DTC P0140 HO2S Circuit Insufficient Activity Bank 1 Sensor 2 w/o RPO OSG
Circuit Description
The powertrain control module (PCM) supplies a voltage of about 450 mV between the heated oxygen sensor (HO2S) high and low signal circuits. The oxygen sensor varies the voltage over a range from about 1,000 mV when the exhaust is rich, down through about 10 mV when the exhaust is lean.
The PCM monitors and stores the HO2S voltage information. The PCM evaluates the HO2S voltage samples in order to determine the amount of time the HO2S voltage was out of range. The PCM compares the stored HO2S voltage samples taken within each sample period and determines if the majority of the samples are out of the operating range.
The PCM monitors the HO2S voltage and detects if the voltage goes out of the bias range. If the PCM does not detect the voltage went out of the bias range, a diagnostic trouble code (DTC) sets.
Conditions for Running the DTC
| • | No active mass air flow (MAF) DTCs |
| • | No active intake air temperature (IAT) DTCs |
| • | No active engine coolant temperature (ECT) DTCs |
| • | No active throttle position (TP) DTCs |
| • | No active injector DTCs |
| • | No active crank sensor DTCs |
| • | No active ignition control DTCs |
| • | The ignition voltage is more than 9.0 volts. |
| • | The engine run time is more than 70 seconds. |
| • | The fuel system is operating in Closed Loop. |
| • | The secondary air injection AIR), exhaust gas recirculation (EGR), and the catalyst diagnostics are not active. |
Conditions for Setting the DTC
The HO2S signal voltage is steady between 410 mV and 490 mV for 2.5 minutes.
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A last test failed, or current DTC, clears when the diagnostic runs and does not fail. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Use a scan tool in order to clear the MIL and the DTC. |
Diagnostic Aids
Important: Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.
| • | An oxygen supply inside the HO2S is necessary for proper operation. The HO2S wires provides the supply of oxygen. Inspect the HO2S wires and connections for breaks or contamination. Refer to Heated Oxygen Sensor Wiring Repairs in Wiring Systems. |
| • | For an intermittent condition, refer to Symptoms . |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The engine must be at the normal operating temperature before performing this test. For any test that requires probing the PCM or a component harness connector, use the Connector Test Adapter Kit J 35616 . Using this kit prevents damage to the harness connector terminals. Refer to Using Connector Test Adapters in Wiring Systems.
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Using the Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you can not duplicate the DTC, the information included in the Freeze Frame and/or Failure Records data can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can also be used to determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that the PCM recorded. This will isolate when the DTC failed. Refer to Symptoms .
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If the scan tool indicates the HO2S voltage goes below 200 mV, this indicates the HO2S circuits and PCM are OK.
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This step tests whether the low signal circuit from the PCM is OK. A voltage indicates the PCM and wiring are OK.
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Disconnecting the PCM allows using the DMM J 39200 in order to test continuity of the circuits. This aids in locating an open or shorted circuit. Refer to Testing for Continuity in Wiring Systems.
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Disconnecting the PCM allows using the DMM J 39200 in order to test continuity of the circuits. This aids in locating an open or shorted circuit. Refer to Testing for Continuity in Wiring Systems.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
|
Important: Inspect the HO2S for being secure before proceeding with this DTC. A sensor that is loose could cause this DTC to set.
Does the scan tool indicate the HO2S voltage varying outside the specified range? | 350-550 mV | |||
Does the scan tool indicate that this diagnostic failed this ignition? | -- | Go to Diagnostic Aids | ||
Is the HO2S voltage below the specified value? | 200 mV | |||
Does the DMM indicate near the specified value? | 5V | |||
Did you find and correct the HO2S high circuit condition? | -- | |||
Did you find and correct the HO2S low circuit condition? | -- | |||
8 |
Did you repair the condition? | -- | ||
9 | Replace the HO2S. Refer to Heated Oxygen Sensor Replacement - Bank 1 . Is the action complete? | -- | -- | |
10 |
Did you repair the condition? | -- | ||
11 |
Important:: Program the replacement PCM. Refer to Powertrain Control Module Replacement . Replace the PCM. Is the action complete? | -- | -- | |
12 |
Does the scan tool indicate that this test ran and passed? | -- | ||
13 | Select the Capture Info option and the Review Info option using the scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to the applicable DTC table | System OK |
DTC P0140 HO2S Circuit Insufficient Activity Bank 1 Sensor 2 w/ RPO OSG
Circuit Description
The heated oxygen sensor (HO2S) is a sensor designed to create a voltage relative to the oxygen content in the engine exhaust stream. The control module supplies the HO2S with signal high and low circuits. Ignition voltage and ground are supplied to the HO2S heater by independent circuits. The oxygen content of the exhaust indicates when the engine is operating lean or rich. When the HO2S detects that the engine is operating rich, the signal voltage is high and decreases the signal voltage as the engine runs leaner. This oscillation above and below the bias voltage sometimes referred to as activity or switching, can be monitored with the HO2S signal voltage.
The HO2S contains a heater that is necessary in order to quickly warm the sensor to operating temperature and to maintain the operating temperature during extended idle conditions. The HO2S needs to be at a high temperature in order to produce a voltage. Once the HO2S has reached operating temperature, the control module monitors the HO2S bias, or reference, voltage as well as the HO2S signal voltage for Closed Loop fuel control. During normal Closed Loop fuel control operation, the control module will add fuel or enrich the mixture when the HO2S detects a lean exhaust content and subtract fuel, or lean-out the mixture when the HO2S detects a rich exhaust condition.
Certain vehicle models utilize an oxygen sensor after the catalytic converter in order to monitor catalyst efficiency.
This diagnostic trouble code (DTC) determines if the HO2S is functioning properly by checking for an adequate number of HO2S voltage transitions above and below the bias range of 300-600 mV. This DTC sets when the powertrain control module (PCM) fails to detect a minimum number of voltage transitions above and below the bias range during the test period. Possible causes of this DTC are listed below:
| • | An open or a short to voltage on either the HO2S signal or HO2S low circuits |
| • | A malfunctioning HO2S |
| • | A problem in the HO2S heater or its circuit |
| • | A poor HO2S ground |
| • | An open HO2S low reference circuit |
Conditions for Running the DTC
| • | No active throttle position (TP) sensor DTCs |
| • | No active evaporative emission (EVAP) system DTCs |
| • | No active intake air temperature (IAT) sensor DTCs |
| • | No active manifold absolute pressure (MAP) sensor DTCs |
| • | No active engine coolant temperature (ECT) sensor DTCs |
| • | No active mass air flow (MAF) sensor DTCs |
| • | No active misfire DTCs |
| • | No intrusive test in progress |
| • | No device controls active |
| • | The system voltage is between 11.7-17 volts. |
| • | The engine has been running for more than 2 minutes. |
| • | The decel fuel cut-off mode (DFCO) is not active. |
| • | The ECT is more than 58°C (137°F). |
| • | The MAF is more than 13 g/s. |
| • | DTC P0135 not active |
| • | The system is in Closed Loop. |
Conditions for Setting the DTC
The heated oxygen sensor (HO2S) voltage is between 300 mV and 600 mV for more than 1 minute.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) if a failure is detected during 2 consecutive key cycles. |
| • | The control module sets the DTC and records the operating conditions at the time the diagnostic failed. The failure information is stored in the scan tool Freeze Frame/Failure Records. |
Conditions for Clearing the MIL or DTC
| • | The control module turns OFF the MIL after 3 consecutive drive trips when the test has run and passed. |
| • | A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70°C (158°F) during the same ignition cycle. |
| • | Use a scan tool in order to clear the DTCs. |
Diagnostic Aids
Important: Never solder the HO2S wires. For proper wire and connection repairs, refer to Wiring Repairs or Connector Repairs in Wiring Systems.
| • | A malfunctioning HO2S heater or heater circuit -- With the ignition ON and the engine OFF, the HO2S voltage displayed on a scan tool should gradually drop to below 0.150 volt, indicating that the heater works properly. If not, disconnect the HO2S and connect a test lamp between the terminals C and D. If the test lamp does not light, repair the open in the HO2S ground circuit or the HO2S ignition positive voltage circuit. If the test lamp lights, replace the HO2S. |
| • | The intermittent test -- Use a scan tool in order to monitor this HO2S signal voltage. Move the related connectors and the wiring harness with a warm engine running at part throttle in Closed Loop. If the failure is induced, the HO2S 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. |
An intermittent may be caused by any of the following conditions:
| • | A poor connection |
| • | Rubbed through wire insulation |
| • | A broken wire inside the insulation |
Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
If a repair is necessary, then refer to Wiring Repairs or Connector Repairs in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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This step checks for proper sensor activity. When in Closed Loop fuel control, the HO2S voltage should rapidly swing above and below the bias voltage.
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This step checks the PCM and the HIGH and LOW circuits between the PCM and the HO2S connector for proper operation.
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This step checks for proper HO2S heater circuit operation up to the HO2S connector.
Step | Action | Value(s) | Yes | No | ||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||||||||||||||
Is the HO2S voltage fixed within the voltage range specified? | 300-600 mV | |||||||||||||||||||||
3 | The condition that set this DTC is not present. This DTC may have been set by one of the following conditions:
Repair any of the above conditions as necessary. Did you find a problem? | -- | Go to Diagnostic Aids | |||||||||||||||||||
Is the voltage less than the specified value? | 20 mV | |||||||||||||||||||||
5 |
Is the resistance of both circuits less than the specified value? | 5 ohms | ||||||||||||||||||||
6 |
Did you find a problem? | -- | ||||||||||||||||||||
Is the test lamp ON? | -- | |||||||||||||||||||||
8 | Repair the HO2S heater ignition positive voltage or ground circuit. Refer to Wiring Repairs in Wiring Systems. Probable causes include the following:
Is the action complete? | -- | -- | |||||||||||||||||||
9 |
The leak may be very small and typically be within 30 cm (12 in.) of the suspect HO2S. Did you find a problem? | -- | ||||||||||||||||||||
10 | Inspect for one of the following conditions that may cause the reference voltage to be skewed:
Did you find and correct the condition? | -- | -- | |||||||||||||||||||
11 | Repair the circuit that measured high resistance. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||||||||||||||
12 |
Is the resistance less than the specified value? | 500 ohms | ||||||||||||||||||||
13 | Replace the HO2S sensor. Refer to Heated Oxygen Sensor Replacement - Bank 1 . Is the action complete? | -- | -- | |||||||||||||||||||
14 |
Important:: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | -- | |||||||||||||||||||
15 |
Does the scan tool indicate the diagnostic Passed? | -- | ||||||||||||||||||||
16 | Does the scan tool display any additional undiagnosed DTCs? | -- | Go to the applicable DTC table | System OK |
