GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The heated oxygen sensor (HO2S) must reach operating temperature to provide an accurate voltage signal. A heating element inside the HO2S minimizes the time required for the sensor to reach operating temperature. Voltage is provided to the heater by the ignition 1 voltage circuit through a fuse. With the engine running, ground is provided to the heater by the HO2S heater low control circuit, through a low side driver within the engine control module (ECM). The ECM commands the heater ON or OFF to maintain a specific HO2S operating temperature range. The ECM determines the temperature by measuring the current flow through the heater. When the heater is in the ON state, the ECM will pulse the heater OFF for a duration of 50 ms, once per second. When the heater is in the OFF state, the ECM will pulse the heater ON for a duration of 50 ms, once per second. The ECM monitors the heater current with the engine running. The ECM also calculates the heater resistance on a cold start. Both diagnostics will only run once per ignition cycle. If the ECM detects that the heater current or the heater calculated resistance is not within the expected range, the following DTCs will set:

    • DTC P0135 for HO2S bank 1 sensor 1
    • DTC P0141 for HO2S bank 1 sensor 2
    • DTC P0155 for HO2S bank 2 sensor 1
    • DTC P0161 for HO2S bank 2 sensor 2

DTC Descriptors

This diagnostic procedure supports the following DTCs:

    • DTC P0135 HO2S Heater Performance Bank 1 Sensor 1
    • DTC P0141 HO2S Heater Performance Bank 1 Sensor 2
    • DTC P0155 HO2S Heater Performance Bank 2 Sensor 1
    • DTC P0161 HO2S Heater Performance Bank 2 Sensor 2

Conditions for Running the DTC

Heater Current Test

    • DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0442, P0443, P0446, P0449, P0455, P0496, P1258, P1516, P2101, P2135, P2176 are not set.
    • The Engine Coolant Temperature (ECT) Sensor parameter is more than 50°C (122°F).
    • The Ignition 1 Signal parameter is between 10-18 volts.
    • The Mass Air Flow (MAF) Sensor parameter is between 3-40 g/s.
    • The Engine Speed parameter is between 500-3,000 RPM.
    • The Engine Run Time parameter is more than 120 seconds.
    • The above conditions are met for 2 seconds.
    • This diagnostic runs one time per ignition drive cycle when the above conditions are met.

Heater Resistance Test

    • DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0442, P0443, P0446, P0449, P0455, P0496, P1258, P1516, P2101, P2135, P2176 are not set.
    • The ignition is OFF for more than 10 hours.
    • The ECT Sensor parameter is between -30 and +45°C (-22 and +113°F) at engine start-up.
    • The ECT Sensor parameter minus the Intake Air Temperature (IAT) Sensor parameter is less than 8°C (14°F) at engine start-up.
    • The engine is started.
    • The above conditions are met for up to 100 seconds.
    • This diagnostic runs one time per valid cold start when the above conditions are met.

Conditions for Setting the DTC

Heater Current Test

    • DTCs P0135 or P0155
       - The ECM detects that the affected HO2S Heater Current parameter is more than 3.125 amps or less than 0.25 amps.
       - The above condition is met for 10 seconds.
    • DTCs P0141 or P0161
       - The ECM detects that the affected HO2S Heater Current parameter is more than 1.375 amps or less than 0.25 amps.
       - The above condition is met for 10 seconds.

Heater Resistance Test

DTCs P0135, P0141, P0155, or P0161--The powertrain control module (PCM) detects that the affected HO2S heater calculated resistance is not within an expected range at engine start-up for one 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 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 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

Is DTC P0135 or P0155 set?

--

Go to Step 4

Go to Step 3

3

  1. Start the engine.
  2. Wait one minute to allow the heated oxygen sensor (HO2S) heater current to stabilize.
  3. Observe the affected HO2S Heater Current parameter with a scan tool.

Is the HO2S Heater Current parameter within the specified range?

0.25-1.375 A

Go to Step 5

Go to Step 8

4

  1. Start the engine.
  2. Wait one minute to allow the HO2S heater current to stabilize.
  3. Observe the affected HO2S Heater Current parameter with a scan tool.

Is the HO2S Heater Current parameter within the specified range?

0.25-3.125 A

Go to Step 5

Go to Step 8

5

Observe the Freeze Frame/Failure Records for this DTC.

Did the DTC fail with an engine run time of less than 10 seconds?

--

Go to Step 6

Go to Step 7

6

  1. Operate the vehicle within the Conditions for Running the Heater Resistance Test.
  2. Start the engine.

Did the DTC fail this ignition?

--

Go to Step 8

Go to Intermittent Conditions

7

  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 Heater Current Test. 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 8

Go to Intermittent Conditions

8

  1. Turn OFF the ignition.
  2. Inspect the fuse that supplies the applicable HO2S heater.

Is the fuse open?

--

Go to Step 9

Go to Step 10

9

Test the ignition 1 voltage circuit for a short to ground. Refer to the following in Wiring Systems:

    •  Circuit Testing
    •  Wiring Repairs

Did you find and correct the condition?

--

Go to Step 23

Go to Step 12

10

  1. Disconnect the affected HO2S.
  2. Turn ON the ignition, with the engine OFF.
  3. Probe the ignition 1 voltage circuit of the HO2S harness connector on the engine harness side with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors .

Does the test lamp illuminate?

--

Go to Step 11

Go to Step 20

11

  1. Turn OFF the ignition.
  2. Probe the HO2S heater low control circuit of the HO2S harness connector on the engine harness side with a test lamp connected to battery voltage.
  3. Observe the test lamp with the ignition still OFF.

Does the test lamp illuminate?

--

Go to Step 15

Go to Step 13

12

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

Is the sensor shorted to ground?

--

Go to Step 21

Go to Intermittent Conditions

13

Start the engine with the test lamp still connected from the previous step.

Is the test lamp ON steady or blinking?

--

Go to Step 14

Go to Step 16

14

Measure the resistance of the following circuits with a DMM:

    • The HO2S heater low control circuit
    • The ignition 1 voltage circuit

Refer to Circuit Testing .

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

3ohms

Go to Step 20

Go to Step 18

15

Test the HO2S heater low control circuit for a short to ground. Refer to the following in Wiring Systems:

    •  Circuit Testing
    •  Wiring Repairs

Did you find and correct the condition?

--

Go to Step 23

Go to Step 19

16

Test the HO2S heater low control circuit for a short to voltage. Refer to the following in Wiring Systems:

    •  Circuit Testing
    •  Wiring Repairs

Did you find and correct the condition?

--

Go to Step 23

Go to Step 17

17

Test the HO2S heater low control circuit for an open or for high resistance. Refer to the following in Wiring Systems:

    •  Circuit Testing
    •  Wiring Repairs

Did you find and correct the condition?

--

Go to Step 23

Go to Step 19

18

Test for shorted terminals and for poor connections at the HO2S. Refer to the following in Wiring Systems:

    •  Connector Repairs

Did you find and correct the condition?

--

Go to Step 23

Go to Step 21

19

Test for shorted terminals and for poor connections at the engine control module (ECM). Refer to the following in Wiring Systems:

    •  Connector Repairs

Did you find and correct the condition?

--

Go to Step 23

Go to Step 22

20

Repair the open or high resistance in the circuit. Refer to Wiring Repairs and Heated Oxygen Sensor Wiring Repairs .

Did you complete the repair?

--

Go to Step 23

--

21

Replace the affected HO2S. Refer to the following procedures:

Did you complete the replacement?

--

Go to Step 23

--

22

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

Did you complete the replacement?

--

Go to Step 23

--

23

Were you sent to this diagnostic from DTC P0134 or P0154?

--

Go to DTC P0134 or P0154

Go to Step 24

24

Were you sent to this diagnostic from DTC P0140 or P0160?

--

Go to DTC P0140 or P0160

Go to Step 25

25

  1. Replace the fuse, if necessary.
  2. Clear the DTCs with a scan tool.
  3. Turn OFF the ignition for 30 seconds.
  4. Start the engine.
  5. 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 26

26

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