GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    •  Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P0133: HO2S Slow Response Sensor 1

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

HO2S Sensor 1 Signal

P0131

P0134, P0135

P0132

P0133, P2096, P2097

Low Reference

--

P0134, P0135

--

--

Circuit Description

The heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the engine is started, the control module operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. The control module supplies the HO2S with a reference, or bias voltage of about 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,000 mV. This voltage will fluctuate above and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases above bias voltage toward 1,000 mV indicates a rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.

The heating elements inside each HO2S heat the sensor to bring the sensor up to operating conditions faster. This allows the system to enter Closed Loop earlier and the control module to calculate the air-to-fuel ratio sooner.

Conditions for Running the DTCs

    • Before the ECM can report that DTC P0133, DTCs P0030, P0031, P0032, and P0135 must run and pass.
    • DTC P0036, P0037, P0038, P0130, P0137, P0138, P0140, P0141, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0443, P0458, P0459, P2096, P2097, P2177, P2178, P2179, P2088, P2089, P2090, P2232, P2235, P2270, P2271, P2272, or P2273 is not set.
    • The engine speed is 1,240-2,400 RPM.
    • The HO2S 1 is in closed loop.
    • The engine load is 18-50 percent.
    • The exhaust gas temperature is greater than 350°C (662°F).
    • The evaporative purge (EVAP) solenoid valve is commanded OFF or ON for greater than 10 seconds.
    • DTC P0133 runs continuously once the conditions above exist.

Conditions for Setting the DTCs

The ECM determines that the length of time for an HO2S 1 to switch from lean to rich and back to lean, which is called a switching cycle, has exceeded a predetermined threshold. The condition exists for 3 cycles out of a 20 cycle test sample.

Action Taken when the DTCs Set

DTC P0133 is a Type B DTC.

Conditions for Clearing the MIL/DTCs

DTC P0133 is a Type B DTC.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

  1. Verify that other DTCs are not set.
  2. If any other DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle.
  3. Engine idling, observe the scan tool HO2S 1 voltage parameter. The voltage should fluctuate above and below the range of 350-550 mV.
  4. Observe the DTC information with a scan tool. DTCs P0133 should not set.
  5. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

  1. Verify that none of the following conditions exist:
  2. • Lean or rich fuel injectors--Refer to Fuel Injector Solenoid Coil Test.
    • Water intrusion in the HO2S harness connector
    • HO2S wiring harness damage
    • Incorrect RTV sealant
    • Low or high fuel system pressure--Refer to Fuel System Diagnosis.
    • Fuel that is contaminated--Refer to Alcohol/Contaminants-in-Fuel Diagnosis.
    • Fuel saturation of the evaporative emission (EVAP) canister
    • Exhaust leaks near the HO2S
    • Engine vacuum leaks
    • Engine oil consumption
    • Engine coolant consumption
         ⇒If you find any of the above conditions, repair as necessary.
  3. If all conditions test normal, replace the B52 HO2S.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Heated Oxygen Sensor Replacement - Sensor 1
    •  Control Module References for engine control module replacement, setup, and programming