For 1990-2009 cars

### Circuit Description

The heated oxygen sensor (HO2S) produces a voltage that varies between 100-900 mV under normal operating conditions. The engine control module (ECM) produces a bias voltage on the HO2S signal circuit of 420-480 mV. The engine control module (ECM) supplies the sensor the reference ground circuit. The ECM monitors the signal voltage to determine if the exhaust is lean or rich. The oxygen sensor voltage is high when the exhaust is rich, and low when the exhaust is lean. The ECM constantly monitors the HO2S signal during the Closed Loop operation. If the ECM detects that the decel fuel cut-off rich-to-lean transition time is too long, DTC P0139 or P013A will be set for bank 1 sensor 2, or DTC P0159 or P013C will be set for bank 2 sensor 2. If the ECM detects that the decel fuel cut-off rich-to-lean transition is not timely, DTC P013E will be set for bank 1 sensor 2, or DTC P014A will be set for bank 2 sensor 2.

### DTC Descriptors

This diagnostic procedure supports the following DTC:

• | DTC P0139 or P013A HO2S Slow Response Bank 1 Sensor 2

• | DTC P0159 or P013C HO2S Slow Response Bank 2 Sensor 2

• | DTC P013E HO2S Delayed Response Bank 1 Sensor 2

• | DTC P014A HO2S Delayed Response Bank 2 Sensor 2

### Conditions for Running the DTC

#### P0139, P0159

• | DTC P0021, P0024, P0030, P0031, P0032, P0036, P0037, P0038, P0050, P0051, P0052, P0056, P0057, P0058, P0101, P0102, P0103, P0106, P0107, P0108, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0131, P0132, P0135, P0137, P0138, P0139, P0140, P0141, P0151, P0152, P0155, P0157, P0158, P0159, P0160, P0161, P0201-P0208, P0221, P0222, P0223, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0273, P0274, P0276, P0277, P0279, P0280, P0282, P0283, P0300, P0301-P0308, P0335, P0336, P0340, P0341, P0345, P0346, P0351-P0358, P0365, P0366, P0390, P0391, P0442, P0443, P0446, P0449, P0453, P0454, P0455, P0458, P0459 and P0496 are not set.

• | The decel fuel cut-off system is activate.

• | The rear HO2S voltage is more than 0.59 V during the Decel Fuel Cut-Off.

• | During the Decel Fuel Cut-Off (DFCO), the accumulated air mass is more than 15 grams during a transition from high voltage to low voltage.

• | Ignition 1 voltage is greater than 10.5 volts.

• | The rear HO2S is ready or under any given function, the rear HO2S Decel Fuel Cut-Off (DFCO) Test fails.

• | The rear HO2S is near mildew condition.

• | The rear HO2S heater is stable.

• | The front HO2S is ready.

• | The value of the front HO2S measured is more than 10.

• | DTC P0139 or P0159 runs continuously once the above conditions are met for more than 4 seconds.

#### P013A, P013C

• | The decel fuel cut-off system is activate.

• | The front and the rear HO2S are ready.

• | The power voltage is greater than 10.4 V.

• | The rear HO2S internal resistance is not more than the specified resistance.

• | The exhaust temperature of rear HO2S is more than or equal to 400°C (752°F).

• | The rear HO2S voltage is the value when the exhaust is rich.

• | DTC P013A or P013C runs continuously once the above conditions are met for more than 4 seconds.

#### P013E, P014A

• | The decel fuel cut-off system is activated.

• | The rear HO2S voltage is between 0.14-0.59 volts after decel fuel cut-off.

• | The front and the rear HO2S are ready.

• | The front HO2S voltage is less than 0.14 volts.

• | The power voltage is greater than 10.4 V.

• | The rear HO2S internal resistance is not more than the specified resistance.

• | The exhaust temperature of the rear HO2S is more than or equal to 400°C (752°F).

• | The rear HO2S voltage is the value when the exhaust is rich or the accumulated oxygen storage capacity is more than 15 grams.

• | DTC P013E or P014A runs continuously once the above conditions are met for more than 4 seconds.

### Conditions for Setting the DTC

#### P0139, P0159

The ECM detects that the rear HO2S voltage signal is 140 mV for 2 seconds During Decel Fuel Cut-Off.

#### P013A, P013C

The ECM detects that the rear HO2S Slow Response time is more than 0.8 second and voltage is between 0.2-0.4 volts.

#### P013E, P014A

The ECM detects that the rear HO2S Delayed Response time is greater than 6 seconds.

### 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 but 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 MIL after 4 consecutive ignition cycles that the diagnostic runs and does not fail (MIL).

• | A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

• | A history DTC clears after 40 consecutive warmup cycles, if no failures are reported by this or any other emission related diagnostic.

• | Turn the MIL OFF with a scan tool and clear the DTC.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Allow the engine to reach normal operating temperature. Refer to Scan Tool Data List .
2. Quickly cycle the throttle from closed throttle to wide open throttle (WOT) 3 times within 5 seconds, while observing the HO2S Bank 1 Sensor 2 or HO2S Bank 2 voltage parameter with a scan tool.

Does the voltage react instantly when performing the above action?

--

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 observed from the Freeze Frame/Failure Records.

Does the DTC fail this ignition?

--

Go to Step 4

Go to Intermittent Conditions

4 |

1. Turn OFF the ignition.
2. Disconnect the affected heated oxygen sensor (HO2S) 2.
3. Connect a 3-amp fused jumper wire between the HO2S high signal circuit, on the engine harness side connector, and a good ground.
4. Turn the ignition switch ON, with the engine OFF.
5. Observe the affected HO2S 2 parameter on a scan tool.

Is the voltage less than the specified value?

25 mV

Go to Step 5

Go to Step 7

5 |

1. Remove the jumper wire from the previous step.
2. Connect a 3-amp fused jumper wire between the HO2S high signal circuit and the HO2S low signal circuit, on the engine harness side connector.
3. Observe the affected HO2S 2 parameter on a scan tool.

Is the voltage less than the specified value?

25 mV

Go to Step 6

Go to Step 8

6 |

1. Remove the jumper wire from the previous step.
2. Measure the resistance of the following circuits with a DMM:

• | The HO2S heater low control circuit

• | Ignition 1 voltage circuit, refer to Circuit Testing

Is the resistance of any circuit more than the specified value?

5 Ω

Go to Step 12

Go to Step 9

7 | Test the HO2S high signal circuit for an open or high resistance. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 11
8 | Test the HO2S low signal circuit for an open or high resistance. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 11
9 | The HO2S is detecting a rich or lean exhaust condition or may be contaminated. Check for one of the following conditions:

• | HO2S connector water intrusion

• | Silicon-contaminated H02S

• | Fuel-contaminated engine oil

• | Incorrect fuel pressure -- Refer to Fuel System Diagnosis .

• | Rich fuel injectors--Refer to Fuel Injector Balance Test with Tech 2

• | Lean fuel injectors--Refer to Fuel System Diagnosis .

• | An exhaust leak between the HO2S and the engine--Refer to Exhaust Leakage .

• | Vacuum leak

• | Fuel contamination - Water, even in small amounts is delivered to the fuel injectors. The water can cause a lean exhaust to be indicated. Excessive alcohol in the fuel can also cause this condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis for the proper procedure for inspecting for contaminants.

• | An inaccurate mass air flow (MAF) sensor

Repair any of the above or similar engine conditions as necessary.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 10

10 | Test for intermittent and poor connections at the HO2S. Refer to Testing for Intermittent Conditions and Poor Connections , Connector Repairs , and Heated Oxygen Sensor Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 13
11 | Test for an intermittent and poor connections at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 14
12 | Repair the circuits with high resistance. Refer to Wiring Repairs and Heated Oxygen Sensor Wiring Repairs . Did you complete the replacement? | -- | Go to Step 15 | --
13 | Replace the affected HO2S. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 . | -- | Go to Step 15 | --
14 | Replace the ECM. Refer to Control Module References for replacement, setup and programming. Did you complete the replacement? | -- | Go to Step 15 | --
15 |

1. Clear the DTC with the 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 he vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Does the DTC fail this ignition?

--

Go to Step 2

Go to Step 16

16 | 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 | System OK