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For 1990-2009 cars only

Circuit Description

The wide band heated oxygen sensor (HO2S) measures the amount of oxygen in the exhaust stream more quickly and accurately than the switching style HO2S. The wide band sensor consists of an oxygen sensing cell, an oxygen pumping cell, and a heater. The exhaust gas sample passes through a diffusion gap between the sensing cell and the pumping cell. The engine control module (ECM) supplies a signal voltage to the HO2S and uses this voltage as a reference to the amount of oxygen in the exhaust system. An electronic circuit within the ECM controls the pump current through the oxygen pumping cell in order to maintain a constant signal voltage. The ECM monitors the voltage variation on the signal circuit and attempts to keep the voltage constant by increasing or decreasing the amount of current flow, or reversing the direction of the current flow to the pumping cell. By measuring the direction and amount of current required to maintain the signal voltage, the ECM can determine the concentration of oxygen in the exhaust. The signal voltage is displayed as a lambda value. A lambda value of 1 is equal to a stoichiometric air fuel ratio of 14.7:1. Under normal operating conditions, the lambda value will remain around 1. When the system is lean, the oxygen level will be high and the lambda value will be high, or more than 1. When the system is rich, the oxygen level is low and the lambda value will be low, or less than 1. If the ECM detects the possibility of current leakage between the sensor heating element or circuits and the sensor sensing cell or circuits, DTC P2231 will set for bank 1 sensor 1, or DTC P2234 will set for bank 2 sensor 1.

Conditions for Running the DTC

    • DTCs P0030, P0031, P0032, P0036, P0037, P0038, P0050, P0051, P0052, P0056, P0057, P0058, P0131, P0132, P0133, P0135, P0137, P0138, P0139, P0140, P0141, P0151, P0152, P0153, P0155, P0157, P0158, P0159, P0160, P0161, P2237, P2240, P2243, P2247, P2251, P2254, P2626, P2629 are not set.
    • The engine is running.
    • The Loop Status parameter is Closed.
    • The engine is not operating in a fuel cut-off condition.
    • The HO2S Bank 1 Sensor 1 or HO2S Bank 2 Sensor 1 heater parameter is between 15-85 percent.
    • The calculated exhaust temperature is more than 400°C (752°F).

Conditions for Setting the DTC

The ECM detects that there have been more than 80 samples out of a 100 sample block in which the lambda sensor signal has changed at the same time the sensor heater was cycled ON and OFF.

Action Taken When the DTC Sets

    • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

    • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Controls Connector End Views or Engine Control Module Connector End Views

1

Did you perform the Diagnostic System Check-Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

Important: During idle or steady throttle conditions, the lambda value will be very close to 1.000.

  1. Start the engine.
  2. Allow the engine to reach operating temperature. Refer to Scan Tool Data List .
  3. Operate the engine at 2,000 RPM for 1 minute.
  4. Observe the HO2S Bank 1 Sensor 1 or HO2S Bank 2 Sensor 1 parameter with a scan tool.

Is the lambda value varying within the specified range?

0.900-1.100

Go to Step 3

Go to Step 4

3

  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 4

Go to Intermittent Conditions

4

  1. Disconnect the connector for the heated oxygen sensor (HO2S) 1 that applies to this DTC.
  2. Visually and physically inspect for the following items:
  3. • The HO2S 1 is securely installed
    • Terminal corrosion or water intrusion
    • Terminal tension at the HO2S 1 connectors
    • Damaged wiring
  4. Repair as necessary. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 23

Go to Step 5

5

Measure the voltage from the HO2S output pump current circuit, on the engine harness side connector, to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems.

Is the voltage less than the specified value?

100 mV

Go to Step 6

Go to Step 11

6

Measure the voltage from the HO2S heater low control circuit, on the engine harness side connector, to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems.

Is the voltage less than the specified value?

100 mV

Go to Step 12

Go to Step 7

7

Is the voltage within the specified range?

100-200 mV

Go to Step 13

Go to Step 8

8

Is the voltage within the specified range?

2.4-3 V

Go to Step 14

Go to Step 9

9

Measure the voltage from the HO2S reference voltage circuit, on the engine harness side connector, to a good ground with a DMM. Refer to Circuit Testing in Wiring Systems.

Is the voltage within the specified range?

2.8-3.1 V

Go to Step 19

Go to Step 10

10

Is the voltage more than the specified value?

2.8 V

Go to Step 15

Go to Step 16

11

Is the voltage within the specified range?

1-1.5 V

Go to Step 17

Go to Step 18

12

Important: 

   • The normal open circuit voltage of the output pump current circuit is approximately 10-65 millivolts.
   • The normal open circuit voltage of the heater low control circuit is 4.3-4.6 volts.

Test the HO2S output pump current circuit for a short to the HO2S heater low control circuit. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 23

Go to Step 20

13

Important: 

   • The normal open circuit voltage of the input pump current circuit is approximately 10-65 millivolts.
   • The normal open circuit voltage of the heater low control circuit is 4.3-4.6 volts.

Test the HO2S input pump current circuit for a short to the HO2S heater low control circuit. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 23

Go to Step 20

14

Important: 

   • The normal open circuit voltage of the low reference circuit is 2.4-2.7 volts.
   • The normal open circuit voltage of the heater low control circuit is 4.3-4.6 volts.

Test the HO2S low reference circuit for a short to the HO2S heater low control circuit. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 23

Go to Step 20

15

Important: 

   • The normal open circuit voltage of the reference voltage circuit is 2.8-3.1 volts.
   • The normal open circuit voltage of the heater low control circuit is 4.3-4.6 volts.

Test the HO2S reference voltage circuit for a short to the HO2S heater low control circuit. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 23

Go to Step 20

16

Test the HO2S reference voltage circuit for an open or high resistance. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 23

Go to Step 20

17

Important: 

   • The normal open circuit voltage of the input pump current circuit is approximately 10-65 millivolts.
   • The normal open circuit voltage of the low reference circuit is 2.4-2.7 volts.

Test the HO2S input pump current circuit for a short to the HO2S low reference circuit. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 23

Go to Step 20

18

Important: 

   • The normal open circuit voltage of the output pump current circuit is approximately 10-65 millivolts.
   • The normal open circuit voltage of the low reference circuit is 2.4-2.7 volts.

Test the HO2S output pump current circuit for a short to the HO2S low reference circuit. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems.

Did find and correct the condition?

--

Go to Step 23

Go to Step 20

19

Test for poor connections and shorted terminals at the HO2S. Refer to Testing for Intermittent Conditions and Poor Connections , Connector Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 23

Go to Step 21

20

Test for poor connections and shorted terminals at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections , and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 23

Go to Step 22

21

Replace the affected HO2S. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 .

Did you complete the replacement?

--

Go to Step 23

--

22

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the replacement?

--

Go to Step 23

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23

  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 24

24

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

System OK