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 P2626: HO2S Pumping Current Trim Circuit Bank 1 Sensor 1
DTC P2629: HO2S Pumping Current Trim Circuit Bank 2 Sensor 1

### 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.

### Conditions for Running the DTC

• | Before the ECM can report DTC P2626 or P2629 failed, DTCs P0101, P0121, P0122, P0123, P0221, P0222, P0223, P0336, and P0338 must run and pass.

• | The engine is operating.

• | The ignition voltage is between 11-18 volts.

• | The fuel system is in fuel shut-off for greater than 5 seconds.

• | The calculated exhaust temperature is colder than 750°C (1,382°F).

• | The HO2S 1 is at operating temperature.

• | DTC P2626 and P2629 run continuously once the above conditions are met.

### Conditions for Setting the DTC

• | The ECM internal HO2S 1 signal voltage is greater than 4.73 volts.

• | The condition exists for greater than 4 seconds or 600 seconds if the fuel level is less than 12 percent.

### Action Taken when the DTC Sets

DTC P2626 and P2629 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTC P2626 and P2629 are Type B DTCs.

### Diagnostic Aids

• | The HO2 wide band sensor does not toggle or switch like a switching HO2S. The HO2S 1 signal will be relatively stable for an idling engine.

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

HO2S Circuit | Voltage
--- | ---

• | Ignition ON, Engine OFF

• | HO2S Disconnected

Heater Control | 4.6-5.0 V
Heater Supply Voltage | B+
High Signal | 2.6-3.1 V
Low Signal | 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. Ignition ON, observe the scan tool DTC information. Verify that DTC P0131, P0132, P0151, or P0152 is not set.

⇒ | If any of the above DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.

2. Engine idling at operating temperature. Observe the appropriate scan tool Loop Status Sen 1 parameter. The parameter should display Closed Loop.
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 are captured in the Freeze Frame/Failure Records Data List.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the appropriate HO2S 1.
2. Connect a 3A fused jumper wire between the high signal circuit terminal 3 and low signal circuit terminal 1.
3. Ignition ON, test for greater than 1 volt between the pump current circuit terminal 4 and ground.

⇒ | If less than the specified range, test the pump current circuit for an open. If the circuit tests normal, replace the ECM.

4. If all circuits test normal, replace the appropriate HO2S 1.

### 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