Typical Scan Tool Data Values Part 2

Scan Tool Data Definitions
Not all parameters will apply to each vehicle. Use only the parameters which apply to your particular vehicle.

1-2 Solenoid - (ON/OFF): The scan tool indicates whether this shift solenoid in the automatic transmission is commanded ON by the VCM.

2-3 Solenoid - (ON/OFF): The scan tool indicates whether this shift solenoid in the automatic transmission is commanded ON by the VCM.

3-2 Downshift Solenoid - (ON/OFF): The scan tool indicates whether this shift solenoid in the automatic transmission is commanded ON by the VCM.

4WD - (Enable/Disable): The scan tool indicates enabled when four wheel drive has been selected by the operator.

4WD Low - (Enable/Disable): The scan tool indicates enabled when four wheel drive low has been selected by the operator.

A/C Evaporator Switch - (Open/Closed): The A/C Evaporator Switch is an input to the VCM that determines when pressure has reached a calibrated threshold. The VCM uses this switch as the primary input for determining when to command the A/C compressor ON or OFF.

Scan Tool Data Display
A/C Sec. High Pres. Switch - (Open/Closed): The Secondary High Press. Switch closes when the A/C systems high pressure limit is approached. The VCM monitors the state of this switch for compressor and auto recirculation operation. The switch closes at a high pressure value which is calibrated for specific platforms. The VCM continuously monitors the secondary high pressure switch when A/C has been selected by the operator.

A/C Relay - (ON/OFF): The scan tool indicates whether the A/C relay control circuit has been commanded ON by the VCM. The A/C relay provides power to control the A/C compressor clutch. It will indicate YES when the relay is commanded ON.

A/C Request - (Yes/No): The scan tool indicates the state of the A/C request input circuit. The VCM uses the A/C request signal in order to determine whether A/C compressor operation has been requested by the operator.

Actual EGR Position - Range (0 - 100%): The Actual EGR Position indicates the actual EGR valve pintle position as a percentage. A fully closed valve would be displayed as 0%.

Air Fuel Ratio - Range (0.0:1 - 25.5:1): The scan tool indicates the VCM calculated air to fuel ratio. The typical air to fuel ratio is 14.7:1.

Auto Recirculation - (ON/OFF): If the Secondary High Pressure switch closes, indicating high refrigerant pressures, auto recirculation will be commanded ON by the VCM. This will prevent warm outside air from entering the vehicle which might further raise the A/C refrigerant pressures.

Barometric Pressure (BARO) - Range (0 - 5 Volts): The BARO represents a measurement of the barometric air pressure. This measurement is determined by using the Manifold Air Pressure (MAP) sensor in order to determine manifold vacuum. This function is performed when the Ignition is selected from OFF to ON, and during high throttle angle operations when manifold pressure equals ambient barometric pressure. This parameter is scaled in volts which is the raw output from the MAP sensor prior to being converted by the VCM to kPa.

Barometric Pressure (BARO) - Range (62 kPa - 104 kPa): The VCM calculates the displayed BARO parameter from the MAP sensor when the ignition is selected from OFF to ON and at WOT conditions. The BARO parameter represents local ambient barometric pressure. The VCM uses the displayed BARO reading in order to compensate engine fueling differences for changes in altitude. This parameter is scaled in kilo pascals (k/pa).

Brake Switch - Range (Applied/Released): The Brake Switch indicates the status of the brake switch. Applied would indicate the brake pedal has been depressed.

Closed Loop (CL) Since Restart - (Yes/No): The Closed Loop Since Restart indicates whether or not the vehicle has been in a closed loop state during the current Ignition cycle.

Clutch Pedal Switch - (Applied/Released): The scan tool indicates the current clutch switch state. When the clutch pedal is applied, the clutch switch will indicate ON.

CMP Retard - Range (0- 90 degrees): The CMP Retard indicates a correction to the CMP sensor and the CKP sensor relationship caused by small tolerance variations or component misalignment.

Cruise - (Enable/Disable): The Cruise parameter indicates if the driver has requested cruise control.

Cycles of Misfire Data - Range (0 - 100): Displays an increasing count of crankshaft revolutions from 0 to 100. It will reset to 0 after reaching 100.

Decel Fuel Mode - (Active/Inactive): The scan tool indicates whether the vehicle is in decel fuel cutoff mode. This mode is generally entered during long decels to prevent catalyst overheating and excessive tailpipe emissions.

Desired EGR Position - Range (0 - 100%): The Desired EGR Position indicates the desired EGR pintle position in a percentage. 0% indicates a closed EGR valve. 100% is a fully opened EGR valve.

Desired IAC Position - Range (0 - 255) Counts: The desired IAC Position indicates how much the IAC valve is commanded open by the VCM. 0 counts would indicate a commanded fully closed valve. 255 counts would indicate a commanded fully opened valve.

Desired Idle Speed - Range (0 - 3, 187 RPM): The VCM commands the Desired Idle Speed by controlling the IAC. The VCM compensates for various engine loads by controlling IAC in order to maintain the desired idle speed.

DTC Set this Ignition - (Yes/No): The scan tool indicates whether or not any DTC has set during the current ignition cycle.

ECT - Range (-40 to 215 °C (-40 to 419 °F)): The Engine Coolant Temperature (ECT) sensor is mounted in a coolant passage in the intake manifold. The VCM monitors the engine temperature as the ECT sensor responds to temperature changes in the engines coolant.

ECT Sensor - Range (0 - 5 Volts): The Engine Coolant Temperature (ECT) sensor is mounted in a coolant passage in the intake manifold. The VCM monitors the engine temperature as the ECT sensor responds to temperature changes in the engines coolant. This parameter is scaled in volts and is the raw voltage from the ECT detected by the VCM on the signal circuit.

EGR Duty Cycle - Range (0-100%): The EGR Duty Cycle determines the percentage of time the EGR valve's control circuit has 12 volts applied to it. This is a method to control the current applied to the valve motor. As duty cycle increases, so does current which forces the valve to open further and allow more exhaust gas to enter the intake. 100% duty cycle would indicate a fully opened valve.

EGR Sensor - Range (0 - 5 Volts): The EGR Sensor indicates the actual EGR pintle position, as detected by the VCM, scaled in voltage. A low voltage indicates a closed valve.

Engine Load - Range (0 - 100%): The VCM determines the engine load based upon the engine speed and MAF sensor readings. Engine Load increases with any increase in RPM and/or airflow.

Engine Run Time - Range (0:00:00 - 18:12:15) Hours:Minutes:Seconds: The Engine Run Time is a measure of how long the engine has run during this ignition cycle. When the engine stops running, the timer resets to zero.

Engine Speed - Range (0 - 16, 384 RPM): The VCM computes the Engine Speed from the CKP sensor input.

EVAP Canister Purge - (OFF/ON): The EVAP Canister Purge pulls a small vacuum on the entire evaporative emission system. The scan tool displays if the EVAP Canister Purge Solenoid Valve is currently OFF or ON. When the scan tool displays ON, manifold vacuum is being applied to the system.

EVAP Duty Cycle - Range (0 - 100%): The scan tool indicates the EVAP duty cycle that the VCM is commanding. The EVAP duty cycle is a pulse width modulated voltage applied to the purge valve which is displayed as a percentage. A high percentage of EVAP duty cycle would indicate near maximum canister purging.

EVAP Vent Solenoid - (Closed/Open): The scan tool will show the status of the EVAP Vent Solenoid. A closed EVAP Vent Solenoid would indicate the Evaporative System is being tested for leaks.

Excess Vacuum Test - (Pass/Not Run/Fail): The Excess Vacuum Test will Fail if fuel tank vacuum builds at an excessive rate during normal EVAP canister purge. A restricted vent valve or vent valve hoses will cause improper venting. The scan tool display states for this parameter are Pass and Not Run/Fail.

Fuel Level - Range (0 - 100%): The scan tool indicates as a percentage the level of fuel in the fuel tank.

As the senders float position changes, the Fuel Level sensors signal voltage changes. The VCM converts this voltage into a percentage of fuel remaining in the fuel tank.

Fuel Level Sensor - Range (0 - 5 Volts): The scan tool will display the Fuel Level Sensor signal voltage which varies with fuel level.


Fuel Tank Pressure - Range (-20 to 7 in H2O): The scan tool displays the vapor pressure measured in the fuel tank by the Fuel Tank Pressure Transducer. The VCM converts the raw voltage signal from the sensor into a pressure scale displayed by the scan tool.

Fuel Trim Cell - Range (0 - 22) Cell: 22 separate cells contain MAP and RPM values from a range of engine operating conditions. Each cell determines fuel requirements for a specific operating condition that the engine is running within. Examples would be idling, accelerations, road load cruise, or decelerations.

Fuel Trim Enable - (YES/NO): This parameter indicates when the VCM is using fuel trim values to adjust fuel delivery to the engine. Fuel trim will be disabled when the vehicle is not in closed loop, malfunction codes related to fuel trim are set, large amounts of purge vapor are ingested by the engine, or additional diagnostics that temporarily affect fuel trim operation are active.

HO2S BN 1 Sen. 1 - Range (0 - 1 Volts): The HO2S BN 1 Sen. 1 indicates the voltage activity of the HO2S (Bank 1 Sensor 1).

HO2S BN 1 Sen. 2 - Range (0 - 1 Volts): The HO2S BN 1 Sen. 2 indicates the voltage activity of the HO2S (Bank 1 Sensor 2).

HO2S BN 1 Sen. 3 - Range (0 - 1 Volts): The HO2S BN 1 Sen. 3 indicates the voltage activity of the HO2S (Bank 1 Sensor 3).

HO2S BN 2 Sen. 1 - Range (0 - 1 Volts): The HO2S BN 2 Sen. I indicates the voltage activity of the HO2S (Bank 2 Sensor 1).

HO2S BN 2 Sen. 2 - Range (0 - 1 Volts): The HO2S BN 2 Sen. 2 indicates the voltage activity of the HO2S (Bank 2 Sensor 2).

HO2S Xcounts Bn 1 - Range (0 - 255): The HO2S Xcounts Bn 1 increments each time that the HO2S (Bank 1 Sensor 1) crosses the 450 MV threshold. This number resets to zero after it reaches it limit of 255.

HO2S Xcounts Bn 2 - Range (0 - 255): The HO2S Xcounts B2 increments each time that the HO2S (Bank 2 Sensor 1) crosses the 450 MV threshold. This number resets to zero after it reaches it limit of 255.
IAC Position - Range (0 - 255) Counts: The scan tool displays in counts the Idle Air Control (IAC) pintle position commanded by the VCM. The greater the number of counts, the larger the air passage opening. The Idle Air Control should respond fairly quickly to changes in engine load in order to maintain desired idle RPM.

Intake Air Temperature (IAT) - Range (40 to 151 °C (40 to 303 °F)): The VCM converts the signal voltage of the Intake Air Temperature (IAT) sensor into degrees. The VCM uses the intake air temperature in order to adjust fuel delivery and spark timing according to the incoming air temperature.

Intake Air Temperature (IAT) Sensor - (0 - 5 Volts): The VCM monitors the Intake Air Temperature (IAT) sensor for voltage changes. This parameter displays the raw voltage signal detected by the VCM. The VCM uses the intake air temperature in order to adjust fuel delivery and spark timing according to the incoming air temperature.

Ignition 1 - Range (0.0 - 25.5 Volts): The Ignition 1 parameter indicates the voltage level on the Ignition input to the VCM. The normal Ignition 1 voltage is approximately 13.8 volts, but may vary between 11 - 16 volts.

Ignition 1 Low - (Yes/No): The scan tool indicates when low ignition voltage has been detected by the VCM A low Ignition 1 voltage may degrade ignition timing and injector operation. The normal ignition 1 voltage is approximately 13.8 volts, but may vary between 11 - 16 volts.

Ignition 1 High - (Yes/No): The scan tool indicates when high ignition voltage has been detected by the VCM. An excessively high ignition 1 voltage could damage electronics and electrical components. The normal ignition 1 voltage is approximately 13.8 volts, but may vary between 11 - 16 volts.

Ignition 1 ON - (Yes/No): The Ignition 1 On parameter indicates when the VCM is detecting Ignition voltage. The normal Ignition voltage is approximately 13.8 volts, but may vary between 11 - 16 volts. The VCM monitors the Ignition voltage to compensate for low voltage operation of the injectors and to increase the dwell time of the ignition coil.