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 P2626 00: HO2S Pump Current Trim Circuit Sensor 1

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Heater Voltage Supply | P0030 00 | P0030 00 | -- | P0131 5A, P0131 12
Heater Low Control | P0031 00 | P0030 00 | P0032 00 | --
Reference Voltage (Signal) | P0131 01 | P0131 12, P2243 00 | P0131 02 | P0133 00, P0131 52, P0131 5A, P0132 52, P0132 5B
Low Reference (Ground) | P2A00 00 | P0132 02, P2243 04 | P0132 02 | --
Pump Current | P2626 00 | P2626 00 | P2626 00 | --
Trim Current | P2626 00 | P2626 00 | P2626 00 | --

### Circuit/System Description

The wide band heated oxygen sensor (HO2S) measures the amount of oxygen in the exhaust stream more quickly and accurately 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 signal 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 signal voltage. The ECM monitors the voltage variation on the signal circuit and attempts to keep the voltage constant by increasing or decreasing the amount of current flow or reversing the direction of the current flow to the pumping cell. By measuring the direction and amount of current required to maintain the signal voltage, the ECM can determine the concentration of oxygen in the exhaust. The signal voltage is displayed as a lambda value. A lambda value of 1 is equal to a stoichiometric air fuel ratio of 60:1. Under normal operating conditions, the lambda value will remain around 1. When the system is lean, the oxygen level will be high and the lambda value will be high, or more than 1. When the system is rich, the oxygen level is low and the lambda value will be low, or less than 1. The ECM uses this information to maintain the proper air fuel ratio.

### Conditions for Running the DTC

• | The ignition voltage is between 10-18 V.

• | The engine speed is greater than 80 RPM.

• | The HO2S 1 heater is at operating temperature.

• | DTC P2626 runs continuously when the above conditions are met.

### Conditions for Setting the DTC

• | The ECM detects that the HO2S 1 voltage is more than 4.81 V.

• | DTC P2626 00 sets within 4 s when the above condition is met continuously, or within 50 s when the above condition is met cumulatively.

### Action Taken When the DTC Sets

DTC P2626 00 is a Type B DTC.

### Conditions for Clearing the DTC

DTC P2626 00 is a Type B DTC.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Engine Control Module Description

#### 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. Clear the DTCs with a scan tool.
2. Operate the vehicle within the conditions for running and setting the DTC. The DTC should not set.
3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

Note: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

1. Ignition OFF, disconnect the harness connector at the B52A Heated Oxygen Sensor (HO2S).
2. Ignition ON, test for 2.9 V between the B52A Heated Oxygen Sensor (HO2S) reference voltage circuit terminal 6 and ground.

⇒ | If less than the specified range, test the reference voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

⇒ | If greater than the specified range, test the reference voltage circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

3. Test for 2.5 V between the B52A Heated Oxygen Sensor (HO2S) low reference circuit terminal 2 and ground.

⇒ | If less than the specified range, test the low reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

⇒ | If greater than the specified range, test the low reference circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

4. Test for 2.8 V between the B52A Heated Oxygen Sensor (HO2S) control circuit terminal 1 and ground.

⇒ | If less than the specified range, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

⇒ | If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

5. Test for 2.8 V between the B52A Heated Oxygen Sensor (HO2S) control circuit terminal 5 and ground.

⇒ | If less than the specified range, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

⇒ | If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

6. Ignition OFF, disconnect the X1 harness connector at the K20 Engine Control Module (ECM).
7. Test for infinite resistance between each B52A Heated Oxygen Sensor (HO2S) circuit terminals.

⇒ | If less than the specified value, repair as necessary.

8. If all circuits test normal, replace the B52A Heated Oxygen Sensor (HO2S) and verify the DTC does not reset

⇒ | If the DTC resets, replace the K20 Engine Control Module (ECM).

### 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