Engine Data

ECT - Range: 4000 - 12000 The Engine Coolant Temperature (ECT) sensor is a thermistor (a variable resistor that changes with the temperature) in series with a fixed resistor in the Powertrain Control Module (PCM). The PCM provides a 5 volt reference voltage to the ECT sensor. The PCM reads the voltage across the ECT sensor and calculates this voltage reading into a temperature reading. A low voltage reading at the PCM indicates a hot engine and a high voltage reading at the PCM indicates a cold engine.


IAT - Range: 4000 - 12000 The Intake Air Temperature (IAT) sensor is a thermistor (a variable resistor that changes with the temperature) in series with a fixed resistor in the Powertrain Control Module (PCM). The PCM provides a 5 volt reference voltage to the IAT sensor. The PCM reads the voltage across the IAT sensor and calculates this voltage reading into a temperature reading in order to control the air/fuel mixture and the spark timing. A low voltage reading at the PCM indicates that the intake air is warm and a high voltage reading at the PCM indicates that the intake air is cold.

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

Closed Throttle Switch: This parameter will read Idle when the ISC motor plunger becomes in contact with the throttle, or Not Idle when the ISC motor plunger is apart from the throttle lever.

ISC Duty Cycle - Range: 20% to 40%: The parameter indicates the opening of the throttle valve by the ISC actuator in a measure of percentage. The ISC duty percentage will increase when the PCM commands a larger throttle valve opening and will decrease when the ISC actuator responds to a PCM command for a smaller throttle valve opening.

Engine Speed - Range: 0- 9999 RPM The engine speed is calculated by the Powertrain Control Module (PCM) from the ignition reference pulses that are received from the Camshaft Position (CMP) sensor. The PCM will keep this value close to the desired idle under various engine loads with the engine idling.

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

Short Term FT - Range: -0 to 255 The Short Term Fuel Trim (FT) represents a short term correction to the fuel delivery by the PCM in response to the amount of time that the oxygen sensor voltage spends above or below the 450mV threshold. If the oxygen sensor has mainly been below 450mV, indicating a lean air/fuel mixture, the short term fuel trim count will be greater than 128. If the oxygen sensor voltage stays mainly above the threshold, the short term fuel trim count will be less than 128. A short term fuel trim count of 128 in Closed Loop indicates that no correction of the air/fuel mixture ratio is necessary. The short term fuel trim count is always 128 in Open Loop.

Long Term FT - Range -100% to 100% The Long Term Fuel Trim (FT) is derived from the short term fuel trim value and is used for the long term correction of the fuel delivery. A value of 0% indicates that the fuel delivery requires no compensation in order to maintain a 14.7:1 air/fuel ratio. A value below 0% means that the fuel system is too rich and the fuel delivery is being reduced. A value above 0% indicates that a lean condition exists and the PCM is compensating.

Long Term FT - Range: -0 to 255 The Long Term Fuel Trim (FT) is derived from the short term fuel trim value and is used for the long term correction of the fuel delivery. A long term fuel trim count of 128 indicates that the fuel delivery requires no compensation in order to maintain a 14.7:1 air/fuel ratio. A long term fuel trim count below 128 means that the fuel system is too rich and the PCM is decreasing fuel delivery. A long term fuel trim count above 128 indicates that a lean condition exists and the PCM is increasing fuel delivery.

Battery Voltage: This parameter specifies the battery positive voltage which was input from the Main Relay to the PCM.

MAP - Range: 0 - 125 kPa/0 - 5.10V The Manifold Absolute Pressure (MAP) sensor measures the change in the intake manifold pressure. This change in the pressure, which results from engine load and RPM changes, is converted into a voltage reading which is monitored by the Powertrain Control Module (PCM). A low voltage reading at the PCM indicates a low manifold pressure, and a high voltage reading at the PCM indicates a high manifold pressure.


BARO - Range: 0 - 125 kPa The Barometric Pressure (BARO) Sensor measures changes in atmospheric pressure. This parameter will read approximately 95 to 105 kPa at sea level.

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

TP Angle - Range: 0° - 90° The throttle angle parameter displays the throttle position in degrees. The Scan tool will display the numbers from 7 to 13 when the throttle valve is fully closed, and will display at 80 or close to 80 when the throttle valve is fully opened.

TP Sensor - Range: 0 - 5 volts The throttle position sensor reading provides the throttle valve opening information in the form of volts.

HO2S 1 - Range: 0 - 1275 mV The Heated Oxygen Sensor (HO2S) is the primary input to the fuel delivery system. The Powertrain Control Module (PCM) monitors the (HO2S) voltage when the system is in a Closed Loop operation. When the voltage reading is high, the air/fuel mixture is rich, and when the voltage reading is low, the air/fuel mixture is lean. Under normal operating conditions, the voltage reading should constantly fluctuate.

HO2S 2 - Range: 0 - 1275 mV The Rear Heated Oxygen Sensor (HO2S 2) represents the exhaust oxygen output voltage beyond the catalytic converter. This voltage will remain inactive or appear lazy within a range of 1 00mV (lean exhaust) and 900mV (rich exhaust) when the system is operating in a Closed Loop operation.

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

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

Loop Status - Range: Scan tool displays a Closed Loop or an Open Loop The scan tool displays a Closed Loop when the system enters a closed loop operation. This indicates that the Heated Oxygen Sensor (HO2S) sensor 1 is hot enough for the Powertrain Control Module (PCM) to control the fuel delivery. When the scan tool displays an Open Loop, the system is in an open loop operation. This indicates that the HO2S sensor 1 is cold and the PCM bases the fuel delivery on the throttle position and the MAP.

Engine Load - Range: 0% - 100% The Engine Load indicates that the engine load is based on the manifold absolute pressure. The higher the percentage, the more load the engine is under.

Total Fuel Trim: The value of Total Fuel Trim is obtained by putting the 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 at the stoichiometrical ratio of 14.7:1.

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

EVAP Duty Cycle - Range: 0% - 10% The EVAP Duty Cycle specifies the EVAP Canister Purge valve ON (valve open) time rate within a certain set cycle (PWM). Zero percent means that the purge valve is completely closed while 100% is a fully open valve.

EVAP Density Trim - Range: 0 to 100 This parameter indicates EVAP system purge concentration and is indicated in counts.

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

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

EGR Bypass Solenoid: This parameter indicates when the PCM is turning ON the EGR By-Pass Solenoid

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

Electrical Load Signal: The scan tool will display an On signal whenever certain electrical loads are indicated to the PCM. This will allow the PCM to adjust the engine idle to maintain acceptable engine performance.

Engine Coolant Fan: The scan tool will display an On signal whenever the PCM is turning the cooling fan relay ON.

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 PCM to adjust the engine idle to maintain acceptable engine performance.

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.

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

Spark - Range: -1° to 60° This displays the Powertrain Control Module (PCM) controlled value that is being used in order 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.

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

Fuel Tank Pressure Control Solenoid: The EVAP Tank Pressure Control Solenoid Vacuum Valve is Open when it is turned ON by the PCM and Closed when it is turned OFF. The scan tool will display On or Off to indicate whether the valve is being opened or closed.

Fuel Tank Pressure - Range: -33.5 - 33.5 In. H2O 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 Level - Range: 0% - 70% This parameter indicates the approximate fuel level in the fuel tank. The indicated fuel level may be only 70% even when the fuel tank is full.

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