GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2009 🢒 HHR 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC P2237, P2243, P2251, or P2626

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 P2237 : HO2S Pumping Current Control Circuit Sensor 1

DTC P2243 : HO2S Reference Voltage Circuit Sensor 1

DTC P2251 : HO2S Low Reference Circuit Sensor 1

DTC P2626 : HO2S Pumping Current Trim Circuit Sensor 1

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Heater Voltage Supply

P0030, P0130

P0030, P0053, P0130, P0135

--

Heater Low Control

P0031, P0130

P0030, P0053, P0135

P0032

Reference Voltage (Signal)

P0131

P0130, P2243

P0132

Low Reference (Ground)

P0130, P0136

P0130, P2251

P0132

Pump Current

P0130, P0131, P2237

P2237

P0132, P2237

Trim Current

P0130, P0131, P2626

P2626

P0132, P2626

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 14.7:1. 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

P2237

    • The ignition voltage is between 10.7-18.1 volts.
    • The engine is running.
    • HO2S 1 voltage is between 1.48-1.52 volts.
    • HO2S 1 heater is at operating temperature.
    • HO2S 1 closed loop is active.
    • The catalyst temperature is stable.
        AND
    • DTCs P0030, P0031, P0032, P0053, P0133, P0135 are not set.
    • The ignition voltage is between 10.7-18.1 volts.
    • The engine is running.
    • The Lambda parameter is 0.97-1.03.
    • HO2S 1 heater is at operating temperature.
    • HO2S 1 Closed Loop is active.
        AND
    • DTCs P0121, P0122, P0123, P0221, P0222, P0223, P0335, P0336, P0338 are not set.
    • The ignition voltage is between 10.7-18.1 volts.
    • The engine is running.
    • HO2S 1 heater is at operating temperature.
    • HO2S 1 Closed Loop is active.
    • Deceleration fuel cutoff (DFCO) has been active for 3 seconds.
    • DTC P2237 runs continuously when the above conditions are met for 2 seconds.

P2243

    • DTCs P0030, P0031, P0032 are not set.
    • The ignition voltage is between 10.7-18.1 volts.
    • The engine is running.
    • HO2S 1 heater is at operating temperature for at least 10 seconds.
    • DTC P2243 runs continuously when the above conditions are met for 2 seconds.

P2251

    • DTCs P0030, P0031, P0032 are not set.
    • The ignition voltage is between 10.7-18.1 volts.
    • The engine is running.
    • The HO2S 1 heater temperature has been within the normal range for more than 20 seconds.
    • HO2S 1 internal resistance is more than 950 ohms.
    • The following are true for more than 20 seconds.
       - The HO2S 1 heater is ready.
       - The engine is running.
       - The ignition voltage is more than 11 volts.
    • DTC P2251 runs continuously when the above conditions are met.

P2626

    • The ignition voltage is between 10.7-8.1 volts.
    • The engine is running.
    • Fuel cut-off is true.
    • The estimated exhaust temperature is less than 780°C (1,436°F).
    • The HO2S 1 heater is at operating temperature.
    • DTC P2626 runs continuously when the above conditions are met for 2 seconds, or when the above conditions are met for 10 minutes if the fuel level is low.

Conditions for Setting the DTC

P2237

    • The ECM detects that the pumping current circuit is open.
    • DTC P2237 sets within 1 second when the above condition is met continuously, or within 10 seconds when the above condition is met cumulatively.

P2243

    • The ECM detects that the HO2S 1 voltage is less than 0.2 volt or more than 4.7 volts.
    • DTC P2243 sets within 1 second when the above condition is met continuously, or within 10 seconds when the above condition is met cumulatively.

P2251

    • The ECM detects that the HO2S 1 reference ground circuit is open.
    • DTC P2251 sets within 1 second when the above condition is met continuously, or within 10 seconds when the above condition is met cumulatively.

P2626

    • The ECM detects that the HO2S 1 voltage is more than 4.81 volts.
    • DTC P2626 sets within 1 second when the above condition is met continuously, or within 10 seconds when the above condition is met cumulatively.

Action Taken When the DTC Sets

DTCs P2237, P2243, P2251, and P2626 are Type B DTCs.

Conditions for Clearing the DTC

DTCs P2237, P2243, P2251, and P2626 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
    •  Heated Oxygen Sensor Wiring 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

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

  1. Ignition OFF, disconnect the HO2S 1.
  2. Ignition ON, test for 2.9 volts between the HO2S 1 High Signal circuit terminal 6 and ground.
    3. ⇒If more than the specified value, test the circuit for a short to voltage. If the circuit tests normal, replace the ECM.
    ⇒If less than the specified value, test the circuit for an open/high resistance or a short to ground. If the circuit tests normal, replace the ECM.
  3. Ignition ON, test for 2.5 volts between the HO2S 1 Low Signal circuit terminal 2 and ground.
    4. ⇒If more than the specified value, test the circuit for a short to voltage. If the circuit tests normal, replace the ECM.
    ⇒If less than the specified value, test the circuit for an open/high resistance or a short to ground. If the circuit tests normal, replace the ECM.
  4. Ignition ON, test for 2.8 volts between the HO2S 1 Output Pump Current circuit terminal 1 and ground.
    5. ⇒If more than the specified value, test the circuit for a short to voltage. If the circuit tests normal, replace the ECM.
    ⇒If less than the specified value, test the circuit for an open/high resistance or a short to ground. If the circuit tests normal, replace the ECM.
  5. Ignition ON, test for 2.8 volts between the HO2S 1 Input Pump Current circuit terminal 5 and ground.
    6. ⇒If more than the specified value, test the circuit for a short to voltage. If the circuit tests normal, replace the ECM.
    ⇒If less than the specified value, test the circuit for an open/high resistance or a short to ground. If the circuit tests normal, replace the ECM.
  6. Ignition OFF, disconnect the ECM connector X1.
  7. Ignition OFF, test for infinite ohms between each HO2S 1 circuit terminal and all other HO2S 1 circuit terminals.
    8. ⇒If less than the specified value, repair as necessary.
  8. If the ECM and all circuits test normal, replace the HO2S 1.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Heated Oxygen Sensor Replacement - Sensor 1
    •  Control Module References for ECM replacement, setup, and programming