For 1990-2009 cars

### 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 Descriptor

DTC P0133: HO2S Slow Response Sensor 1

### 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.

The HO2S utilizes the following circuits:

• | A signal circuit

• | A low reference circuit

• | An ignition 1 voltage circuit

• | A heater control circuit

### Conditions for Running the DTC

• | DTCs P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0141, P0300, P0335, P0336, P0337, P0341, P0342, P0400, P0404, P0405, P0406, P0444, P0445, P0501, P1320, P1321, P1402, P1403, P1511, P1512, and P1513 are not set.

• | The engine coolant temperature is more than 70°C (158°F).

• | The evaporative emission (EVAP) purge solenoid pulse width modulation (PWM) is less than 100 percent.

• | The fuel system is in Closed Loop.

• | The engine speed is between 2,016-2,400 RPM.

• | The vehicle speed is between 60-80 km/h (28-34 mph).

• | The air flow into the engine is between 30-60 kg/h.

• | The DTC runs once per ignition cycle when the above conditions are met for 2 seconds.

### Conditions for Setting the DTC

• | The ECM detects that the HO2S rich-to-lean average response time or lean-to-rich average response time is more than 3 times the normal transition time for 10-20 minutes depending on engine load and speed.

| OR

• | The ECM detects that the HO2S signal spends more time in the rich region as compared to the lean region or the HO2S signal spends more time in the lean region as compared to the rich region for 10-20 minutes depending engine load and speed.

### Action Taken when the DTC Sets

DTC P0133 is a Type B DTC.

### Conditions for Clearing the MIL/DTC

DTC P0133 is a Type B DTC.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

• | Engine Control Module Connector End Views

• | Engine Controls 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

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Scan Tool Output Controls

### Circuit/System Verification

1. If any other HO2S DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle to diagnose the applicable DTC.
2. Operate the vehicle within the parameters specified in Conditions for Running the DTC. DTC P0133 should not set.
3. If the vehicle passes the Circuit/System Verification Test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records Data List.

### Circuit/System Testing

1. Verify that none of the following conditions exist:

• | An exhaust leak near the HO2S--Refer to Symptoms - Engine Exhaust .

• | Lean or rich fuel injectors--Refer to Fuel Injector Balance Test with Special Tool .

• | The HO2S is not securely installed.

• | Water intrusion or corrosion in the HO2S harness connector

• | Poor terminal tension at the HO2S and at the ECM

• | HO2S wiring harness damage

• | 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 EVAP canister

• | Engine vacuum leaks

• | Incorrect RTV sealant

• | Engine oil consumption--Refer to Symptoms - Engine Mechanical .

• | Engine coolant consumption--Refer to Loss of Coolant .

⇒ | If you find any of the above conditions, repair as necessary.

2. If all conditions test normal, replace the appropriate HO2S.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for engine control module replacement, setup, and programming