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 Descriptors

DTC P0133: HO2S Slow Response Bank 1 Sensor 1
DTC P0153: HO2S Slow Response Bank 2 Sensor 1

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
HO2S Bank 1 Sensor 1 Signal | P0131 | P0134, P0135 | P0132 | P0133, P2096, P2097
HO2S Bank 1 Sensor 2 Signal | P0137 | P0140 | P0138 | P0140
HO2S Bank 2 Sensor 1 Signal | P0151 | P0154, P0155 | P0152 | P0153, P2098, P2099
HO2S Bank 2 Sensor 2 Signal | P0157 | P0160 | P0158 | P0160
Low Reference | -- | P0134, P0135, P0154, P0155 | -- | --

### 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 or P0153 failed, DTCs P0030, P0031, P0032, P0050, P0051, P0052, P0135, and P0155 must run and pass.

• | DTCs P0036, P0037, P0038, P0057, P0058, P0137, P0138, P0140, P0141, P0157, P0158, P0160, P0161, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0442, P0443, P0455, P0458, P0459, P2096, P2097, P2098, P2099, P2177, P2178, P2179, P2088, P2089, P2090, P2231, P2232, P2234, P2235, P2270, P2271, P2272, and P2273 are not set.

• | The engine speed is 1,800-2,400 RPM.

• | The primary HO2S is in closed loop.

• | The engine load is 40-70 percent.

• | The exhaust gas temperature is greater than 350°C (662°F).

• | The evaporative purge (EVAP) solenoid is commanded OFF or ON for greater than 10 seconds.

• | DTC P0133 and P0153 run continuously once the conditions above exist.

### Conditions for Setting the DTCs

The ECM determines that the length of time for a primary HO2S 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

DTCs P0133 and P0153 are Type B DTCs.

### Conditions for Clearing the MIL/DTCs

DTCs P0133 and P0153 are Type B DTCs.

### 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. Verify that other DTCs are not set.

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

2. Engine idling, observe the 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. DTCs P0133 and P0153 should not set.
4. 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:

• | Lean or rich fuel injectors--Refer to Fuel Injector Balance Test with Special Tool or Fuel Injector Balance Test with Tech 2 .

• | 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.

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

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Heated Oxygen Sensor Replacement - Bank 1 Sensor 1

• | Heated Oxygen Sensor Replacement - Bank 2 Sensor 1

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