[amidgeha]

O2 Sensor Signal Biased/Stuck Rich

The Engine Control Module (ECM) uses the heated oxygen sensor information to regulate the air-fuel ratio close to a stoichiometric ratio. This maximizes the catalytic converter’s ability to purify the exhaust gas. The sensor detects oxygen levels in the exhaust gas and sends this signal to the ECM. The inner surface of the sensor element is exposed to outside air. The outer surface of the sensor element is exposed to exhaust gas. The sensor element is made of platinum coated zirconia and includes an inte- grated heating element. The heated oxygen sensor has the characteristic whereby its output voltage changes suddenly in the vicinity of the stoichiometric air-fuel ratio. The heated oxygen sensor generates output voltage between 0 V and 1.0 V in response to the oxygen concentration in exhaust gas. When the output voltage of the heated oxygen sensor is 0.55 V or more, the ECM judges that the air-fuel ratio is RICH. When it is 0.4 V or less, the ECM judges that the air-fuel ratio is LEAN. Under normal condition, the output voltage from the heated oxygen sensor alternates RICH and LEAN sides periodically. If the heated oxygen sensor outputs RICH signal (or LEAN signal) constantly, or if the heated oxygen sensor cannot output enough voltage to reach the minimum specification, the ECM interprets this as a malfunction in the heated oxygen sensor and sets a DTC.

Cause:
Faulty Front Heated Oxygen Sensor Bank 1
Front Heated Oxygen Sensor Bank 1 harness is open or shorted
Front Heated Oxygen Sensor Bank 1 circuit poor electrical connection
Inappropriate fuel pressure
Faulty fuel injectors
Intake air leaks may be faulty
Vacuums leaks

Symptoms:
Check engine light
Excessive Fuel Consumption