The Engine Scan Tool Data Definitions contains a brief description of all engine related parameters available on the scan tool. The list is arranged in the order shown on the scan tool.

Engine Speed: Scan Tool Range 0-10,000 RPM. The ECM/PCM computes Engine speed from the ignition reference pulses. The Engine speed should remain close to desired idle under various engine loads with the engine idling.

Desired Idle Speed: The Desired Idle Speed is an ECM/PCM internal parameter which indicates the ECM/PCM requested idle. If the engine is not running, this number is not valid.

ECT: The Scan Tool Range -40°C-120°C (-40°F-250°F). The ECT sensor is a thermistor which changes internal resistance as temperature changes. When the sensor is cold (internal resistance high), the ECM/PCM monitors a high signal voltage and interprets the voltage as a cold engine. As the sensor warms (internal resistance decreases), the voltage signal decreases and the ECM/PCM interprets the lower voltage as a warm engine.

IAT: Scan Tool Range -40°C to 120°C (-40°F to 250°F). The ECM/PCM converts the resistance of the intake air temperature sensor to degrees. The ECM/PCM uses the intake air temperature (IAT) in order to adjust fuel delivery and spark timing according to incoming air density.

Engine Load: Scan tool range 0% to 100%. This parameter indicates engine load based on manifold absolute pressure. The higher the percentage, the more load the engine is under.

MAP: Scan Tool Range 0-125 kPa/0.0-5.0 volts. The manifold absolute pressure (MAP) sensor measures the change in the intake manifold pressure from engine load, and speed changes. As intake manifold pressure increases, the intake vacuum decreases resulting in a higher kPa reading.

BARO: Scan Tool Range 0-125 kPa. The barometric pressure (BARO) sensor measures the changes in atmospheric pressure. This parameter will read approximately 95 to 105 kPa at sea level.

MAF: This parameter indicates the quantity of air entering the engine through the sensor in grams per second.

TP Sensor: The scan tool displays 0-5 volts. The scan tool displays the amount of throttle opening in volts. Closed throttle displays about 1 volt and wide open throttle displays about 3.5 volts.

TP Angle: The scan tool displays 0-100%. The scan tool displays the amount of throttle opening in percentage. Closed throttle displays 0% and wide open throttle displays near 100%.

IAC Duty Cycle: The parameter indicates the opening of the by-pass air passage in terms of percentage. The opening of the by-pass air passage determines the amount of air flowing through the by-pass air passage and is controlled by the IAC motor.

Throttle Position Level: The scan tool displays 0 to 7 counts. This parameter indicates the throttle opening in counts and is used by the automatic transmission for determing shift points.

Closed Throttle Position Switch: This parameter will read Idle when the throttle valve is closed, and Not Idle when the throttle valve is opened. The Closed Throttle Position Switch is part of the TP sensor.

HO2S 1: Scan Tool Range 0-1275 mV. The HO2S 1 parameter represents the fuel control exhaust oxygen sensor output voltage. The voltage should fluctuate constantly within a range between 10 mV (lean exhaust) and 1000 mV (rich exhaust) while operating in Closed Loop.

HO2S 2: Scan Tool Range 0-1275 mV. The rear HO2S 2 represents the exhaust oxygen output voltage beyond the catalytic converter. This voltage will remain inactive or appear lazy within a range 100 mV (lean exhaust) and 900 mV (rich exhaust) when the system is operating in Closed Loop.

Loop Status: The scan tool displays Open or Closed. Closed Loop indicates that the ECM/PCM is controlling fuel delivery according to oxygen sensor voltage. Open Loop indicates that the ECM/PCM ignores the oxygen sensor voltage and bases the amount of fuel to be delivered on the TP sensor, the ECT sensor, and MAP sensor inputs.

HO2S 1 Ready: A yes display indicates that the oxygen sensor is warmed up and is capable of sending useful voltage readings to the ECM/PCM. No display indicates a cold (not ready) oxygen sensor.

HO2S 2 Ready: A yes display indicates that the oxygen sensor is warmed up and is capable of sending useful voltage readings to the ECM/PCM. No display indicates a cold (not ready) oxygen sensor.

Short Term FT: The scan tool displays Percentage. The Short Term Fuel Trim represents a short-term correction to fuel delivery by the ECM/PCM in response to the amount of time the fuel control oxygen sensor voltage spends above or below the 450 mV threshold. If the oxygen sensor voltage mainly remains less than 450 mV, indicating a lean air/fuel mixture, short term fuel trim increases into the positive range above 0%. The ECM/PCM adds fuel. If the oxygen sensor voltage stays mainly above the threshold, the short term fuel trim decreases below 0% into the negative range. The ECM/PCM reduces the fuel delivery in order to compensate for the indicated rich condition. Under certain conditions such as an extended idle and a high ambient temperature, the canister purge may cause the Short Term Fuel Trim to read in the negative range during normal operation. The Fuel trim values at maximum authority may indicate an excessively rich or lean system.

Short Term FT: The scan tool displays Counts. The Short Term Fuel Trim represents a short-term correction to fuel delivery by the ECM/PCM in response to the amount of time the fuel control oxygen sensor voltage spends above or below the 450 mV threshold. If the oxygen sensor voltage mainly remains less than 450 mV, indicating a lean air/fuel mixture, short term fuel trim increases into the range above 128. The ECM/PCM adds fuel. If the oxygen sensor voltage stays mainly above the threshold, the short term fuel trim decreases below 128 into the range. The ECM/PCM reduces the fuel delivery in order to compensate for the indicated rich condition. Under certain conditions such as an extended idle and a high ambient temperature, the canister purge may cause the Short Term Fuel Trim to read in the negative range during normal operation. The Fuel trim values at maximum authority may indicate an excessively rich or lean system.

Long Term FT: The scan tool displays Percentage. The ECM/PCM derives the Long Term Fuel Trim from the Short Term Fuel Trim value. The Long Term Fuel Trim represents a long-term correction of fuel delivery. A value of 0% indicates that fuel delivery requires no compensation in order to maintain the ECM/PCM commanded air/fuel ratio. A negative value significantly below 0% indicates that the fuel system is rich and the ECM/PCM is reducing the fuel delivery (decreased injector pulse width). A positive value significantly greater than 0% indicates that a lean condition exists and the ECM/PCM compensates by adding fuel (increased injector pulse width). Fuel trim values at maximum authority may indicate an excessively rich or lean system.

Long Term FT: The scan tool displays Counts. The ECM/PCM derives the Long Term Fuel Trim from the Short Term Fuel Trim value. The Long Term Fuel Trim represents a long-term correction of fuel delivery. A value of 0% indicates that fuel delivery requires no compensation in order to maintain the ECM/PCM commanded air/fuel ratio. A value significantly below 128 indicates that the fuel system is rich and the ECM/PCM is reducing the fuel delivery (decreased injector pulse width). A value significantly greater than 128 indicates that a lean condition exists and the ECM/PCM compensates by adding fuel (increased injector pulse width). Fuel trim values at maximum authority may indicate an excessively rich or lean system.

Total Fuel Trim: The value of the Total Fuel Trim is obtained by putting values of short Term Fuel Trim and Long Term Fuel Trim together. this value indicates how much correction is necessary to keep the air/fuel mixture stoichiometrical.

Injector PWM: This parameter indicates the time of the fuel injector valve opening.

Fuel Cutoff Signal: When the fuel is being cut, output signal to the fuel injector is stopped, the parameter should read on, but when fuel is not in the cut off mode the parameter should read off.

Spark: Scan tool range -1 to 60 degrees. This displays the ECM/PCM controlled value that is being used to control the spark timing.

Spark Advance Adjust Test Switch: When the Duty Check Data Link Connector Test Switch Terminal (terminal 5) is grounded this parameter will display On and the ignition timing will be fixed at base.

EVAP Duty Cycle: Scan tool range 0% to 100%. The EVAP Duty Cycle specifies the EVAP Canister Purge Valve ON (valve open) time rate within a certain set cycle. Zero percent means that the purge valve is completely closed while a 100% is a fully open valve.

EVAP Vent Solenoid: This parameter indicates when the ECM/PCM is turning ON the EVAP Canister Vent Solenoid.

EVAP Density Trim: Scan tool range 0 to 128 counts. This parameter indicates EVAP system purge concentration and is indicated in counts.

Fuel Level: Scan tool range 0 to 100%. This parameter indicates approximate fuel level in the fuel tank. The detectable range of the fuel level sensor is set as 0 to 100%, however, with some models whose fuel tank capacity is smaller, the indicated fuel level may be only 70% even when the fuel tank is full.

Fuel Tank Pressure: This parameter indicates the pressure in the fuel tank and is expressed with respect to the barometric pressure. When the fuel tank pressure is equal to the barometric pressure, the scan tool indicates 0 in. H2O.

Fuel Tank Pressure Control Solenoid: The EVAP Tank Pressure Control Solenoid Vacuum Valve is Open when the valve is turned ON by the ECM/PCM and Closed when the valve is turned OFF. The

EGR Sol. Vacuum Valve: This parameter indicates when the ECM/PCM is turning ON the EGR Solenoid Vacuum Valve.

EGR Bypass Solenoid: This parameter indicates when the ECM/PCM is turning ON the EGR Bypass Solenoid

Air Conditioning: The parameter will indicate On whenever the A/C Idle-Up signal is received by the ECM/PCM from the A/C compressor control module. This will allow the ECM/PCM to adjust the engine idle to maintain acceptable engine performance.

Fuel Pump: This parameter indicates that the ECM/PCM is turning ON the fuel pump by turning ON the fuel pump relay. The ECM/PCM will turn the fuel pump relay ON for three seconds when the ignition is turned ON and turn the fuel pump relay ON continuously when receiving reference pulses from the ignition module.

Power Steering Switch: The scan tool will display an On signal whenever the steering wheel is turned right or left far enough to increase the power steering fluid pressure above a specified amount. This will allow the ECM/PCM to adjust the engine idle to maintain acceptable engine performance.

Starter Switch: This parameter displays On when the ECM/PCM is receiving a signal indicating that the engine starter motor is cranking.

Battery Voltage: This parameter indicates battery positive voltage inputted from the Main Relay to the ECM/PCM.

Charging Efficiency: When the rate of charge to the battery from the alternator is high, the percentage will be greater.

PNP: This parameter indicates the automatic transmission range selection. The parameter will display P - N for the park or neutral position of the gear selector and R - D - L for the reverse, drive or low positions of the gear selector.

Vehicle Speed: Scan tool range 0-200 km/h/0-125 MPH. This parameter displays the vehicle speed. The Powertrain Control Module (ECM/PCM) receives reference pulses from the Vehicle Speed Sensor (VSS) and converts them into km/h and MPH for display.

TCC Solenoid: This parameter indicates when the ECM/PCM is requesting the automatic transmission TCC On.

Monitor TCC Solenoid: This parameter indicates that the TCC request signal from the ECM/PCM was recieved by the transmission.

Overdrive Switch: This parameter indicates when the overdrive selection switch located on the A/T shift lever is On.

Mode Select Switch: The scan tool displays the A/T operation mode as selected by the vehicle operator. The Power mode is indicated when the transmission shift selection is made for optimum performance under high loads (hill climbing, towing). The Normal mode is indicated when economical transmission shifting is selected. The normal mode should be selected for most driving conditions.