Fuel System > Engine Control System > P2196 O2 Sensor Signal Stuck Rich (Bank 1 Sensor 1)

Component Location

General Description

In order to control emissions of the CO, HC and NOx components of the exhaust gas, heated oxygen sensor (HO2S), mounted on the front side and rear side of catalytic converter, detects the oxygen content in the exhaust gas. The front HO2S signal is used to control air/fuel ratio (closed loop fuel control) and the rear HO2S signal is used to monitor front HO2S and catalyst for proper operation. The HO2S requires a minimum temperature to operate properly and provide a closed loop fuel control system. The HO2S contains the heater element to reduce its warming-up time and ensure its performance during all driving conditions. The oxygen sensor generates a voltage that indicates the difference between the oxygen content of the exhaust stream and the oxygen content of ambient air. When the exhaust stream is “rich,” there is more oxygen in the ambient air than in the exhaust stream, so the voltage will be higher.

DTC Description

Checking output signals from HO2S under detecting condition, if HO2S's signal is rich during fuel cut-off conditions, PCM sets P2196. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycles.

DTC Detecting Condition

Item

Detecting Condition

Possible cause

DTC Strategy

•	Monitor HO2S's signal

•	Poor Connection

•	Faulty HO2S

•	Faulty PCM

EnableConditions

•	Battery voltage ≥ 10V

•	Engine running ≥ 60sec.

•	Power Enrichment conditions

•	Engine warm-up state

•	Not in Transient Conditions

Threshold value

•	HO2S's signal > 0.42V

DiagnosisTime

•	Continuous (More than 8 sec. failure for every 9 sec. Test)

MIL On Condition

•	2 Driving Cycles

Specification

Test Condition	HO2S Voltage(Sensor1)	HO2S Voltage(Sensor2)
HO2S Signal at idle after warm-up	Signal is normally switching from rich to lean more than 3 times in 10 sec.	Signal is normally above 0.6V.
HO2S signal at open circuit(Pumping current OFF)	Approx. 0.45V
HO2S signal at open circuit(Pumping current ON)	Approx. 3.5V

Schematic Diagram

Signal Wavefrom And Data

After warming-up, if accelerator pedal is released suddenly around 4000rpm, the HO2S signal reading will be lower than 200mV resulting from Fuel cut-off for the moment. Conversely, if suddenly accelerator pedal is depressed, HO2S signal reading will be around 0.6V ~1.0V. At idle, Normally HO2S signal will switch from lean to rich with 3 Hz. At higher engine RPM, the switching frequency increases.

Monitor DTC Status

Check DTC Status

(1)	Connect scantool to Data Link Connector(DLC).

(2)

IG "ON".

(3)	Select "DTC" button, and then Press "DTC Status" to check DTC's information from the DTCs menu.

(4)	Read "DTC Status" parameter.

(5)

Is parameter displayed "Present fault"?

	▶ Go to "Component Inspection" procedure.
	▶ Fault is intermittent caused by poor contact in the sensor's and/or PCM's connector or was repaired and PCM memory was not cleared. Thoroughly check connectors for looseness, poor connection, ending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.

Component Inspection

Check the condition of HO2S

(1)	Check HO2S for poor connection or loose terminal.

(2)	Check if HO2S is ensurely installed.

(3)

Are the conditions of HO2S normal ?

	▶ Go to "Check the Signal waveform of HO2S" as follows.
	▶ Repair it and then go to "Verification of Vehicle Repair" procedure.

Check the Signal waveform of HO2S

(1)	IG "OFF" and connect HO2S connector.

(2)	Engine start.

(3)	After warming-up, monitor signal waveform of HO2S with scantool.

(4)

Is the sensor switching properly?

	▶ Substitude with a known-good PCM and check for proper operation. If the problem is corrected, replace PCM and go to "Verification of Vehicle Repair" procedure.
	▶ Substitute with a known - good HO2S and check for proper operation. If the problem is corrected, go to "Verification of Vehicle Repair" procedure.

There is a memory reset function on scantool that can erase optional parts automaticallydetected and memorized by PCM. Before or after testing PCM on the vehicle, use this function before reusing the PCM

Verification Of Vehicle Repair

After a repair, it is essential to verify that the fault has been corrected.

1.	Connect scantool and select "DTC" button.

2.	Press "DTC Status" button and confirm that "DTC Readiness Flag" indicates "Completed". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions

3.	Read "DTC Status" parameter

Is parameter displayed "History(Not Present) fault"?

	▶ System performing to specification at this time. Clear the DTC
	▶ Go to the applicable troubleshooting procedure.