This list explains each data message displayed on the Tech 1 scan tool.

Engine Speed: Range 0-16384 RPM. Engine speed is computed by the PCM from the fuel control reference input. The speed should remain close to desired idle with the engine idling.

Desired Idle: Range 0-3187 RPM. The idle speed that is commanded by the PCM. The PCM will compensate for various engine loads in order to maintain the engine at the desired idle speed.

ECT: Range -40°C to 215°C (-40°F to 419°F). The Engine Coolant Temperature (ECT) sensor sends engine temperature information to the PCM. The PCM supplies five volts to the engine coolant temperature sensor circuit. The sensor is a thermistor which changes internal resistance as the temperature changes. When the sensor is cold (internal resistance is high), the PCM monitors a high voltage which the PCM interprets as a cold engine. As the sensor warms (internal resistance decreases), the voltage signal decreases and the PCM interprets the low voltage as a warm engine.

MAP: Range 11-105 kPa, 0-5.0V. The Manifold Absolute Pressure (MAP) sensor measures the intake manifold pressure. Manifold pressure changes with the engine speed and the engine load. The PCM uses manifold absolute pressure in order to adjust the fuel delivery and the spark timing.

BARO: Range 11-105 kPa, 0-5.0V. The Barometric Pressure (BARO) sensor measures the change in the intake manifold pressure, which results from altitude changes. This value is updated at ignition run and also at Wide Open Throttle (WOT).

TP Sensor: Range 0-5.0V. The Throttle Position (TP) sensor is used by the PCM to determine the amount of throttle demanded by the operator of the vehicle. The TP sensor reads between 0.36-0.96V at idle to above 4V at WOT.

TP Angle: Range 0-100%. The Throttle Position (TP) angle is computed by the PCM from the TP sensor voltage input. TP angle is 0% at idle (TP voltage is below 0.90V) and TP angle is 100% at WOT.

Ignition Volts: Range 0-25.5V. This represents the system voltage measured by the PCM at the ignition feed circuit.

Loop Status: Displays Open or Closed. CLOSED LOOP displays when the PCM is controlling the fuel delivery as close to an air/fuel ratio of 14.7 to 1 as possible. This ratio is determined by the Oxygen Sensor voltage.

Engine Run Time: Range 0:00:00-18:12:15 (hours:minutes:seconds). A measure of how long the engine has been running. When the engine stops running, the timer is reset to zero.

# of Curr. DTCs: Range 0-255. This indicates the total number of current Diagnostic Trouble Codes (DTCs) which have been set.

A/C Request: Displays Yes or No. This indicates whether the HVAC selector is requesting the Air Conditioning (A/C). The input is received by the Instrument Panel Cluster (IPC) and then the signal is sent over UART serial data to the PCM, and finally the signal is sent to the scan tool over class 2 serial data.

Cruise Engaged: Displays Yes or No. This signal indicates whether the cruise control system is in control of vehicle speed. The signal is sent to the PCM from the cruise control module. The PCM changes the transmission shift calibrations and turns On an indicator lamp on the Instrument Panel Cluster (IPC) (when equipped).

TCC Enable: Displays Yes or No. This parameter is the commanded PCM state of the TCC solenoid Valve. Yes indicates a commanded energized state. No indicates a commanded non-energized state. This commanded state occurs at various vehicle speeds.

TCC Slip Speed: Range -6375 to +6375 RPM. The Torque Converter Clutch (TCC) Slip Speed displays the amount of slippage in RPM between the engine and the transmission output shaft.

Trans OSS: Range 0-8192 RPM. The Vehicle Speed Sensor (VSS) assembly indicates the rotational speed of the transmission output shaft expressed as revolutions per minute.

TCC Brake Switch: Displays OFF or ON. When the brake pedal is applied, the Torque Converter Clutch (TCC) brake switch opens. This interrupts the voltage signal to the PCM which disengages the TCC and disables cruise control.

Trans. Range: Displays Park/Reverse/Neutral/Drive 3/Drive 2/Low/Invalid. The scan tool displays the decoded position of the transmission range switch (PRNDL). This information is then sent to the Instrument Panel Cluster (IPC) and is displayed to the operator.

MPH km/h: Range 0-255 mph, 0-255 km/h. The VSS assembly signal is converted into metric or English units for display. The vehicle speed output from the PCM is 4000 pulses per mile. The scan tool uses the class 2 serial data from the PCM in order to obtain vehicle speed. The instrument panel cluster, the cruise control module, and the multi-function alarm module use the 4000 ppm output.