GM Service Manual Online
For 1990-2009 cars only

Circuit Description

Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started, the powertrain control module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air-to-fuel ratio. The PCM supplies the HO2S with a reference, or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage once the sensor reaches operating temperature. A high HO2S voltage output indicates a rich fuel mixture. A low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature and to provide an accurate voltage signal. The PCM controls the HO2S 2 heater low control circuit with a low side driver. The PCM commands the heater ON or OFF to maintain a specific HO2S operating temperature range. The PCM determines the temperature by measuring the current flow through the heater. When the heater is in the ON state, the PCM will pulse the heater OFF for a duration of 50 ms per second. When the heater is in the OFF state, the PCM will pulse the heater ON for a duration of 50 ms once per second. If the PCM detects that the HO2S 2 heater low control circuit current level is not within the calibrated range, DTC P0060 will set for bank 2 sensor 2.

The HO2S 2 has the following circuits:

    • The HO2S 2 high signal circuit
    • The HO2S 2 low reference circuit
    • The HO2S 2 ignition 1 voltage circuit
    • The HO2S 2 heater low control circuit

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0060 HO2S Heater Resistance Bank 2 Sensor 2

Conditions for Running the DTC

    • The ignition is OFF for more than 10 hours.
    • The ECT Sensor parameter minus the IAT Sensor parameter is less than 8°C (14°F) at engine start-up.
    • The ECT Sensor parameter is between -30 and +45°C (-22 and +133°F) at engine start-up.
    • The system voltage is between 9-18 volts.
    • This diagnostic runs once per valid cold start when the above conditions are met.

Conditions for Setting the DTC

The PCM detects that the HO2S 2 heater calculated resistance is not within an expected range at engine start-up for 1 second.

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: Powertrain Control Module Connector End Views or Engine Controls 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

2

Important: The HO2S Heater parameter may toggle to 0.00 A momentarily.

  1. Start the engine.
  2. Allow the engine to idle at operating temperature. Refer to Scan Tool Data List .
  3. Observe the affected HO2S Heater parameter with a scan tool.

Is the amperage within the specified range?

0.21-0.95 A

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 Testing for Intermittent Conditions and Poor Connections

4

Test the fuse that powers the affected heated oxygen sensor (HO2S) 2 for an open. Refer to Circuit Testing .

Is the fuse open?

--

Go to Step 8

Go to Step 5

5

Important: Use a known good ground. DO NOT use the HO2S 2 heater low control circuit or the HO2S 2 low signal circuit.

  1. Turn OFF the ignition.
  2. Disconnect the HO2S 2.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the HO2S 2 ignition 1 voltage circuit, on the engine harness side, and a good ground.
  5. Measure the voltage in parallel with the test lamp between the HO2S 2 ignition 1 voltage circuit terminal, on the engine harness side, and a good ground with a DMM.

Is the difference between the vehicle system voltage and the measured voltage greater than the specified voltage?

0.5 V

Go to Step 12

Go to Step 6

6

  1. Turn OFF the ignition.
  2. Remove the test lamp from the previous step.
  3. Connect a test lamp between the ignition 1 voltage circuit and the heater low control circuit on the engine harness side of the HO2S.
  4. Start the engine.
  5. Measure the voltage in parallel with the test lamp between the HO2S 2 heater low control circuit terminal on the engine harness side and a good ground with a DMM.

Is the voltage more than the specified value?

0.5 V

Go to Step 7

Go to Step 10

7

Test the HO2S 2 heater low control circuit for an open or high resistance condition. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 16

Go to Step 11

8

Test the HO2S 2 ignition 1 voltage circuit for a short to ground and replace the fuse. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 16

Go to Step 9

9

Important: Perform the following test on all HO2S' that are supplied voltage by the suspect circuit.

Test the ignition 1 voltage circuit on the sensor side of the HO2S connector for a short to ground. Refer to Circuit Testing .

Is any sensor shorted to ground?

--

Go to Step 14

Go to Testing for Intermittent Conditions and Poor Connections

10

Test for an intermittent and for a poor connection at the HO2S 2. 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 16

Go to Step 14

11

Test for shorted terminals and poor connections at the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 16

Go to Step 15

12

Repair the open or high resistance condition in the HO2S 2 ignition 1 voltage circuit. Refer to Wiring Repairs and Heated Oxygen Sensor Wiring Repairs .

Did you complete the repair?

--

Go to Step 16

--

13

Repair the circuit that measured high resistance. Refer to Wiring Repairs and Heated Oxygen Sensor Wiring Repairs .

Did you complete the repair?

--

Go to Step 16

--

14

Notice: Refer to Heated Oxygen Sensor Resistance Learn Reset Notice in the Preface section.

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

Did you complete the replacement?

--

Go to Step 16

--

15

Replace the PCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 16

--

16

  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 17

17

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