Circuit Description
The bank 1 sensor 2 or bank 2 sensor 2 heated oxygen sensor (HO2S) output signal is used by the engine control module (ECM) when calculating the oxygen storage capacity (OSC) of the three-way catalytic converter (TWC). The ECM can also use each HO2S voltage signal to calculate the air-fuel ratio that results in the most efficient operation of the TWC. This accomplished by minor fuel trim corrections, rich or lean, based on the output signal received from the HO2S. The ECM will adjust the air-fuel ratio in an attempt to keep the bank 1 sensor 2 and bank 2 sensor 2 output signals near 600 mV. If the ECM continues to make a rich fuel trim correction for longer than a calibrated time, in an effort to drive the post sensor near 600 mV in response to a lean engine operating condition, DTC P2096 will set for bank 1 or DTC P2098 will set for bank 2.
DTC Descriptor
This diagnostic procedure supports the following DTCs:
| • | DTC P2096 Post Catalyst Fuel Trim System Low Limit Bank 1 |
| • | DTC P2098 Post Catalyst Fuel Trim System Low Limit Bank 2 |
Conditions for Running the DTC
| • | DTCs P0030, P0031, P0032, P0036, P0037, P0038, P0050, P0051, P0052, P0056, P0057, P0058, P0101, P0102, P0103, P0106, P0107, P0108, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0131, P0132, P0135, P0137, P0138, P0139, P0140, P0141, P0151, P0152, P0155, P0157, P0158, P0159, P0160, P0161, P0201-0208, P0300, P0301-P0308, P0442, P0443, P0446, P0449, P0453, P0454, P0455, P0458, P0459, P0496, P2231, P2234, P2237, P2240, P2243, P2247, P2251, P2254, P2626, P2629 are not set. |
| • | The canister purge is in a steady state. |
Conditions for Setting the DTC
The ECM has commanded the fuel trim greater than 2.93 percent for more than 24 seconds out of a 25 second monitoring period.
OR
The affected bank HO2S 2 voltage is less than 151 mV for more than 75 seconds.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
| • | Carefully inspect for any exhaust leaks between the upstream and downstream sensor of the affected bank. |
| • | The most likely cause for this DTC is a deteriorated or contaminated HO2S 1. |
| • | Depending on the state of the HO2S deterioration, this code may not reset, or may be very difficult to reset. |
| • | If the HO2S deterioration is significant enough, other HO2S DTCs may set or be present in concurrence with this DTC. |
| • | Attempt to compare the activity of both the affected bank HO2S 1 and HO2S 2 to the known good bank using the live plot feature of the scan tool. Operate the vehicle under various load and vehicle/engine speed conditions. Look for any indication of improper operation or contamination of the affected bank HO2S 1 or HO2S 2. |
| • | For an intermittent condition, refer to Intermittent Conditions . |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Engine Control Module Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 3 | |
2 | If DTC P1137 or P1157 are also set, diagnose those DTCs first. Is DTC P1137 or P1157 also set? | -- | Go to DTC P1137 or P1157 | Go to Step 3 |
3 | Cycle the throttle from idle to wide open throttle (WOT) 3 times within 5 seconds while observing the HO2S Bank 1 Sensor 2 or HO2S Bank 2 Sensor 2 parameter with a scan tool. Does the voltage react immediately to the above action? | -- | Go to Step 4 | Go to Step 5 |
4 |
Did the DTC fail this ignition? | -- | Go to Step 5 | Go to Diagnostic Aids |
5 |
Is the voltage less than the specified value? | 25 mV | Go to Step 6 | Go to Step 7 |
6 |
Is the voltage less than the specified value? | 25 mV | Go to Step 2 of DTC P0135 or P0155 | Go to Step 8 |
7 | Test the HO2S high signal circuit for an open or high resistance. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 9 |
8 | Test the HO2S low signal circuit for an open or high resistance. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 9 |
9 | Test for an intermittent and for a poor connection at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 10 |
10 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 11 | -- |
11 |
Did the DTC fail this ignition? | -- | Go to Step 3 | Go to Step 12 |
12 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
