EVAP Data

[1][2]EVAP Data

Engine Speed - Range (0-16384 RPM): The VCM computes the Engine Speed from the fuel control reference input. The speed should remain close to the desired idle under the various engines loads with the engine idling.

Desired Idle Speed - Range (0-3187 RPM): The VCM commands the desired AC. The VCM compensates for various engine loads in order to maintain the desired idle speed.

Throttle Position (TP) Sensor - Range (0.0-5.0 volts): The VCM uses the Throttle Position in order to determine the amount of throttle demanded by the operator of the vehicle. The TP sensor reads between 0.360.96 volts at idle to above 4.0 volts at Wide Open Throttle (WOT).

TP Angle - Range (0-100%): The VCM computes the TP Angle from the TP signal voltage input. The TP Angle should read 0% at idle. AT 0%, the TP voltage will read below 0.90 volts. The TP Angle should read 100% at Wide Open Throttle.

ECT - Range -40°-215°C (-4O°-419°F): The Engine Coolant Temperature (ECT) sensor is mounted in the intake the intake manifold. The ECT sends the engine temperature information to the VCM. The VCM supplies 5 volts to the ECT sensor circuit. The sensor is a thermistor which changes the internal resistance as the temperature changes. When the sensor is cold meaning the internal resistance is high, the VCM monitors a high voltage signal. The VCM interprets the high voltage signal as a cold engine. As the sensor warms meaning the internal resistance decreases, the voltage signal decreases. The VCM interprets the lower resistance as a warm engine.

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

Manifold Absolute Pressure (MAP) Sensor - Range (0.0-5.0 volts): The MAP sensor produces a low signal voltage when the manifold pressure is low. A low manifold pressure means a high vacuum. The MAP sensor produces a high signal voltage when the manifold pressure is high. A high manifold pressure means a low vacuum. With the ignition ON and the engine stopped, the manifold pressure equals the atmospheric pressure causing the signal voltage to be high. The VCM uses this information as an indication of the vehicle's altitude. This information is referred to as the BARO. Comparison of this BARO reading with a known good vehicle with the same sensor is a good way to check accuracy of a suspect sensor. The readings should read the same +0.4 volt.

Manifold Absolute Pressure (MAP) - Range (10 kPa-104 kPa): The Manifold Absolute Pressure (MAP) sensor measures the change in the intake manifold pressure from the engine load and the speed changes. As the intake manifold pressure increases, the air density in the intake manifold also increases. Additional fuel is required.

Barometric Pressure (BARO) - Range (0.0-5.0 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 the manifold vacuum. Since the barometric air pressure depends on the altitude, the measurement may vary from 100 kPa (sea level) to 60 kPa (14,000 ft).

Barometric Pressure (BARO) Sensor - Range (0 kPa-62 kPa): The VCM determines the displayed BARO reading from the MAP sensor at the ignition ON and the engine OFF and the WOT conditions. The BARO reading displayed represents the barometric pressure. The VCM uses the displayed BARO readings in order to compensate for the altitude differences.

MAF - Range (0-512 g/s): The VCM converts the Mass Air Flow sensor input signal into grams per second. The MAF indicates the amount of air entering the engine.

EVAP Canister Purge - (ON/OFF): 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, the small vacuum is being applied.

[1][2]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 modulated signal which is translated into a direct percentage of the maximum commandable state.

[1][2]EVAP Vent Solenoid - (Closed/Open): The scan tool will show the status of the EVAP Vent Solenoid.

Fuel Tank Pressure - (-20 to 7 in. H2O): The scan tool indicates the current fuel tank pressure that is converted by the VCM using the fuel tank pressure sensor signal voltage. As pressure decreases a greater vacuum is created.

Excess Vacuum Test - (Pass/Not R/F): The Excess Vacuum Test will fail if the 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.

Weak Vacuum Test - (Pass/Not R/F): The Weak Vacuum Test only runs if the Loaded Canister Test does not pass. Insufficient vacuum build up during normal purge operation with the vent valve closed will cause this test to fail.

Small Leak Test - (Pass/Not R/F): The Small Leak Test runs immediately after the Weak Vacuum Test. The EVAP system is closed and the fuel tank vacuum is monitored by the VCM. A high loss of vacuum rate will cause this test to fail. This test may run up to three times before reporting a failure.

Purge Leak Test - (Pass/Not R/F): The Purge Leak Test runs only after a cold start occurred during the current ignition and the Weak Vacuum Test did not fail. The VCM commands both the purge and vent valves closed. If a vacuum builds, then the restricted or inoperative vent valve will cause this test to fail.

Fuel Level - Range (0-100%): The scan tool indicates the current percentage of fuel tank occupancy. The float position changes the value of a variable resistor who's voltage the VCM converts to the displayed percentage.

Fuel Level Sensor - (0.0-2.9 Volts): The scan tool will display the voltage coming from the Fuel Level Sensor which will vary from.39 volts to 2.9 volts.

Rich/Lean Bn 1 - (Rich/Lean): The Rich/Lean Bn 1 indicates the condition of the exhaust gases in bank 1.

Rich/Lean Bn 2 - (Rich/Lean): The Rich/Lean Bn 2 indicates the condition of the exhaust gases in bank 2.

Loop Status - Range (Open Loop/Closed Loop): The scan tool indicates whether the vehicle is in an open or closed loop state. The VCM uses HO2S information for determining fuel delivery during closed loop.

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.

Fuel Trim Cell - Range (0-22) Cell: The Fuel Trim Cell is dependent upon the engine speed and the MAP sensor readings. A plot of the RPM vs the MAP sensor readings. A plot of the RPM vs the MAP is broken into 22 cells. The Fuel Trim Cell indicates which cell is currently active.

Knock Adjust Factor - Range (-90° to 9O°): The knock sensor is a piezoelectric device which detects vibration due to spark knock. The VCM converts the knock sensor signal according to calibrated values; thus allowing the engine to operate at optimum spark advance with out knock to improve driveability and fuel economy.

Engine Run Time - Range (0:00:0-18:12:15) 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.