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SECONDARY AIR (Secondary Air System Status - PCM output)
Display: UPSTR, DNSTR, ATMSP
The secondary air injection system on newer vehicles is controlled by the PCM.
The PCM use actuators to control this pollution control system. Secondary air can be
added the exhaust system near the exhaust manifold (before any catalytic converts),
at the catalytic convert(s) or not at all.
UPSTR - UP STREAM the PCM is demanding that secondary air be added at the
exhaust manifolds
DNSTR - DOWN STREAM the PCM is demanding secondary air to added at the
catalytic converter
ATMSP - ATMOSPHERE the PCM is demanding no secondary air to be added,
because the air pump can not be turned off the air will simply be dumped to the
outside air (Atmosphere).
ST FL TRM 1 (%) (Short-term Fuel Trim Bank 1/2 - PCM calculated value)
ST FL TRM 2 (%)
Display: Positive (rich fuel trim) or Negative (lean fuel trim) Percentage
This value represents the short-term correction of the fuel metering on a fuel-
injected engine. The ST Trim indicates whether the PCM is commanding a rich or
lean fuel mixture for the engine. The SF Trim number can range from -100% to
+100%, with the midpoint being 0. A positive ST Trim reading indicates that the PCM
has commanded a short-term rich mixture correction in response to a lean operating
condition. A negative ST Trim reading indicates that the PCM has commanded a
short-term lean mixture in response to a rich operating condition. Fuel Trim is
adjusted by varying the fuel injector pulse widths.
Short-term Fuel Trim corrections operate only in closed loop mode. In open loop
mode, the number usually defaults to a 0 (fixed value). Depending on the vehicle, the
ST Trim values may be reset to the default of 0 every time the engine is shut off, or
corrected values may be retained in computer memory. Retained values are reapplied
when the vehicle is restarted. All values are erased when the battery is disconnected.
Some PCMs are able to control the left and right cylinder bank Fuel Trim individu-
ally, shown by the ST TRIM1 & 2 parameters.
TROUBLE CODE (Trouble Code - PCM value)
Display: any code possible of causing a freeze frame capture
The Trouble Code parameter will give you the diagnostic trouble code that caused
a freeze frame capture. This information is helpful in diagnosing the cause of a
driveability. If no freeze frame data has been captured this PID will be zero.
VEH SPEED (KPH) (Vehicle Speed Sensor - PCM input)
VEH SPEED (MPH)
Display: numeric speed indication (kph or mph)
This is a value calculated by the PCM using electric pulses from the Vehicle Speed
Sensor to determine actual vehicle speed, expressed in either miles per hour (mph)
or kilometers per hour (kph). The PCM uses the vehicle speed measurements
primarily for torque converter clutch engagement and electronic cruise control
systems. Vehicles not equipped with automatic transmissions or cruise control may
not have a Vehicle Speed Sensor. The OBD II System Tester may display a Vehicle
Speed value, but it should always be 0.