GM Service Manual Online
For 1990-2009 cars only

Circuit Description

When the vehicle is first started, the engine operates in an Open Loop operation, ignoring the oxygen sensor (O2S) signal and calculating the air/fuel ratio based on inputs from the engine coolant temperature (ECT), the throttle position (TP), and the manifold absolute pressure (MAP) sensors only. The powertrain control module (PCM) will begin by using the oxygen sensor (O2S) signal for controlling the fuel delivery, Closed Loop, when the following conditions are met:

    • The engine has run a minimum amount of time based on ECT at engine start up.
    • The oxygen sensor (O2S 1) has a varying voltage output showing that the sensor is hot enough to operate properly.
    • The ECT has increased a minimum amount based on the ECT at engine start up.

Conditions For Running The DTC

    • DTCs P0105, P0107, P0108, P0117, P0118, P0122, P0123, P0125, P0128, P0131, P0132, P0133, P0134, P0171, P0172, P0201, P0202, P0203, P0204, P0300, P0301, P0302, P0303, P0304, P0325, P0336, P0440, P0442, P0446, P0452, P0453, P0502, P0601, P0602, P1133, P1441, or P1621 are not set.
    • The engine has been running more than 100 seconds.
    • The engine speed is between 1,200-3,400 RPM.
    • The throttle position (TP) angle is between 10-40 percent.
    • The ECT is greater than 60°C (140°F).
    • The above conditions have been met for 2 seconds.

Conditions For Setting The DTC

The engine is not in Closed Loop for 5 seconds out of 12.5 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 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.

Diagnostic Aids

DTC P0130 or slow response is most likely caused by one of the following conditions:

    • The fuel pressure--The system will go rich if fuel pressure is too high. The PCM can compensate for some increase, however, if the pressure becomes too high, DTC P0172 may set. Refer to Fuel System Diagnosis .
    • A leaking injector--A leaking or malfunctioning injector can cause the system to go rich.
    • The manifold absolute pressure (MAP) sensor--An output that causes the PCM to sense a higher than normal manifold pressure (low vacuum) can cause the system to go rich. Disconnecting the MAP sensor will allow the PCM to set a fixed value for the MAP sensor. Substitute a different MAP sensor if the rich condition is gone while the MAP sensor is disconnected.
    • The fuel pressure regulator--Test for a leaking fuel pressure regulator diaphragm by inspecting for the presence of liquid fuel in the vacuum line to the fuel pressure regulator.
    • The throttle position (TP) sensor--An intermittent TP sensor output can cause the system to go rich due to a false indication of the engine accelerating.
    • O2S 1 contamination--Inspect the O2S 1 for silicone contamination from fuel or the use of improper RTV sealant. The O2S 1 sensor may have a white powdery coating and produce a high but false voltage signal, indicating a rich exhaust. The PCM will then reduce the amount of fuel delivered to the engine, causing a severe surge or driveability problem.

Test Description

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

  1. When the system is operating correctly the O2S voltage should toggle above and below the specified values.

  2. The specified value is what is measured on a correctly operating system.

  3. The specified value is what is measured on a correctly operating system.

  4. This vehicle is equipped with a PCM which utilizes an electrically erasable programmable read only memory (EEPROM). When the PCM is replaced, the new PCM must be programmed.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Important: If any other DTCs are set, except the HO2S DTCs, refer to other DTCs first before proceeding with this table.

  1. The engine is at operating temperature.
  2. Operate engine above 1,200 RPM for 2 minutes.
  3. With a scan tool, observe the O2S voltage parameter.

Does scan tool indicate O2S voltage varying outside the specified values?

400-500 mV

Go to Step 3

Go to Step 4

3

Operate vehicle within Failure Records conditions.

Does the scan tool indicate this DTC failed this ignition?

--

Go to Step 4

Go to Diagnostic Aids

4

Inspect and test for the following:

    • An exhaust leak--Refer to Exhaust Leakage in Engine Exhaust.
    • The O2S is installed correctly.
    • Damaged wiring--Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 5

5

  1. Turn OFF the ignition.
  2. Disconnect the O2S.
  3. Jumper the O2S low signal circuit to a good ground.
  4. Turn ON the ignition, with the engine OFF.
  5. Measure the voltage on the O2S high signal circuit on the PCM side, using a DMM that is connected to a good ground.

Does the voltage measure within the specified value?

351-551 mV

Go to Step 6

Go to Step 8

6

  1. Jumper the high signal circuit to the low signal circuit on the PCM side.
  2. With a scan tool, observe O2S voltage parameter.

Does the scan tool indicate O2S voltage at or near the specified value?

0 mV

Go to Step 9

Go to Step 7

7

Test the low signal circuit for an open or high resistance or for short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 11

8

Test the high signal circuit for an open or high resistance or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 11

9

Test for poor connections at the O2S. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 10

10

Important: Determine the cause of contamination before replacing the sensor.

Inspect and test for the following:

    • Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis
        Engine oil or coolant consumption--Refer to Oil Consumption Diagnosis in Engine Mechanical.
    • Use of improper RTV sealant--Refer to

Notice: Contamination of the oxygen sensor can result from the use of an inappropriate RTV sealant (not oxygen sensor safe) or excessive engine coolant or oil consumption. Remove the HO2S and visually inspect the portion of the sensor exposed to the exhaust stream in order to check for contamination. If contaminated, the portion of the sensor exposed to the exhaust stream will have a white powdery coating. Silicon contamination causes a high but false HO2S signal voltage (rich exhaust indication). The control module will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem. Eliminate the source of contamination before replacing the oxygen sensor.

in Cautions and Notices.

Replace the O2S sensor. Refer to Oxygen Sensor Replacement .

Did you complete the replacement?

--

Go to Step 13

--

11

Test for poor connections at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 12

12

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

--

Go to Step 13

--

13

  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 14

Go to Step 2

14

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK