P2197

DTC P2197 - HO2S SIGNAL BIASED LEAN

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.

DTC DESCRIPTORS
This diagnostic procedure supports the following DTCs:
- DTC P2195 HO2S Signal Biased Lean Bank 1 Sensor 1
- DTC P2197 HO2S Signal Biased Lean Bank 2 Sensor 1

CONDITIONS FOR RUNNING THE DTC

Condition 1 and 2
- Before the ECM can report DTC P2195 or P2197 failed, DTCs P0137, P0138, P0140, P0141, P0157, P0158, P0160, P0161, P2270, P2271, P2272, and P2273 must run and pass.
- The front and rear heated oxygen sensors are at operating temperature.
- The rear HO2S voltage signal is more than 850 mV.
- The front HO2S is more than 1.08 lambda.
- The Loop Status for both the front and rear sensors is Closed Loop.
- DTC P2195 and P2197 run continuously once the above conditions are met.

CONDITIONS FOR SETTING THE DTC

Condition 1
- The ECM detects that the front HO2S is operating too lean while the rear HO2S is operating too rich and the ECM detects that the fuel trim is at maximum control. OR
- The rear fuel trim, long and short term, is more than a threshold.
- This DTC sets after the air flow coming into the engine accumulates to more than 200 grams and the above conditions are met for more than 4 seconds.

Condition 2
- The ECM detects that the rear HO2S is operating too rich while the ECM is commanding a lean air/fuel mixture.
- This DTC sets after the air flow coming into the engine accumulates to more than 800 grams and the above condition is met for more than 4 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) at the beginning of the fourth ignition cycle, after 3 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 and related Freeze Frame data clears after 40 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
- Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.
- The lower connector of the ECM is connector C1 and the upper connector of the ECM is connector C2. Refer to Engine Controls Component Views.
- For an intermittent condition, refer to Intermittent Conditions. Intermittent Conditions

TEST DESCRIPTION

Step 1 - Step 9:

Step 10 - Step 20:

The numbers below refer to the step numbers on the diagnostic table.
2. This step determines if a condition exists.
5. This step is testing for a rear HO2S sensor circuit condition. A circuit condition sets this DTC.
8. This step is testing for an intermittent circuit condition. Thoroughly inspect the HO2S circuits for an intermittent circuit condition.
9. This step is testing for an intermittent circuit condition. Thoroughly inspect the HO2S circuits for an intermittent circuit condition. DTC P2195 or P2197 HO2S Signal Biased Lean