P2234
DTC P2231 or P2234
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provide an overview of each diagnostic category.
DTC Descriptors
DTC P2231
- HO2S Signal Circuit Shorted to Heater Circuit Bank 1 Sensor 1
DTC P2234
- HO2S Signal Circuit Shorted to Heater 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 P2231 or P2234 failed, DTC P0030, P0031, P0032, P0050, P0051, P0052, P0053, P0059, P0130, P0135, P0150, and P0155 must run and pass.
* The calculated exhaust temperature is less than 800°C (1,472°F).
* The engine load is greater than 40 percent.
* The HO2S heater is at operating temperature for greater than 10 seconds.
* The engine is not operating in decel fuel cut-off (DFCO).
* The ignition voltage is between 11-18.0 volts.
* The engine has cycled ON and OFF between 6-16 times dependent on coolant temperature.
* The total engine OFF time is greater than 240 seconds.
* The engine speed is greater than 25 RPM.
* The HO2S heater duty cycle is between 20-80 percent.
* The desired lambda and the actual lambda are within 0.05.
* DTC P2231 and P2234 run continuously once the above conditions are met for greater than 15 seconds.
Conditions for Setting the DTC
* The ECM detects the internal HO2S voltage signal change is greater than 19 mA as the heater control switches ON and OFF.
* The above condition occurs 18 times within the sample period, then 4 seconds.
Action Taken when the DTC Sets
DTCs P2231 and P2234 are Type B DTCs.
Conditions for Clearing the MIL/DTC
DTCs P2231 and P2234 are Type B DTCs.
Diagnostic Aids
* The front wide band sensor does not toggle or switch like a switching HO2S. The front HO2S signal will be relatively stable for an idling engine.
* The following table illustrates the typical voltages for the HO2S circuits:
Reference Information
Schematic Reference
Engine Controls Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition ON, observe the scan tool DTC information. Verify that DTCs P0131, P0132, P0151, or P0152 are not set.
• If any of the listed DTCs are set refer to DTC P0131 or P0151 (P0131) or DTC P0132 or P0152 (P0132)
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, open the hood to disable the Auto-Stop function.
2. Ignition ON, verify the scan tool hood position parameter displays Open.
• If the hood position does not display Open, refer to DTC P254F (P254F).
3. Ignition OFF, disconnect the harness connector of the appropriate HO2S.
4. Ignition ON, test for 2.5-3.5 V between the reference voltage circuit terminal 6 and ground.
• If greater than the specified range, test the reference voltage circuit for a short to the heater control circuit. If the circuit tests normal, replace the ECM.
5. Test for 2-3 V between the low reference circuit terminal 2 and ground.
• If greater than the specified range, test the low reference circuit for a short to the heater control circuit. If the circuit tests normal, replace the ECM.
6. Test for 2-3 V between the input pump circuit terminal 1 and ground.
• If greater than the specified range, test the input pump circuit and pump current circuit for a short to the heater control circuit. If the circuit tests normal, replace the ECM.
7. If all circuits/connections test normal, replace the appropriate HO2S.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 (Service and Repair)
* Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 (Service and Repair)
* Control Module References (Programming and Relearning) for engine control module replacement, setup, and programming