DTC P0140 HO2S CKT Insufficient Activity Sensor 2 (1 Of 2)
DTC P0140 HO2S CKT Insufficient Activity Sensor 2 (2 Of 2)
HO2S Circuit
Circuit Description
The Vehicle Control Module (VCM) supplies a voltage of about 0.45 volt (450 mV) between the HO2S High and HO2S Low circuits. (If measured with a megaohm digital voltmeter, this may read as low as 0.32 volt.) The Heated Oxygen Sensor (HO2S Bank 1, Sensor 2) varies the voltage within the range of about 1.0 volt (1000 mV) it 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 HO2S heater provides for a faster sensor warm-up which allows the sensor to become active in a shorter period of time and remain active during a long extended idle. The DTC P0140 determines if the HO2S to the HO2S circuit has developed an open. This DTC is a type B DTC.
Conditions For Setting The DTC
The Following Conditions will set the DTC:
No Throttle Position (TP) sensor DTCs.
No Evaporation Emission (EVAP) DTCs.
No Intake Air Temperature (IAT) sensor DTCs.
No Manifold Absolute Pressure (MAP) sensor DTCs.
No Engine Coolant Temperature (ECT) sensor DTCs.
No Mass Air Flow (MAF) sensor DTCs.
No intrusive test in progress.
The system voltage measures at least 9.0 volts, The engine run time is greater than 2 minutes.
HO2S Sensor Open Test Enable
A Closed Loop.
The DTC P0141 (HO2S heater) not set.
HO2S voltage greater than 0.299 volts but less than 0.598 volts.
Engine run time is greater than 2 minutes.
HO2S (Bank 1, Sensor 2) voltage is greater than 299 mV but less than 598 mV.
Action Taken When The DTC Sets
With a current DTC set, the Malfunction Indicator Lamp (MIL) turns on after 2 test failures.
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
A poor connection, rubbed through wire insulation, or a wire broken inside the insulation may cause an intermittent.
Check for the following conditions:
A poor connection or a damaged harness: Inspect the harness connectors for the following conditions:
Backed out terminals.
Improperly formed or damaged terminals.
Poor terminal to wire connection.
Damaged harness.
A faulty HO2S (Bank 1, Sensor 2) heater or heater circuit: With the ignition switch turned ON but the engine stays off, the HO2S (Bank 1, Sensor 2) voltage displayed on a scan tool should gradually drop to below 0.300 volt, indicating that the heater works properly. If not, disconnect the HO2S (Bank 1, Sensor 2) and connect a test light between the terminals C and D. If the test light does not light, repair the open in the HO2S (Bank 1, Sensor 1) ground circuit or the HO2S (Bank 1, Sensor 2) ignition feed circuit. If the test light lights, replace the HO2S (Bank 1, Sensor 2).
The Intermittent test: With a scan tool monitor the HO2S (Bank 1, Sensor 2) signal voltage while moving the related connectors and the wiring harness with a warm engine running at part throttle in a Closed Loop. It the failure is induced, the HO2S (Bank 1, Sensor 2) signal voltage reading changes from its normal fluctuating voltage (above 600 mV and below 300 mV) to a fixed value around 450 mV. This may help to isolate the location of the malfunction.
NOTE : Never solder the HO2S wires. For proper wire and connection repairs, refer to Diagrams.
Test Description
The numbers listed below refer to the step numbers on the diagnostic table.
If the conditions for the setting DTC P0140 exist, the system will not go into a Closed Loop.
This step determines if the sensor or the wiring is the cause of the DTC P0140.
This test checks the continuity of the HO2S 2 High signal circuit.
