For 1990-2009 cars

Table 1: | HO2S Voltages

### Circuit Description

The heated oxygen sensor (HO2S) heater reduces the time required for the oxygen sensor to reach operating temperature and maintains the operating temperature during extended idle periods. When the ignition is turned to the ON position, ignition voltage is supplied directly to the sensor heater. The engine control module (ECM) controls the heater operation by first modulating the control circuit to ground when the sensors are cold. This prevents the possibility of thermal shock to the sensor, from condensation build-up on the sensor, by controlling the sensors rate of heating. After a predetermined amount of time, the ECM commands the heaters ON continuously. Once the sensor reaches operating temperature, the ECM may modulate the heater control circuit to ground to maintain a desired temperature.

The ECM measures the HO2S sensing cell internal resistance. If the ECM detects that the HO2S sensing cell internal resistance is too high, this DTC sets.

### DTC Descriptors

This diagnostic procedure supports the following DTCs:

• | DTC P0135 HO2S Heater Performance Bank 1 Sensor 1

• | DTC P0155 HO2S Heater Performance Bank 2 Sensor 1

### Conditions for Running the DTC

#### Condition 1

• | Before the ECM can report DTC P0135 or P0155 failed, DTCs P0030, P0031, P0032, P0050, P0051, P0052, P0101, P0102, P0103, P0121, P0122, P0123, P0131, P0132, P0151, P0152, P0221, P0222, P0223, P0335, P0336, P0338, P167A, P167B, P2237, P2240, P2243, P2247, P2251, and P2254 must run and pass.

• | The ignition 1 voltage is between 10.5-18 volts.

• | The heated oxygen sensors heater is at maximum functional state.

• | The engine control module (ECM) detects that the exhaust time is more than 250 seconds.

• | The ECM detects the fuel cut-off time is more than 28 seconds or the HO2S heater is commanded ON the first time more than 25 seconds.

• | The heated oxygen sensors (H2OS) heater control is not turned OFF.

• | The calculated exhaust temperature is invalid.

• | DTC P0135 and P0155 run continuously once the above conditions are met for 1 minute.

#### Condition 2

• | Before the ECM can report DTC P0135 or P0155 failed, DTCs P0030, P0031, P0032, P0050, P0051, P0052, P0101, P0102, P0103, P0121, P0122, P0123, P0131, P0132, P0151, P0152, P0221, P0222, P0223, P0335, P0336, P0338, P167A, P167B, P2237, P2240, P2243, P2247, P2251, and P2254 must run and pass.

• | The ignition 1 voltage is between 10.5-18 volts.

• | The ECM internal sensing element resistance test is enabled.

• | The fuel injectors are not disabled.

• | If the engine is operating and then the ignition is turned OFF, the engine must be OFF for at least 5 minutes before the next start-up for the diagnostic to run.

• | The engine coolant temperature (ECT) is more than -30 °C (-22 °F) during the starting.

• | The HO2S is at operating temperature.

• | The ECM dose not detect that the internal sensing element resistance signal of the HO2S has much modification request.

• | The ECM detects that the HO2S heater control is not turned OFF.

• | DTC P0135 and P0155 runs continuously once the above condition is met for more than 70 seconds.

### Conditions for Setting the DTC

#### Condition 1

• | The Engine Control Module (ECM) detects that the calculated HO2S temperature is below the specified value.

• | The condition exists for more than 4 seconds.

#### Condition 2

• | The Engine Control Module (ECM) detects that the calculated HO2S temperature is above the specified value.

• | The condition exists for more than 4 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 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 4 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.

### Diagnostic Aids

• | Use the J 35616-A/BT-8637 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.

• | The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to Front of Vehicle/Engine Compartment Component Views.

• | The front wide band sensors do not toggle or switch like a switching HO2S. The front HO2S signals will be relatively stable for an idling engine.

• | For an intermittent condition, refer to Intermittent Conditions.

• | The following table illustrates the typical voltages for the HO2S circuits:

#### HO2S Voltages

HO2S Circuit | Voltage
--- | ---

• | Turn the ignition switch ON, with the engine OFF.

• | HO2S Disconnected

Heater Control | 4.6-5 V
Heater Supply Voltage | B+
Reference Voltage | 2.6-3.1 V
Low Reference | 2.2-2.7 V
Pump Current | Less than 0.5
Input Pump Current | Less than 0.5

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. This step determines if the condition exists. If there is an HO2S circuit condition, the ECM commands open loop for the applicable sensor.

2. This step tests for a bias voltage across the reference voltage circuit and the low reference circuit of the HO2S. The bias voltage that you are measuring, is the voltage difference between the reference voltage circuit and the low reference circuit. If there is a condition with the reference voltage circuit or the low reference circuit of the HO2S, the bias voltage will be more than or less than the specified value.

3. This step is testing the ignition 1 voltage circuit of the HO2S for high resistance. If the voltage at the test lamp probe is not B+, there is a high resistance condition with the circuit.

4. This step inspects the harness connector for water intrusion, corrosion, and bent or damaged pins.

5. This step inspects the harness connector for water intrusion, corrosion, and bent or damaged pins.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics Connector End View Reference: Component Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Note: DTC P0135 is for bank 1 sensor 1 and DTC P0155 is for bank 2 sensor 1.

1. Allow the engine to reach operating temperature.
2. Observe the Loop Status bank 1 sensor 1 or Loop Status bank 2 sensor 1 with a scan tool.

Does the scan tool display Closed Loop?

--

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 5 minutes.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text or as close to the Freeze Frame/Failure Records that you observed.

Does the DTC fail this ignition?

--

Go to Step 4

Go to Intermittent Conditions

4 |

1. Turn OFF the ignition.
2. Disconnect the appropriate heated oxygen sensor (HO2S).
3. Turn the ignition switch to ON position, with the engine OFF.
4. Measure the voltage between the reference voltage circuit and the low reference circuit of the HO2S with a DMM.

Is the voltage within the specified range?

350-550 mV

Go to Step 5

Go to Step 7

5 |

Note: Use the J 35616-200 Test Lamp kit for this test. If the J 35616-200 is not available, use a test lamp that measures more than 20 ohms.

1. Connect a test lamp between the ignition 1 voltage circuit of the HO2S and a good ground.
2. Measure the voltage between the probe of the test lamp and a good ground with a DMM. Refer to Measuring Voltage Drop.

Is the voltage at the specified value?

B+

Go to Step 6

Go to Step 12

6 | Test the heater control circuit of the HO2S for high resistance. Refer to Circuit Testing. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 11
7 | Measure the voltage between the reference voltage circuit of the HO2S and a good ground. Refer to Circuit Testing. Is the voltage less than the specified value? | 3.5 V | Go to Step 8 | Go to Step 9
8 | Test the low reference circuit of the HO2S for the following conditions:

• | An open

• | High resistance

• | A short to the reference voltage circuit

Refer to Circuit Testing and Wiring Repairs.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 10

9 | Test the reference voltage circuit of the HO2S for a short to voltage. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 11
10 | Test for shorted terminals and poor connections at the HO2S. 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 13
11 | Test for shorted terminals and poor connections at the engine control module (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 high resistance in the ignition 1 voltage circuit of the HO2S. Refer to Wiring Repairs. Did you complete the repair? | -- | Go to Step 15 | --
13 | Replace the HO2S. Refer to the appropriate procedure:

• | Heated Oxygen Sensor Replacement - Bank 1 Sensor 1

• | Heated Oxygen Sensor Replacement - Bank 2 Sensor 1

Did you complete the replacement?

--

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 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 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