BI-Fuel/Alternative Fuels
CIRCUIT DESCRIPTIONThe Heated Oxygen Sensor (HO2S) is used in order to determine the oxygen content of the engine's exhaust. The oxygen content of the exhaust indicates when the engine is operating lean or rich. When the engine is operating lean, the exhaust will have more oxygen content. Once at operating temperature, the HO2S will produce a voltage in relation to the oxygen content of the exhaust. The HO2S requires an operating temperature of 360°C (600°F) to produce voltage. The HO2S will produce more voltage when the exhaust is rich and less voltage when the exhaust is lean. The HO2S operating voltage range is between 0.1 volts (100 mV) to 1 volt (1,000 mV).
The gasoline Control Module (VCM/PCM or ECM) supplies a bias (or reference) voltage to the HO2S. This bias voltage is around 450 mV.
This DTC is used to indicate an HO2S signal voltage that is below the normal operating range of the sensor.
CONDITIONS FOR RUNNING THE DTC
^ The engine is operating on alternative fuel.
^ The engine speed is more than 400 RPM.
^ The Engine Coolant Temperature (ECT) is above 70°C (160°F).
^ The Alternative Fuels ECM determines the HO2S has been at operating temperature for at least 30 seconds. Operating temperature is indicated when engine coolant temperature is more than 40°C (104°F) AND desired gas flow is greater than 0.3 grams per second for 30 seconds.
^ The Alternative Fuels ECM is operating in Closed Loop fuel control.
CONDITIONS FOR SETTING THE DTC
The Alternative Fuels ECM monitors an HO2S signal voltage of less than 0.08 volts (78 mV) for 15 seconds continuously.
ACTION TAKEN WHEN THE DTC SETS
The Alternative Fuels ECM will Control fuel trim based upon the Bank 2 Sensor 1 signal. If a Bank 2 Sensor 1 DTC sets, the Alternative Fuels ECM will operate in Open Loop fuel control.
^ A first failure of this DTC will NOT illuminate the MIL and will store as Last Test Failed but not as History.
^ The Alternative Fuels ECM will illuminate the MIL and store the DTC as History after 2 consecutive drive trips that the diagnostic runs and fails.
^ The Alternative Fuels ECM will record operating conditions at the time the DTC sets. This information will be stored as Freeze Frame data.
CONDITIONS FOR CLEARING THE MIL/DTC
^ The Last Test Failed status will clear when the DTC runs and passes.
^ The Alternative Fuels ECM will turn OFF the MIL after 3 consecutive drive trips that the DTC runs and passes.
^ The History status will clear after 40 consecutive WARM-UP cycles with NO failures of ANY DTC.
^ All DTC Information can be cleared using a scan tool.
^ Interruption of Control Module (AF ECM/VCM/PCM or ECM) power or ground MAY clear DTC Information. Clearing DTC Information with this method is in-consistent and should not be performed.
DIAGNOSTIC AIDS
Intermittent Condition
A fault not present indicates the condition that caused the DTC to set is intermittent and not currently present. Refer to the Intermittent Conditions diagnostic information located in Symptoms - Computers and Control Systems. If any additional DTCs were stored proceed to the applicable DTC table in the order stated in Diagnostic System Check - Alternative Fuels (Computers and Control Systems). Initial Inspection and Diagnostic Overview Intermittent Conditions
TEST
