User guide

AutoEnginuity ScanTool User Guide 53
severity of the fault determines whether this is a "One-Trip" or
"Two-Trip" monitor.
Fuel System Status
This system status indicates whether the fuel system is open or
closed. Typically, when the vehicle starts, the fuel system is open.
When the oxygen sensors warm up and start reporting stably, the
fuel system is closed.
Fuel Trim
Feedback adjustments to the base fuel schedule. Short-term fule
trim refers to dynamic or instantaneous adjustments. Long-term
fuel trim refers to much more gradual adjustments to the fuel cali-
bration schedule than short-term adjustments. Long-term adjust-
ments compensate for vehicle differences and gradual changes that
occur over time.
General Circuit Malfunction
Fixed value or no response from the system.
Heated Catalyst Monitor
A non-continuous monitor that checks the efficiency of the way the
catalytic converter heats up. If this monitor does not complete,
check the oxygen sensor heaters, air injection system, and the cata-
lytic converter. This is a "Two-Trip" monitor.
HO2S or Heated Oxygen Sensor
An oxygen sensor that is electrically heated to decrease the time it
takes for the oxygen sensor reach operating temperature. See Oxy-
gen Sensor.
High Input
Circuit voltage, frequency, or other signal measured at the control
module input terminal or pin, that is at or near full scale for the par-
ticular signal being measured. It is measured with the external cir-
cuit, component, or system connected.
IAC or Idle Air Control Motor
This is a motor, or sometimes a valve, that controls how the engine
idles.