The Engine Scan Tool Data Definitions contains a brief description of all engine related parameters available on the scan tool.

APP Sensor 1: The scan tool displays 0-5 volts. The scan tool displays the accelerator pedal position in volts. With the pedal at rest, APP sensor 1 displays about 0.5 volts. At wide open throttle (WOT) APP sensor 1 displays about 5.0 volts.

APP Sensor 2: The scan tool displays 0-5 volts. The scan tool displays the accelerator pedal position in volts. With the pedal at rest, APP sensor 2 displays about 0.25 volts. At wide open throttle (WOT) APP sensor 2 displays about 2.5 volts.

AC Clutch: The parameter indicates On whenever the powertrain control module (PCM) energizes the A/C compressor clutch relay.

AC Request Signal: This parameter indicates whether the A/C switch on the instrument panel (IP) has been selected.

Cam Phase Angle Actual: This parameter indicates the actual camshaft advance in relative degrees. The displayed value is calculated from CMP sensor and CKP sensor inputs. Normal Cam Phase Angle readings are 0 to 4 degrees, where each single degree displayed is approximately equal to 5 degrees of actual camshaft advance.

Cam Phase Angle Desired: This parameter indicates the desired camshaft advance in relative degrees. The PCM determines the desired advance in camshaft timing. On a normal engine this reading will be the same as the Cam Phase Angle.

Cam Phase Angle Variance: This parameter indicates the difference between the Cam Phase Angle and the Cam Phase Angle Desired. This value can be displayed in positive or negative degrees.

Camshaft Phase Solenoid DC: The scan tool range is 0-100 percent. This parameter displays the duty cycle (DC) of the CMP actuator solenoid valve. A reading of less than 20 percent indicates the PCM is retarding camshaft timing. A reading of 20 to 40 percent indicates the PCM is holding the camshaft timing at the current setting. A reading of more than 40 percent indicates the PCM is advancing camshaft timing.

Camshaft Phase Solenoid Command: This parameter indicates whether the powertrain control module (PCM) is controlling the camshaft position (CMP) actuator solenoid valve. The scan tool will display Active when the PCM is commanding the CMP actuator solenoid. A CMP actuator solenoid that is in an Active mode is not necessarily advancing the camshaft phase. Only about 50 percent of the CMP actuator solenoid movement results in advancement of the camshaft phase.

Cruise Control: This parameter indicates whether vehicle speed is controlled by the cruise control system.

Cruise Control Brake Switch: This parameter indicates the state of the cruise brake switch that is controlled by the position of the brake pedal. The normal state of the switch is Applied, CLOSED, when the brake pedal is not released. The cruise brake switch is Released, OPEN, when the brake pedal is depressed.

Cruise Control Resume/Accel Switch: This parameter displays the state of the cruise controls resume/accel switch input to the control module.

Cruise Control Set Spd: This parameter displays the driver requested vehicle speed that the cruise control system is to maintain.

Cruise Control Set/Coast Switch: This parameter displays the state of the cruise controls set/coast switch input to the control module.

Cruise Control Switch: This parameter displays the status of the cruise control switch.

Decel Fuel Cutoff: The Decel Fuel Mode parameter indicates when the powertrain control module (PCM) is operating the fuel injectors in the fuel cut-off mode, the output to the fuel injector is stopped. When the fuel cut-off mode is active the Decel Fuel Mode parameter should read Active. The Decel Fuel Mode parameter should read Inactive during all other fueling conditions.

Diagnostic Mode: Indicates whether the vehicle's diagnostics are operating in Normal mode or in Check mode.

ECT Sensor: The scan tool range is -40 to +140°C (-40 to +284°F). The engine coolant temperature (ECT) sensor is a thermistor which changes internal resistance as the temperature changes. When the sensor is cold, internal resistance high, the powertrain control module (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 PCM interprets the lower voltage as a warm engine.

Engine Load: The scan tool range is 0-100 percent. This parameter indicates the engine load based upon the manifold absolute pressure. The higher the percentage, the more load the engine is under.

Engine Speed: The scan tool range is 0-10,000 RPM. The powertrain control module (PCM) computes engine speed from the ignition reference pulses. The engine speed should remain close to the desired idle under various engine loads with the engine idling.

Engine Speed at Misfire: This parameter represents the engine RPM at the moment that the misfire diagnostic trouble code (DTC) was set.

EVAP Purge Solenoid: This parameter indicates when the evaporative emission (EVAP) canister purge solenoid valve is ON.

EVAP Vacuum Leak Pump: This parameter indicates when the evaporative emission (EVAP) vacuum leak pump is ON or OFF. Normally the pump is turned ON when the EVAP system leak test diagnostic runs. The leak diagnostic runs after the engine has been turned off for 5 hours.

EVAP Vent Solenoid Command: This parameter indicates when the evaporative emission (EVAP) canister vent solenoid valve is Venting. When the EVAP vent solenoid is VENTING, or OFF, the solenoid passage is OPEN. Conversely when the EVAP vent solenoid is NOT VENTING, or ON, the solenoid passage is CLOSED.

Fuel Pump Relay Command: This parameter indicates whether the powertrain control module (PCM) is requesting the fuel pump ON or OFF.

Fuel Tank Pressure Sensor: The scan tool range is 0-5.0 volts. This parameter indicates pressure changes in the fuel tank. When the fuel tank pressure is equal to the barometric pressure, the scan tool display is typically between 3.5-3.8 volts. When the pressure is negative, the voltage decreases, when the pressure is positive, the voltage increases.

High Electrical Load: This mode displays the status of the headlamp switch and the rear defogger switch. If one or more of the switches is ON, a signal is sent to the powertrain control module (PCM) to increase the engine idle speed due to the increased load.

HO2S 1: The scan tool range is 0-5 volts. The heated oxygen (HO2S) 1 is an air/fuel ratio design sensor or wide range oxygen sensor. The HO2S 1 parameter represents the output voltage of the air/fuel ratio oxygen sensor. The voltage should fluctuate within a range of 3.1-3.5 volts. A rich air/fuel mixture, low oxygen content, is indicated when the voltage is less than 3.3 volts. Conversely a lean air/fuel mixture, high oxygen content, is indicated when the voltage is more than 3.3 volts.

HO2S 1 L/R Response Time: The scan tool displays the amount of time the heated oxygen sensor 1 (HO2S 1) requires to switch from lean to rich in milliseconds.

HO2S 1 R/L Response Time: The scan tool displays the amount of time the heated oxygen sensor 1 (HO2S 1) requires to switch from rich to lean in milliseconds.

HO2S 2: The scan tool range is 0-1275 mV. The rear heated oxygen sensor 2 (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.

IAT Sensor: The scan tool range is -40 to +140°C (-40 to +284°F). The powertrain control module (PCM) converts the resistance of the intake air temperature (IAT) sensor to degrees. The PCM uses the intake air temperature (IAT) in order to adjust fuel delivery and spark timing according to incoming air density.

Ign. Cycle Counter: This parameter indicates the total number of times the ignition coils fire for every 1,000 engine revolutions.

Injector #1 Command: The scan tool range is 0 to 32.64 ms. This parameter indicates the amount of time the fuel injector solenoid valve is open.

Load at Misfire: This is Freeze Frame data that is displayed and stored the moment a misfire DTC sets. Load at Misfire is the engine load at which the misfire was set, measured in grams per revolutions.

Long Term FT: The scan tool displays a positive or a negative percentage. The powertrain control module (PCM) derives the Long Term fuel trim (FT) from the Short Term fuel trim value. The Long Term fuel trim represents a long-term correction of fuel delivery. A value of 0 percent indicates that the fuel delivery requires no compensation in order to maintain the PCM commanded air/fuel ratio. A negative value significantly less than 0 percent indicates that the fuel system is rich and the PCM is reducing the fuel delivery, decreasing the fuel injector pulse width. A positive value significantly more than 0 percent indicates that a lean condition exists and the PCM compensates by adding fuel, increasing fuel injector pulse width. Fuel trim values at maximum authority may indicate an excessively rich or lean system.

Loop Status: The Loop Status parameter will display one of the following conditions: OPEN LOOP: The engine has not met all of the conditions necessary for Closed Loop operation. CLOSED LOOP: The powertrain control module (PCM) is using the oxygen sensors as feedback for fuel control.

MAF Sensor: The scan tool range is 0.0-655 g/s. This parameter indicates the quantity of air entering the engine through the mass air flow (MAF) sensor. This volume of air is measured in grams per second (g/s).

MIL Command: This parameter will indicate whether the malfunction indicator lamp (MIL) is illuminated due to a diagnostic trouble code (DTC) being set.

Misfire Current Cyl #1, #2, #3, #4: Indicates a count of the abnormal engine revolutions (misfire) for each cylinder.

Number of DTC(s): Indicates the number of diagnostic trouble codes (DTCs) that are set.

PNP Switch: This parameter indicates the range selection of 3 speed or 4 speed automatic transmission equipped vehicles. The parameter will display Park/Neutral for the Park or Neutral position of the gear selector. The parameter will display In Gear for the Reverse, Drive, or Low positions of the gear selector.

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

Short Term FT: The scan tool displays a positive or a negative percentage. The Short Term fuel trim (FT) represents a short-term correction to fuel delivery by the powertrain control module (PCM). The Short Term FT correction is driven by the fuel control oxygen sensor voltage. When the oxygen sensor (O2S) voltage remains less than 450 mV the PCM adds fuel and the Short Term FT parameter displays a positive percentage. When the oxygen sensor voltage stays at more than 450 mV the PCM subtracts fuel and the Short Term FT parameter displays a negative percentage. During an extended idle in high ambient temperatures the evaporative emission (EVAP) canister may purge, causing the Short Term FT to read in the negative range. This is a normal condition. Fuel trim values at maximum authority may indicate an excessively rich or lean system.

Spark: The scan tool range is -1 to +63 degrees. The scan tool displays the powertrain control module (PCM) controlled value that is being used to control the spark timing.

Starter Switch: This parameter displays ON when the powertrain control module (PCM) is receiving a signal indicating that the engine starter motor is cranking.

TAC Motor: This parameter indicates the status of the TAC motor control. When no TAC system malfunctions are detected, TAC motor operation is normal and scan tool display is Enabled. If a TAC system fault is detected, the TAC motor will be operated in fail-safe mode and the scan tool display is Disabled.

TAC Motor Closed Command: This parameter displays a percentage that momentarily increases when the control module commands the throttle plate to close.

TAC Motor Current: This parameter displays the operating current of the TAC motor.

TAC Motor Open Command: This parameter displays a percentage that momentarily increases when the control module commands the throttle plate to open.

Throttle Plate at Idle: This parameter indicates Yes when the position of throttle body throttle plate is at idle or the default closed position.

TCC Brake Pedal Switch: This parameter is used only on 4 speed automatic transmission equipped vehicles. When the brake pedal is applied, the torque converter clutch (TCC) brake switch sends a signal to the powertrain control module (PCM) in order to disengage the TCC.

TCC Enable Solenoid Command: This parameter is used only on 4 speed automatic transmission equipped vehicles. The TCC Enable Solenoid Command indicates when the powertrain control module (PCM) is requesting the torque converter clutch (TCC) ON.

Total Fuel Trim Average: Total Fuel Trim is a calculated value obtained by combining the Short Term FT and the Long Term FT together. The Total Fuel Trim value indicates how large a correction is necessary in order to keep the air/fuel mixture at the stoichiometrical 14.7:1 ratio. Total Fuel Trim values of + or - 25 percent indicate a fuel system that is operating near the limits of normal fuel control. Total Fuel Trim data is useful in diagnosing fuel system concerns and DTC P0171 or DTC P0172.

Total Misfire Current Count: Indicates a count of the total misfires for all the cylinders.

TP Sensor: The scan tool range is 0-100 percent. The scan tool displays the amount of throttle opening in percentage. At closed throttle the scan tool displays 8-12 percent. At wide open throttle (WOT) the scan tool displays approximately 80 percent. The TP sensor value is determined by the input from the TP sensor 1 that is located in the throttle actuator control (TAC) module.

TP Sensor 2: The scan tool range is 0-5 volts. The scan tool displays changes in throttle plate position. The TP sensor 2 value is determined by the input from the TP sensor 2 that is located in the throttle actuator control (TAC) module.

Vehicle Speed Sensor: The scan tool range is 0-255 km/h (0-158 mph). This parameter displays the vehicle speed. The powertrain control module (PCM) receives reference pulses from the vehicle speed sensor (VSS) and converts the pulses into km/h and mph for display.