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 monitors the current flow through the heater for diagnosis. If the ECM detects that the current is above or below a specified range, DTCs P0135 sets.

DTC Descriptors

This diagnostic procedure supports the following DTC:

DTC P0135 HO2S Heater Performance Sensor 1

Conditions for Running the DTC

    • The Ignition 1 parameter is more than 10.9 volts.
    • The engine is running.
    • The affected HO2S Heater Command parameter is ON.
    • DTC P0135 runs twice per drive cycle when the above conditions are met.

Conditions for Setting the DTC

    • The ECM detects that the affected HO2S Heater Current parameter is more than 1.502 amps or less than 0.249 amps.
    • DTC P0135 sets within 5 seconds when the above condition is met.

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

Value(s)

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

2

  1. Start the engine.
  2. Command the heated oxygen sensor (HO2S) 1 heater ON with a scan tool.
  3. Wait 15 seconds to allow the HO2S heater current to stabilize.
  4. Observe the HO2S 1 heater current parameter with a scan tool.

Is the HO2S 1 heater current parameter within the specified range?

0.249-1.502 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?

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Go to Step 4

Go to Testing for Intermittent Conditions and Poor Connections

4

Inspect the EMISS fuse.

Is the EMISS fuse open?

--

Go to Step 5

Go to Step 6

5

Test the ignition 1 voltage circuit for a short to ground or for a short to the low signal circuit. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 20

Go to Step 8

6

  1. Disconnect the HO2S 1.
  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?

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Go to Step 7

Go to Step 17

7

  1. Connect a test lamp between the ignition 1 voltage circuit of the HO2S 1 harness connector on the engine harness side and the HO2S 1 heater low control circuit of the HO2S 1 harness connector on the engine harness side.
  2. Command the HO2S 1 heater ON and OFF with a scan tool.

Does the test lamp turn ON and OFF with each command?

--

Go to Step 9

Go to Step 10

8

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

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

Is any sensor shorted to ground?

--

Go to Step 18

Go to Testing for Intermittent Conditions and Poor Connections

9

Measure the resistance of the following circuits with a DMM:

    • HO2S 1 heater low control circuit
    • Ignition 1 voltage circuit

Refer to Circuit Testing .

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

3 ohms

Go to Step 16

Go to Step 14

10

Does the test lamp remain illuminated with each command?

--

Go to Step 11

Go to Step 12

11

Test the HO2S 1 heater low control circuit for a short to ground or for a short to the low signal circuit. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 20

Go to Step 19

12

Test the HO2S 1 heater low control circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 20

Go to Step 13

13

Test the HO2S 1 heater low control circuit for an open or for a high resistance. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 20

Go to Step 15

14

Test for an intermittent and for a poor connection at the HO2S 1. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 20

Go to Step 18

15

Test for an intermittent and for a poor connection 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 20

Go to Step 19

16

Repair the circuit with high resistance. Refer to Wiring Repairs .

Did you complete the repair?

--

Go to Step 20

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17

Repair the open or high resistance in the ignition 1 voltage circuit. Refer to Wiring Repairs .

Did you complete the repair?

--

Go to Step 20

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18

Replace the HO2S 1. Refer to Heated Oxygen Sensor 1 Replacement .

Did you complete the replacement?

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Go to Step 20

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19

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

Did you complete the replacement?

--

Go to Step 20

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20

  1. Replace the EMISS 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 21

21

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

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Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK