltage that is displayed on a scan tool will be over 1.0 volt (1000 mV).