GM Service Manual Online
For 1990-2009 cars only

Circuit Description

Heating elements inside the heated oxygen sensor (HO2S) minimize the time required for the sensors to reach operating temperature and provide an accurate voltage signal. A low side driver within the engine control module (ECM) is pulse width controlled to provide current to the heater elements. The ECM will not allow continuous HO2S heating until calibrated limits of time, temperature, and intake airflow have been reached. The ECM will observe the activity of HO2S to determine if it has become active within a certain time period, after start-up. If the sensor has not become active within an expected time period, after start-up, the ECM will force a rich and lean state and wait for a response from the sensor. If the sensor still does not respond, a failure is reported and DTC P0135 or DTC P0155 will set. If the sensor is active within an expected time period, after engine start-up, the ECM will wait a calibrated amount of time and then begin calculating the temperature of the sensor. If the temperature of the sensor moves outside a calibrated range, a failure counter is incremented. If the number of failures exceed a calibrated amount, DTC P0135 will set for bank 1 sensor 1 or DTC P0155 will set for bank 2 sensor 1. A small reference voltage of approximately 4.5 volts is present at the heater low control circuit.

Conditions for Running the DTC

    • DTCs P0030, P0031, P0032, P0036, P0037, P0038, P0050, P0051, P0052, P0056, P0057, P0058, P0101, P0102, P0103, P0106, P0107, P0108, P0131, P0132, P0133, P0135, P0137, P0138, P0139, P0140, P0141, P0151, P0152, P0153, P0155, P0157, P0158, P0159, P0160, P0161, P1137, P1138, P1157, P1158, P2231, P2234, P2237, P2240, P2243, P2247, P2251, P2254, P2626, P2629, are not set.
    • The engine is running.
    • The ignition 1 signal parameter is more than 10 volts.
    • The HO2S Heater Bn 1 Sen. 1 or HO2S Heater Bn 2 Sen. 1 is more than 14.8 percent.

Conditions for Setting the DTC

The HO2S has not shown the proper activity after a forced lean or rich state has been commanded for more than 25 seconds duration.

OR

The HO2S shows the proper activity, but the calculated temperature of the HO2S falls below 600°C (1,112°F) or exceeds 900°C (1,652°F), during 28 of 32 samples.

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: Engine Controls Connector End Views or Engine Control Module Connector End Views

1

Did you perform the Diagnostic System Check-Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

If DTCs P2251 or P2254 are also set, diagnose those DTCs first.

Is DTC P2251, or P2254 also set?

--

Go to DTC P2251 or P2254

Go to Step 3

3

  1. Start the engine.
  2. Allow the engine to reach operating temperature. Refer to Scan Tool Data List .
  3. Cycle the throttle from idle to wide open throttle (WOT) 3 times within 5 seconds.
  4. Observe the affected HO2S Bank 1 Sensor 1 or HO2S Bank 2 Sensor 1 parameter, with a scan tool.

Does the lambda value reach the specified value when the engine decelerates?

1.989

Go to Step 4

Go to Step 5

4

  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 5

Go to Intermittent Conditions

5

  1. Turn OFF the ignition.
  2. Inspect the exhaust system for any leaks upstream from the affected heated oxygen sensor (HO2S).
  3. Inspect for any exhaust leaks between the HO2S 1 and the HO2S 2.
  4. Repair the exhaust leak, as necessary. Refer to Exhaust Leakage in Engine Exhaust.

Did you find and correct the condition?

--

Go to Step 11

Go to Step 6

6

  1. Disconnect the connector for the HO2S 1 that applies to this DTC.
  2. Visually and physically inspect for the following items:
  3. • The HO2S 1 is securely installed
    • Terminal corrosion or water intrusion
    • Terminal tension at the HO2S 1 connectors
    • Damaged wiring
  4. Repair as necessary. Refer to Heated Oxygen Sensor Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 11

Go to Step 7

7

  1. Disconnect the engine control module (ECM).
  2. Measure the resistance of the following circuits with a DMM:
  3. • The HO2S reference voltage circuit
    • The HO2S low reference circuit
    • The HO2S heater low control circuit
    • The ignition 1 voltage circuit

Refer to Circuit Testing in Wiring Systems.

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

5 ohms

Go to Step 9

Go to Step 8

8

Test for an intermittent and poor connections at the affected HO2S 1. Refer to Testing for Intermittent Conditions and Poor Connections , Connector Repairs , and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 11

9

Repair the circuits with high resistance. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 11

--

10

Replace the affected HO2S. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 .

Did you complete the replacement?

--

Go to Step 11

--

11

  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 12

12

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 in Vehicle DTC Information

System OK