P2097
DTC P2097
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) provides an overview of each diagnostic category.
DTC Descriptors
DTC P2097
- Post Catalyst Fuel Trim System High Limit
Diagnostic Fault Information
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 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.
Fuel Trim Biasing is used by the ECM to keep the post catalyst HO2S voltage within a range of 580-665 mV as possible. This allows optimal catalyst efficiency under light load conditions, such as at idle or a steady cruise. The ECM constantly monitors how lean or rich the fuel trim bias is commanded.
Conditions for Running the DTC
* Before the ECM can report DTC P2097 failed, DTCs P0030, P0031, P0032, P0036, P0037, P0038, P0053, P0101, P0130, P0131, P0132, P0135, P0137, P0138, P0140, P0141, P167A, P2231, P2243, P2251, P2270, P2271, and P2626 must run and pass.
* DTCs P0133, P2237, and P2297 are not set.
* The engine is operating for greater than 2 seconds.
* The post catalyst fuel trim control is enabled.
* The front and rear HO2S are in closed loop.
* DTC P2097 runs continuously once the above conditions are met for greater than 40 seconds.
Conditions for Setting the DTC
The post catalyst fuel trim correction factor is biased rich by greater than -3 percent of the HO2S lambda value for greater than 4 seconds.
Action Taken when the DTC Sets
DTC P2097 is a Type B DTC.
Conditions for Clearing the MIL/DTC
DTC P2097 is a Type B DTC.
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
Diagnostic Aids
The following table illustrates the ECM connector locations:
Circuit/System Verification
1. Ignition ON, observe the scan tool DTC information. Verify DTCs P0137, P0138, or P0140 are not also set.
• If any of the above DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle (Diagnostic Trouble Code Descriptions) for further diagnosis.
Caution: Road test a vehicle under safe conditions and while obeying all traffic laws. Do not attempt any maneuvers that could jeopardize vehicle control. Failure to adhere to these precautions could lead to serious personal injury and vehicle damage.
Important: The rear heated oxygen sensor (HO2S) must be in closed loop for this diagnostic to run. A road load condition is necessary to obtain closed loop.
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. Verify that none of the following conditions exist:
* Inspect the HO2S 1 and HO2S 2 for being secure
* Damaged wiring between either HO2S and the ECM
* Leaking fuel injectors-Refer to Fuel Injector Balance Test with Special Tool (Fuel Injector Balance Test With Special Tool) or Fuel Injector Balance Test with Tech 2 (Fuel Injector Balance Test With Tech 2)
* High fuel system pressure-Refer to Fuel System Diagnosis (Component Tests and General Diagnostics)
* Fuel that is contaminated-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) (Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool))Alcohol/Contaminants-in-Fuel Diagnosis (w/ Special Tool) (Alcohol/Contaminants-In-Fuel Diagnosis (With Special Tool))
* Contaminated HO2S-Silicon
• If you find any of the above conditions, repair as necessary.
2. Ignition OFF, disconnect the harness connector at the HO2S 2.
3. Ignition ON, verify the scan tool HO2S 2 voltage parameter is between 350-550 mV.
• If greater than the specified range, test the HO2S 2 high signal circuit for a short to voltage. If the circuit/connections test normal, replace the ECM.
4. Connect the harness connector at the HO2S 2.
5. Engine idling, raise the engine speed above 1,200 RPM for 30 seconds. Verify the scan tool HO2S 2 voltage parameter is less than 1,050 mV.
• If greater than the specified range, replace the HO2S 2.
6. Engine idling, move the HO2S 1 and HO2S 2 harnesses between the HO2S harness connector and the ECM. Observe the scan tool HO2S 1 lambda parameter, and the HO2S 2 voltage parameter. Verify the parameters do not change abruptly.
• If the parameter changes abruptly, repair the harness/connections as necessary.
7. If all circuits/connections test normal, replace the HO2S 1.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Heated Oxygen Sensor 1 Replacement (Service and Repair)
* Heated Oxygen Sensor 2 Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for engine control module replacement, setup, and programming