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 P0134: HO2S Circuit Insufficient Activity Bank 1 Sensor 1
DTC P0154: HO2S Circuit Insufficient Activity 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 | P0130, P0134 | P0132 | P0130, P0133
HO2S Bank 1 Sensor 2 Signal | P0137 | P0140 | P0138 | P0139
HO2S Bank 2 Sensor 1 Signal | P0151 | P0150, P0154 | P0152 | P0150, P0153
HO2S Bank 2 Sensor 2 Signal | P0157 | P0160 | P0158 | P0159
Low Reference | -- | P0130, P0150 | P0134, P0140, P0154, P0160 | --

### Circuit Description

The wide band heated oxygen sensor (HO2S) measures the amount of oxygen in the exhaust system and provides more information than the switching style HO2S. The wide band sensor consists of an oxygen sensing cell, an oxygen pumping cell, and a heater. The exhaust gas sample passes through a diffusion gap between the sensing cell and the pumping cell. The engine control module (ECM) supplies a voltage to the HO2S and uses this voltage as a reference to the amount of oxygen in the exhaust system. An electronic circuit within the ECM controls the pump current through the oxygen pumping cell in order to maintain a constant voltage in the oxygen sensing cell. The ECM monitors the voltage variation in the sensing cell and attempts to keep the voltage constant by increasing or decreasing the amount of current flow, or oxygen ion flow, to the pumping cell. By measuring the amount of current required to maintain the voltage in the sensing cell, the ECM can determine the concentration of oxygen in the exhaust. The HO2S voltage is displayed as a lambda value. A lambda value of 1 is equal to a stoichiometric air fuel ratio of 14.7:1. Under normal operating conditions, the lambda value will remain around 1. When the fuel system is lean, the oxygen level will be high and the lambda signal will be high or greater than 1. When the fuel system is rich, the oxygen level will be low, and the lambda signal will be low or less than 1. The ECM uses this information to maintain the correct air/fuel ratio. If the ECM detects that the HO2S signal voltage is low, this DTC sets.

### Conditions for Running the DTCs

• | DTCs P0116, P0117, P0118, P0119, P0201, P0202, P0203, P0204, P0205, P0206, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0273, P0274, P0276, and P0277 are not set.

• | The ignition voltage is greater than 11 volts.

• | The engine is operating for greater than 1 second.

• | The HO2S heater is active for greater than 25 seconds.

• | The HO2S is at operating temperature for greater than 30 seconds.

• | The primary HO2S heater duty cycle is greater than 68 percent.

• | The calculated exhaust temperature is between 600-800°C (1,112-1,472°F).

• | DTCs P0134 and P0154 run continuously once the conditions above exist for more than 5 seconds.

### Conditions for Setting the DTCs

• | A primary HO2S voltage is between 400-600 mV.

• | The calculated internal resistance of a primary HO2S is greater than 20,000 ohms when the calculated exhaust temperature is warmer than 600°C (1,112°F).

• | A corresponding primary and secondary HO2S are greater than 200 mV during a decel fuel cut-off.

• | DTC P0134 or P0154 set if any of the conditions above exist for greater than 4 seconds or for a cumulative of 50 seconds.

### Action Taken when the DTC Sets

DTCs P0134 and P0154 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P0134 and P0154 are Type B DTCs.

### Diagnostic Aids

• | The front wide band sensors do not toggle or switch like a switching HO2S. The front HO2S signals will be relatively stable for an idling engine.

• | The following table illustrates the typical voltages for the HO2S circuits:

#### HO2S Voltages

HO2S Circuit | Voltage
--- | ---

• | Ignition ON, Engine OFF

• | HO2S Disconnected

Heater Control | 4.6-5.0 V
Heater Supply Voltage | B+
Reference Voltage | 2.6-3.1 V
Low Reference | 2.2-2.7 V
Pump Current | 2.5-3.0 V
Input Pump Current | 2.5-3.0 V

### 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. Engine running at normal operating temperature, verify the scan tool Loop Status Bn 1 Sen 1 and Loop Status Bn 2 Sen 1 parameters display Closed Loop.
2. 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 are captured in the Freeze Frame/Failure Records Data List.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the applicable HO2S.
2. Ignition ON, test for 350-550 mV between the reference voltage circuit terminal 3 and the low reference circuit terminal 1.

⇒ | If less than the specified range, test the reference voltage circuit and the low reference circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the ECM.

⇒ | If greater than the specified range, test the reference voltage circuit and the low reference circuit for a short to voltage. If the circuits test normal, replace the ECM.

3. Test for 50-90 mV between the input pump current circuit terminal 4 and ground.

⇒ | If less than the specified range, test the input pump current circuit and the pump current circuit for a short to ground or an open/high resistance. If the circuits test normal, replace the ECM.

⇒ | If greater than the specified range, test the input pump current circuit and the pump current circuit for a short to voltage. If the circuits test normal, replace the ECM.

4. Verify that none of the following conditions exist:

• | The HO2S is loose

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

• | Low fuel system pressure--Refer to Fuel System Diagnosis.

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

• | Water intrusion in the HO2S harness connector

• | Fuel saturation of the evaporative emission (EVAP) canister

• | Exhaust leaks near the HO2S

• | Engine vacuum leaks

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

5. If all circuits test normal, replace the applicable 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