Engine 1 Data

Engine Scan Tool Data Definitions
This information will assist you in tracking down emission or driveability problems since the displays can be viewed while the vehicle is being driven. Refer to the Powertrain OBD System Check for additional information. Testing and Inspection

Engine Speed - Range 0 - 16384 RPM: Engine Speed is determined by the VCM from the 4X Crankshaft position sensor. It should remain close to the desired idle under various engine loads with the engine idling.

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

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

Start Up ECT - Range -40°C to 215°C (40°F to 41°F): When the engine is started the engine coolant temperature is recorded by the VCM. This information is used to calculate the time to closed loop.

ECT Sensor - Range (0 - 5.0V): The Engine Coolant Temperature (ECT) sensor is mounted in the intake manifold and sends engine temperature information to the VCM. The VCM supplies 5V to the ECT sensor circuit. The sensor is a thermistor which changes internal resistance as temperature changes. When the sensor is cold (internal resistance high), the VCM monitors a high voltage signal which it interprets as a cold engine. As the sensor warms (internal resistance decreases), the voltage signal will decrease and the VCM will interpret the lower voltage as a warm engine.

Intake Air Temperature (IAT) Sensor - Range (0 - 5.0V): The VCM converts the resistance of the Intake Air Temperature (IAT) sensor to degrees. Intake air temperature is used by the VCM to adjust fuel delivery and spark timing according to incoming air density.

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

Air Fuel Ratio - Range (0:1 - 25.5:1): Indicates the air fuel ratio based on Oxygen sensor (HO2S) inputs. The VCM uses fuel trim to adjust fueling to attempt to maintain an air fuel ratio of 14.7:1. A lower number indicates a richer air fuel mixture while a higher number indicates a leaner mixture.

Manifold Absolute Pressure (MAP) Sensor - Range (0 - 5.0V): The MAP sensor produces a low signal voltage when manifold pressure is low (high vacuum) and a high voltage when the pressure is high (low vacuum). With the ignition ON and the engine stopped, the manifold pressure is equal to atmospheric pressure causing the signal voltage to be high. This information is used by the VCM as an indication of vehicle altitude and is referred to as 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. Readings should be the same ±4V.

Barometric Pressure (BARO) - Range (0 - 5.0V): The BARO represents a measurement of barometric air pressure that is determined by using the Manifold Air Pressure (MAP) sensor to determine manifold vacuum. Since barometric air pressure depends on altitude, it may vary from 100 kPa (sea level) to 60 kPa (14,000 ft.)

Manifold Absolute Pressure (MAP) - Range (10 kPa - 104 kPa): 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 air density in the intake manifold also increases and additional fuel is required.

Barometric Pressure (BARO) Sensor - Range (0 kPa - 62 kPa): The BARO reading displayed is determined from the MAP sensor at ignition ON, engine OFF, and WOT conditions. The BARO reading displayed represents barometric pressure and is used to compensate for altitude differences.

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

TP Angle - Range (0 - 100%): The TP Angle is computed by the VCM from the TP signal voltage input. TP Angle should read 0% at idle (TP voltage below 0.90V) and read 100% at Wide Open Throttle (WOT).

Long Term Fuel Trim FT BN 1 - Range (0 - 255 ) (-100% - 100%): Long Term Fuel Trim (FT) is derived from the short term fuel trim value and is used for long-term correction of fuel delivery. A value of 128 counts (0%) indicates that fuel delivery requires no compensation to maintain a 14.7:1 air/fuel ratio. A value below 128 counts means that the fuel system is too rich and fuel delivery is being reduced (decreased injector pulse width). A value above 128 counts indicates that a lean condition exists and the VCM is compensating by adding fuel (increased injector pulse width).

Long Term Fuel Trim FT BN 2 - Range (0 - 255) (-100% - 100%): Long Term Fuel Trim (FT) is derived from the short term fuel trim value and is used for long-term correction of fuel delivery. A value of 128 counts (0%) indicates that fuel delivery requires no compensation to maintain a 14.7:1 air/fuel ratio. A value below 128 counts means that
the fuel system is too rich and fuel delivery is being reduced (decreased injector pulse width). A value above 128 counts indicates that a lean condition exists and the VCM is compensating by adding fuel (increased injector pulse width).

Short Term Fuel Trim FT BN 1 - Range (0 - 255) (-100% - 100%): Short term fuel trim (formerly fuel integrator) represents a short-term correction to fuel delivery by the VCM in response to the amount of time the HO2S voltage spends above or below the 450 mV threshold. If the HO2S voltage has mainly been below 450 mV, indicating a lean air/fuel mixture, short term fuel trim will increase to tell the VCM to add fuel. If the HO2S voltage stays mainly above the threshold, the VCM will reduce fuel delivery to compensate for the indicated rich condition.

Short Term Fuel Trim FT BN 2 - Range (0 - 255) (-100% - 100%): Short term fuel trim (formerly fuel integrator) represents a short-term correction to fuel delivery by the VCM in response to the amount of time the HO2S voltage spends above or below the 450 mV threshold. If the HO2S voltage has mainly been below 450 mV, indicating a lean air/fuel mixture, short term fuel trim will increase to tell the VCM to add fuel. If the HO2S voltage stays mainly above the threshold, the VCM will reduce fuel delivery to compensate for the indicated rich condition.

FT Cell BN 1 - Range (0 - 255): Fuel Trim Cell is dependent upon engine speed and MAP sensor readings. A plot of RPM vs. MAP is broken down into 22 cells. Fuel Trim Cell indicates which cell is currently active.

FT Cell BN 2 - Range (0 - 255): Fuel Trim Cell is dependent upon engine speed and MAP sensor readings. A plot of RPM vs. MAP is broken down into 22 cells. Fuel Trim Cell indicates which cell is currently active.

IAC Position - Range (0 - 255): The Idle Air Control (IAC) pintle position commanded from the VCM is displayed in counts. The greater the number of counts, the greater the command idle speed (air passages opened). Idle air control should respond fairly quickly to changes in engine load to maintain desired idle RPM.

Desired IAC - Range (0 - 255): This indicates the desired IAC position.

Knock (KS) Sensor Activity - Range (0 - 255) Counts: Indicates the amount of spark knock detected by the VCM.

Knock (KS) Sensor - Range (0 - 5.0V): This indicates the amount of engine knock detected in volts.

Spark Advance - Range (-96 to -255°): This is a display of the spark advance calculation which the VCM is programming into the ignition system. It computes the desired spark advance using data such as engine temperature, RPM, load, vehicle speed and operating mode.

KS Retard - Range (0 - 90°): This indicates the amount of spark advance being removed to diminish spark knock.

Cam Retard: This indicates the difference between the CMP sensor and the CKP sensor in degrees.

Engine Load - Range 0 - 100%: This indicates the engine load based on Manifold Absolute Pressure. The higher the percentage, the more load the engine is under.

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

DTC Counter - Range (0 - 255): This indicates the total number of current Diagnostic Trouble Codes (DTCs) set. This does not necessarily mean the Malfunction Indicator Lamp (MIL) is illuminated.

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