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

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
HO2S Sensor 1 Signal | P0131 | P0131 | P0132 | P0133
HO2S Sensor 2 Signal | P0137 | P0137 | P0138 | P0140
Low Reference | -- | P0131, P0137 | P0132, P0138 | --

### Typical Scan Tool Data

#### HO2S 1 and 2

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: Engine operating in Closed Loop Parameter Normal Range: Fluctuates above and below 350-500 mV
HO2S 1 and 2 Signal | 0 mV | 400-415 mV | 1000 mV
Low Reference | -- | 400-415 mV | 1000 mV

### Circuit/System 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

• | DTC P0030 is not set.

• | The fuel system is in closed loop.

• | The engine control module (ECM) command of the evaporative emission (EVAP) canister purge solenoid is less than 100 percent.

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

• | The vehicle speed is between 65-75 km/h (40-46 mph).

• | The engine speed is between 2,144-2,464 RPM.

• | The air flow into the engine is between 23-43 kg/h.

• | The engine is running for more than 320 seconds.

• | The DTC runs continuously once the above conditions are met.

### Conditions for Setting the DTC

The ECM detects that the average rich to lean response is more than 1.4 seconds or the lean to rich response is more than 0.7 seconds.

OR

The ECM detects a difference between the rich to lean time is more than 1 second, or the ECM detects a difference between the lean to rich time is less than 1 second.

### 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

#### 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. Engine running, observe the DTC Information with a scan tool. Verify no DTCs are set.

⇒ | If any DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle to diagnose the applicable DTC.

2. Engine running, observe the scan tool HO2S voltage parameter. The voltage should fluctuate above and below the range of 350-550 mV.
3. 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 the following conditions do not exist:

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

• | The HO2S is not securely installed.

• | Corrosion on the HO2S terminals

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

• | HO2S wiring damage

• | Fuel that is contaminated--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

• | 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, test or replace the HO2S sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Heated Oxygen Sensor 1 Replacement

• | Control Module References for ECM replacement, setup, and programming