by Yanks0114 » Fri Oct 01, 2004 2:19 pm
Found this, not sure if its relevant or not
The heated oxygen sensor (HO2S) is a sensor designed to create a voltage relative to the oxygen content in the engine exhaust stream. The control module supplies the HO2S with signal high and low circuits. Ignition voltage and ground are supplied to the HO2S heater by independent circuits. The oxygen content of the exhaust indicates when the engine is operating lean or rich. When the HO2S detects that the engine is operating rich, the signal voltage is high, and decreases the signal voltage as the engine runs leaner. This oscillation above and below the bias voltage, sometimes referred to as activity or switching, can be monitored with the HO2S signal voltage.
The HO2S contains a heater that is necessary in order to quickly warm the sensor to operating temperature. The heater also maintains the operating temperature during extended idle conditions. The HO2S needs to be at a high temperature in order to produce a voltage. When the HO2S reaches operating temperature, the control module monitors the HO2S bias, or reference, voltage. It also monitors the HO2S signal voltage for Closed Loop fuel control. During normal Closed Loop fuel control operation, the control module will add fuel, or enrich the mixture, when the HO2S detects a lean exhaust content. The control module will subtract fuel, or "lean-out" the mixture, when the HO2S detects a rich exhaust condition.
Certain vehicle models utilize an oxygen sensor behind the catalytic converter in order to monitor catalyst efficiency.
This diagnostic trouble code (DTC) determines if the HO2S is functioning properly. It checks for an adequate number of HO2S voltage transitions above and below the bias range of 300-600 mV. This DTC sets when the vehicle control module (VCM) fails to detect a minimum number of voltage transitions above and below the bias range during the test period. Possible causes of this DTC are:
An open or a short to voltage on either the HO2S signal or HO2S low circuits
A malfunctioning HO2S
A problem in the HO2S heater or its circuit
A faulty HO2S ground
Conditions for Running the DTC
No active TP sensor DTCs
No active EVAP system DTCs
No active IAT sensor DTCs
No active MAP sensor DTCs
No active ECT sensor DTCs
No active MAF sensor DTCs
No active misfire DTCs
No intrusive tests (i.e., EGR or Catalyst) in progress
No device control in progress
The system voltage is between 11.7-18 volts
DTCs P0131, P0132, P0134, and P0135 not active
The system is in closed loop
The ECT is greater than 57°C (135°F)
The engine has been running for more than 75 seconds
The MAF is between 15-55 g/s
The engine speed is between 1100-3000 RPM
EVAP canister purge active
The above conditions are present for more than 2 seconds
Conditions for Setting the DTC
The number of lean-to-rich and rich-to-lean transitions within a 100 second sample period were less than a calibrated number
Action Taken When the DTC Sets
The VCM turns the MIL (Malfunction Indicator Lamp) ON after 2 consecutive test failures.
The VCM records the operating conditions at the time the diagnostic fails. The Freeze Frame and Failure Records store this information.
Conditions for Clearing the MIL or DTC
The control module turns OFF the MIL after 3 consecutive drive trips when the test has run and passed.
A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70°C (158°F) during the same ignition cycle.
Use a scan tool in order to clear the DTCs.
Diagnostic Aids
Important
Never solder the HO2S wires. For proper wire and connector repairs, refer to Wiring Repairs or Connector Repairs in Wiring Systems.
Check for the following conditions:
An improperly installed air intake duct
The air intake duct for collapsed ducting, restrictions, or a missing or plugged air filter
Throttle body and intake manifold vacuum leaks
A damaged or blocked throttle body inlet
Exhaust system for corrosion, leaks, or loose or missing hardware. Refer to Exhaust System Inspection in Engine Exhaust.
The HO2S is installed securely and the pigtail harness is not contacting the exhaust manifold or wires
HO2S contamination
The vacuum hoses for splits, kinks, and proper connections
Excessive water, alcohol, or other contaminants in the fuel. Alcohol/Contaminants-in-Fuel Diagnosis .
VCM sensor grounds that are clean, tight, and properly
