P2096
DTC P0172 or P2096 (LUW)
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
DTC P0172
- Fuel Trim System Rich
DTC P2096
- Post Catalyst Fuel Trim System Low Limit
Circuit/System Description
The engine control module (ECM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Fuel delivery is controlled differently during open loop and closed loop. During open loop, the ECM determines fuel delivery based on sensor signals without heated oxygen sensor (HO2S) input. During closed loop, the ECM adds heated oxygen sensor (HO2S) inputs and level of purge to calculate the short and long term fuel trim adjustments. If the heated oxygen sensor (HO2S) indicates a lean condition, the fuel trim values will be above 0%. If the heated oxygen sensor (HO2S) indicates a rich condition, the fuel trim values will be below 0%. The short term fuel trim values change rapidly in response to the heated oxygen sensor (HO2S) voltage signals. The long term fuel trim makes rough adjustments in order to maintain an air/fuel ratio of 14.7:1.
The heating elements inside each heated oxygen sensor (HO2S) heat the sensor to bring the sensor up to operating conditions faster. This allows the system to enter closed loop earlier and the control module to calculate the air to fuel ratio sooner.
The HO2S utilizes the following circuits:
* A signal circuit
* A low reference circuit
* An ignition voltage circuit
* A heater control circuit
Conditions for Running the DTC
P0172
* P0030, P0053, P0102, P0103, P0106, P0107, P0108, P0116, P0117, P0118, P0131, P0132, P0133, P0134, P0135, P015A, P015B, P1133, P0201, P0202, P0203, P0204, P0300, P0301, P0302, P0303, P0304, P0443, P0449, P0452, P0453, P0455, P0496 are not set.
* The loop status parameter indicates closed.
* The engine coolant temperature (ECT) is between -20 to +130°C (-4 to +266°F).
* The intake air temperature (IAT) is between -20 to +150°C (-4 to +302°F).
* The manifold absolute pressure (MAP) is between 18-253 kPa (2.61-37 PSI).
* The engine speed is between 400-6 100 RPM.
* The barometric pressure (BARO) is more than 70 kPa (10 PSI).
* DTCs P0172 and P2096 run continuously when the above conditions have been met.
P2096
* The ignition is ON.
* The evaporative emission (EVAP) system is not purging.
* The post catalyst fuel trim is enabled.
* This DTC P2096 runs continuously when the above conditions have been met.
Conditions for Setting the DTC
P0172
* The long term fuel trim weighted average value is more or less than a calibrated value.
* The above condition is present for approximately 3 min after the conditions for running the DTC have been met.
P2096
The long term fuel trim has reached its limit while the heated oxygen sensor (HO2S) voltage is still trying to move the adjustment further in the same direction.
Action Taken When the DTC Sets
DTCs P0172 and P2096 are Type B DTC.
Conditions for Clearing the DTC
DTCs P0172 and P2096 are Type B DTC.
Diagnostic Aids
DTC P0172: Determines if the fuel control system is in a rich condition, based on the filtered long-term fuel trim metric.
DTC P2096: Determines if the post catalyst O2 sensor based fuel control system has been unable to adapt to a lean exhaust gas condition for too long.
A failed HO2S will not cause DTC P2096 to set without the occurrence of circuit related HO2S DTCs. Do not replace an HO2S to address this DTC.
Reference Information
Schematic Reference
Engine Controls Schematics (LUW) [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Sunshade - Left (D6I)
Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References Control Module References for scan tool information
Circuit/System Verification
Note: Disregard any transmission symptoms, antilock brake system (ABS) indicators, and traction control system indicators until any fuel trim faults are repaired. A fuel trim fault may cause default actions such as harsh shifts and illumination of the ABS/traction control system indicators.
1. Verify that other DTCs are not set.
• If any DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.
2. Allow the engine to reach operating temperature. With the engine running, observe the scan tool HO2S Sensor 1 parameter. The HO2S 1 value should vary from approximately 40 mV to approximately 900 mV, and respond to fueling changes.
3. The normal scan tool Short Term Fuel Trim parameter should be between +10 to -10%, with near 0% the optimum, with the engine running at operating temperature.
4. The scan tool Long Term Fuel Trim parameter should be between +10 to -10%, with near 0% the optimum, with the engine running at operating temperature.
5. 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: Allow the engine to reach operating temperature. With the engine running, observe the scan tool Long Term Fuel Trim parameter with a scan tool. The value should be less than approximately 18% with the engine running at operating temperature.
If the value is not less than -25%, inspect for the following:
* With the ignition ON and the engine OFF, observe the scan tool HO2S Sensor 1 parameter. The scan tool MAP Sensor pressure should be within the range specified for your altitude. Refer to Altitude Versus Barometric Pressure Altitude Versus Barometric Pressure.
• If the MAP sensor does not indicate the correct barometric pressure, refer to DTC P0106, P0107, or P0108 (LUW) P0106.
* With the engine idling and the transmission in the park or neutral position, observe the scan tool MAP Sensor parameter. The scan tool MAP Sensor parameter should be between 19-42 kPa (2.8-6.1 PSI).
• If the scan tool MAP Sensor parameter is not between 19-42 kPa (2.8-6.1 PSI), refer to DTC P0106, P0107, or P0108 (LUW) P0106.
* Vacuum hoses for kinks, and improper connections
* The air intake duct for being collapsed or restricted
* The air filter for being dirty or restricted
* Objects blocking the throttle body
* Excessive fuel in the crankcase due to leaking fuel injectors
* The evaporative emissions control system for improper operation
* Excessive fuel pressure. Refer to Fuel System Diagnosis Fuel System Diagnosis.
* Malfunctioning fuel injectors. Refer to Fuel Injector Diagnosis Fuel Injector Diagnosis.
* Fuel contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis Testing and Inspection.
* The HO2S for improper installation and for electrical wires or connectors that may have contacted the exhaust system
* The B52A Heated Oxygen Sensor 1 sensor 1 signal circuit open, shorted to ground, or shorted to the low reference circuit
* The B52A Heated Oxygen Sensor 1 sensor 1 low signal circuit for an open circuit or high resistance
Repair Instructions
* Air Cleaner Assembly Replacement (LDE, LXV, LUW, 2H0 and LFH) Service and Repair
* Air Cleaner Element Replacement (1.6L LDE, LXV, 1.8L 2H0, LUW and LFH) Service and Repair
* Evaporative Emission Canister Replacement Service and Repair
* Fuel Injector Replacement Service and Repair
* Fuel Tank Fuel Pump Module Replacement (1.8L 2H0 and LUW) Fuel Tank Fuel Pump Module Replacement
* Fuel System Cleaning Service and Repair
* Heated Oxygen Sensor Replacement - Sensor 1 (LDE, LXV, LUW, 2H0) Heated Oxygen Sensor Replacement - Sensor 1
* Manifold Absolute Pressure Sensor Replacement (1.8L 2H0 and LUW) Service and Repair
* Throttle Body Assembly Replacement (1.6L LDE, LXV, 1.8L 2H0, and LUW) Removal and Replacement
Repair Verification
Note: After repairs, use the scan tool fuel trim reset function in order to reset the long term fuel trim.
1. Install any components or connectors that have been removed or replaced during diagnosis.
2. Perform any adjustment, programming, or setup procedures that are required when a component or module is removed or replaced.
3. Turn ON the ignition, with the engine OFF.
Note: Do not clear codes with the engine running. The codes may reset in the same ignition cycle.
4. Clear the DTCs.
5. Turn OFF the ignition for 60 s.
6. Start the engine.
7. Duplicate the conditions for running the DTC and use the freeze frame/failure records, if applicable, in order to verify the DTC does not reset. If the DTC resets, or another DTC is present, refer to the Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle and perform the appropriate diagnostic procedure.
8. To verify that the performance of the catalyst has not been affected by the condition that set this DTC, perform the Repair Verification for DTC P0420. Refer to DTC P0420 (LUW) P0420.