GM Service Manual Online
For 1990-2009 cars only

Object Number: 50796  Size: SF
Engine Controls Components
Oxygen Sensors
OBD II Symbol Description Notice
Engine Controls Connector End Views
Handling ESD Sensitive Parts Notice

Circuit Description

The Powertrain Control Module (PCM) continuously monitors the oxygen sensor 1 (O2S 1) activity for 100 seconds. During the monitor period, the PCM counts the number of times that the O2S 1 switches from rich to lean and from lean to rich, then adds the amount of time that the O2S 1 took to complete all the switches. With this information, an average time for all switches can be determined. Whenever the average time to switch is too slow, a DTC P0133 will set.

Conditions For Setting The DTC

    â€¢ DTCs P0106, P0107, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0200, P0300, P0301, P0302, P0303, P0304, P0404, P0405, P0506, P0507, P1404, P1441 not set.
    â€¢ The average O2S 1 response times are greater than 249mS for rich to lean sweeps or 249mS for lean to rich sweeps.

Or

    â€¢ Engine speed is between 1600 RPM and 2600 RPM.
    â€¢ Throttle Position (TP) angle is between 8% and 20%.
    â€¢ Ratio of response times is greater than 3.5 or less than 0.4.
    â€¢ Evaporative emissions control system is commanded open for greater than 60%.
    â€¢ Purge learned memory is greater than approximately 191.

Action Taken When the DTC Sets

    â€¢ The malfunction indicator lamp (MIL) will illuminate.
    â€¢ The PCM will record the operating conditions at the time that the diagnostic fails. The Freeze Frame and Failure Records buffers will store this information.
    â€¢ A history DTC stores.

Conditions for Clearing the MIL/DTC

    â€¢ The malfunction indicator lamp (MIL) will turn OFF after 3 consecutive ignition cycles in which the diagnostic runs without a fault.
    â€¢ A history DTC will clear after 40 consecutive warm up cycles without a fault.
    â€¢ Use a scan tool to clear the DTCs.

Diagnostic Aids

DTC P0133 or slow response is most likely caused by one of the following:

    â€¢ The fuel pressure - The system will go rich if the fuel pressure is to high. The PCM can compensate for some increase, if the fuel pressure gets too high, a DTC P0133 may set. Refer to Fuel System Diagnosis .
    â€¢ A leaking fuel injector - A leaking or faulty fuel injector can cause the system to go rich.
    â€¢ The 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 sensor is disconnected.
    â€¢ The pressure regulator - Check for a leaking fuel pressure regulator diaphragm by checking for the presence of liquid fuel in the vacuum line to the regulator.
    â€¢ The TP sensor - An intermittent TP sensor output will cause the system to go rich due to a false indication of the engine accelerating.
    â€¢ The O2S 1 contamination - Inspect the O2S 1 for silicone contamination from fuel or use of improper RTV sealant. The sensor may have a white powdery coating and result in a high but false voltage signal (rich exhaust indication). The PCM will then reduce the amount of fuel delivered to the engine causing a severe surge or driveability problem.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

  1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored in the scan tool for later reference.

  2. Replacement PCMs must be reprogrammed and the crankshaft position system variation procedure must be performed. Refer to the latest Techline information for PCM reprogramming and also refer to the Powertrain Control Module (PCM) for the Crankshaft Position System Variation Procedure.

  3. If no malfunctions have been found at this point and no additional DTCs were set, refer to Diagnostic Aids for additional checks and information.

DTC P0133-Oxygen Sensor (O2S) Circuit Slow Response (Sensor 1)

Step

Action

Value(s)

Yes

No

1

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to

Powertrain On Board Diagnostic (OBD) System Check

2

Were any component DTCs set?

--

Go to Component DTC tables

Go to Step 3

3

  1. Install a scan tool.
  2. Engine running at the normal operating temperature.
  3. Operate the vehicle within the parameters specified under Conditions For Setting The DTC .
  4. Monitor the Lean/Rich Avg. (ms), Rich/Lean Avg. (ms), and Rich/Lean to Lean/Rich Ratio Bank 1 Sensor 1 (greater than, less than).

Do the parameters show averages less than the specified values or ratios less than or greater than the specified values?

249 ms

249 ms

0.4

3.4

Go to Step 4

Go to Step 18

4

Visually/physical inspect the following items:

    â€¢ O2S 1 is securely installed.
    â€¢ Check for corrosion on the terminals.
    â€¢ Check for terminal tension (At O2S 1 and at the PCM).
    â€¢ Check the O2S 1 ground circuit for a good connection.
    â€¢ Check for damaged wiring.

Was a problem found in any of the above areas?

--

Go to Step 9

Go to Step 5

5

Check the exhaust manifold for an exhaust leak near the engine and repair as necessary.

Was a repair necessary?

--

Go to Step 3

Go to Step 6

6

  1. Turn the ignition switch OFF.
  2. Disconnect the O2S 1 electrical connector.
  3. Using the scan tool, monitor the O2S 1 voltage.

Does the scan tool voltage indicate voltage within specified values?

407-509 mV

Go to Step 7

Go to Step 10

7

  1. connect a jumper wire to the O2S 1 high signal circuit (PCM side) to ground.
  2. Using the scan tool, monitor the O2S 1 voltage.

Does the scan tool voltage indicate the voltage below the specified value?

200 mV

Go to Step 8

Go to Step 11

8

Replace the Oxygen Sensor (O2S 1).

Notice: Determine and correct the cause of the contamination in order to prevent damage to the replacement sensors.

    â€¢ Fuel contamination.
    â€¢ Use of improper RTV sealant.
    â€¢ Engine oil/coolant consumption.

Is the action complete?

--

Go to Step 17

--

9

Repair the condition as necessary.

Is the action complete?

--

Go to Step 17

--

10

Repair the O2S 1 sensor signal circuit for a short to ground.

Is the action complete?

--

Go to Step 17

--

11

  1. Remove the jumper wire.
  2. Using a DVM measure the voltage between the O2S 1 high signal circuit and ground.

Does the O2S 1 voltage measure above the specified value?

407 mV

Go to Step 12

Go to Step 13

12

  1. Turn the ignition switch OFF.
  2. Disconnect the PCM electrical connectors and check the O2S 1 low circuit for continuity
  3. If the O2S 1 low circuit measures over the specified value, repair the open or poor connection as necessary.

Was a repair necessary?

5ohms

Go to Step 17

Go to Step 14

13

  1. Turn the ignition switch OFF.
  2. Disconnect the PCM electrical connectors and check the O2S 1 sensor signal circuit for continuity
  3. If the O2S 1 sensor signal circuit measures over the specified value, repair the open or poor connection as necessary.

Was a repair necessary?

5ohms

Go to Step 17

Go to Step 15

14

Check the O2S 1 sensor low circuit terminal connection at the PCM and then replace the terminal if necessary.

Did the terminal require replacement?

--

Go to Step 17

Go to Step 16

15

Check the O2S 1 sensor signal circuit terminal connection at the PCM and replace the terminal if necessary.

Did the terminal require replacement?

--

Go to Step 17

Go to Step 16

16

Replace the PCM.

Is the action complete?

--

Go to Step 17

--

17

  1. Using the scan tool, clear the DTCs.
  2. Start the engine and idle at normal operating temperature.
  3. Operate the vehicle within the conditions for setting this DTC as specified in the supporting text.

Does the scan tool indicate that this diagnostic ran and passed?

--

Go to Step 18

Go to Step 2

18

Check if any additional DTCs are set.

Are any DTCs displayed that have not been diagnosed?

--

Go to applicable DTC table

System OK

Refer to Diagnostic Aids