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: O2 Sensor Pump Current Trim Circuit Malfunction (Bank 1 Sensor 1)
DTC P2627: O2 Sensor Pump Current Trim Circuit Low Voltage (Bank 1 Sensor 1)
DTC P2628: O2 Sensor Pump Current Trim Circuit High Voltage (Bank 1 Sensor 1)
DTC P2629: O2 Sensor Pump Current Trim Circuit Malfunction (Bank 2 Sensor 1)
DTC P2630: O2 Sensor Pump Current Trim Circuit Low Voltage (Bank 2 Sensor 1)
DTC P2631: O2 Sensor Pump Current Trim Circuit High Voltage (Bank 2 Sensor 1)

### Typical Scan Tool Data

#### HO2S 1 or 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.
Sensor Signal | 0-60 mV | 400-415 mV | 5000 mV
Low Reference | -- | 400-415 mV | 5000 mV

### 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 circuit 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 more 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 DTCs

#### DTC P2237, P2238, P2239, P2240, P2241, or P2242

• | The ignition voltage is between 10-16 volts.

• | The engine is operating in closed loop.

• | The HO2S heater is at operating temperature.

• | The ECM is commanding the lambda more than 1.03 or less than 0.97.

• | The ECM is commanding decel fuel cut-off for more than 3 seconds.

• | The ECM is commanding the lambda rich and then lean periodically with a change of more than 2 percent.

### Conditions for Setting the DTCs

#### P2627 and P2630

The ECM detects that the HO2S Pumping Current Trim Circuit voltage is low.

#### P2628 and P2631

The ECM detects that the HO2S Pumping Current Trim Circuit voltage is high.

#### P2626 and P2629

The ECM detects that the H02S Pumping Current Trim Circuit voltage is not within a predetermined range.

### Action Taken when the DTC Sets

DTC P2126, P2627, P2628, P2629, P2630 and P2613 are type B DTCs.

### Conditions for Clearing the MIL/DTC

DTC P2126, P2627, P2628, P2629, P2630 and P2613 are type B DTCs.

### 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

### Circuit/System Verification

• | Allow the engine to reach operating temperature. Engine running, Using a scan tool observe the affected HO2S parameter.

- | The HO2S 1 value should vary from below 200 mV to above 800 mV and respond to fuelling changes.

- | The HO2S 2 value should change more than 200 mV when the throttle is quickly cycled 3 times from Closed to wide open and back to Closed after running the engine at 1,500 RPM for 30 seconds.

• | If any HO2S heater DTCs are set, diagnose those DTCs first.

• | The affected HO2S may be damaged due to contamination. Prior to replacing the affected HO2S, inspect for the following sources of contamination:

Notice: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in the Preface section.

- | A silicon contaminated HO2S.

- | Engine oil consumption - Refer to Oil Consumption Diagnosis.

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

### Circuit/System Testing

1. Disconnect the affected HO2S.
2. Ignition ON install a 3-A fusible link wire between the low reference voltage and the a low reference circuit.

⇒ | Connect a DMM between the input pump current circuit and a known ground. If the voltage is not 1 volt test the for a short to ground, short to voltage or an open/high resistance. If circuit test normal replace the ECM.

3. If all circuit test normal then replace the affected H02S sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification.

• | Heated Oxygen Sensor Replacement - Bank 1 Sensor 1.

• | Heated Oxygen Sensor Replacement - Bank 2 Sensor 2.

• | Engine Control Module Replacement for engine control module replacement, setup and programming.