Engine Data Display Table Definitions
ENGINE DATA DISPLAY TABLE DEFINITIONSPCM/ECM Data Description
The following information will assist in diagnosing emission or driveability problems. A first technician can view the displays while the vehicle is being driven by second technician. Refer to Powertrain On-Board Diagnostic (OBD II) System Check for additional information. See Non-Trouble Code Diagnostic Procedures.
A/C Clutch
The A/C Relay represents the commanded state of the A/C clutch control relay. The A/C clutch should be engaged when the scan tool displays ON.
A/C Pressure
The A/C High Side displays the pressure value of the A/C refrigerant pressure sensor. The A/C High Side helps to diagnose the diagnostic trouble code (DTC) P0533.
A/C Request
The A/C Request represents whether the air conditioning is being requested from the HVAC selector. The input is received by the instrument panel cluster and then sent over universal asynchronous receiver transmitter (UART) serial data to the powertrain control module (PCM)/engine control module (ECM) and finally to the scan tool over class 2 serial data.
Air Fuel Ratio
The Air Fuel Ration indicates the air to fuel ratio based on the Oxygen Sensor (O2S 1) inputs. The PCM/ECM uses the fuel trims to adjust fueling in order to attempt to maintain an air fuel ratio of 14.7:1.
BARO
The Barometric Pressure (BARO) sensor measures the change in the intake manifold pressure which results from altitude changes. This value is updated at ignition ON and also at Wide Open Throttle (WOT).
BPW Bank 1
Indicates the base Pulse Width Modulation (PWM) or ON time of the indicated cylinder injector in milliseconds. When the engine load is increased, the injector pulse width will increase.
Calculated Air Flow
The calculated airflow is a calculation based on manifold absolute pressure. The calculation is used in several diagnostics to determine when to run the diagnostics.
Calculated Load
Indicates engine load based on Manifold Absolute Pressure (MAP). The higher the percentage, the more load the engine is under.
Camshaft Activity Counter
The Camshaft Position (CMP) activity counter displays the activity sent to the PCM/ECM from the CMP sensor. The counter will continually increment while the engine is running. The CMP activity counter is helpful in diagnosing DTC P0342.
Desired Idle
The PCM/ECM commands the idle speed. The PCM/ECM compensates for various engine loads in order to maintain the desired idle speed. The actual engine speed should remain close to the desired idle under the various engine loads with the engine idling.
Engine Coolant Temperature
The Engine Coolant Temperature (ECT) sensor sends engine temperature information to the PCM/ECM. The PCM/ECM supplies 5 volts to the engine coolant temperature sensor circuit. The sensor is a thermistor which changes internal resistance as temperature changes. When the sensor is cold (internal resistance high), the PCM/ECM monitors a high voltage which it interprets as a cold engine. As the sensor warms (internal resistance decreases), the voltage signal will decrease and the PCM/ECM will interpret the lower voltage as a warm engine.
EGR Desired Position
The desired exhaust gas recirculation (EGR) position is the commanded EGR position. The PCM/ECM calculates the desired EGR position. The higher the percentage, the longer the PCM/ECM is commanding the EGR valve ON.
Engine Run Time
The engine run time is a measure of how long the engine has been running. When the engine stops running, the timer resets to zero.
Engine Speed
Engine Speed is computed by the PCM/ECM from the fuel control reference input. It should remain close to desired idle under the various engine loads with the engine idling.
EVAP Purge
The Evaporative (EVAP) Emission purge valve solenoid is a proportional signal used in order to control the EVAP canister purge function. At 0% the valve is commanded fully closed. 100% implies that the valve is fully open.
EVAP Purge Solenoid
When energized, the EVAP Emission Canister Purge Solenoid allows the fuel vapor to flow from the EVAP Canister to the engine. The EVAP Emission Canister Purge Solenoid is normally closed. The EVAP Emission Canister Purge Solenoid is pulse width modulated by the PCM/ECM. The EVAP Emission Canister Purge Solenoid reads 0% when closed and 100% when fully opened.
EVAP Vent Solenoid
The EVAP Emission Vent Solenoid allows fresh outside air to the EVAP Emission Canister during purge mode. The EVAP Emission Vent Solenoid allows the diagnostic to pull a vacuum on the fuel tank by closing the vent solenoid.
Fan
The Fan Control (FC) Relay is commanded by the PCM/ECM. The FC Relay displays the command as ON or OFF.
Fuel Level Sensor
The Fuel Level Sensor monitors the fuel level in the tank. The Fuel Level Sensor monitors the rate of change of the air pressure in the EVAP Emission Canister Purge System. Several of the Enhanced EVAP Emission Canister Purge System diagnostics are dependent upon the correct fuel level.
Fuel Tank Pressure Sensor
The fuel tank pressure sensor measures the difference between the pressure or the vacuum in the fuel tank and the outside air pressure. When the air pressure in the fuel tank equals the outside air pressure, the output voltage of the sensor is 1.3 to 1.7 volts.
IAC Position
The scan tool displays the PCM/ECM command for the Idle Air Control (IAC) pintle position in counts. The higher the number of counts, the greater the commanded idle speed reads. The Idle Air Control responds to changes in the engine load in order to maintain the desired idle rpm.
Intake Air Temperature
The PCM/ECM converts the resistance of the Intake Air Temperature (IAT) sensor to degrees in the same manner as the ECT sensor. Intake air temperature is used by the PCM/ECM to adjust fuel delivery and spark timing according to incoming air density.
Ignition 1 (Voltage)
The ignition volts represent the system voltage measured by the PCM/ECM at the ignition feed circuit.
Knock Retard
The Knock Sensor (KS) Retard indicates the amount of spark advance the PCM/ECM is decreasing in response to the KS signal.
Knock Present
The KS Noise Channel indicates when the PCM/ECM detects the KS signal. The PCM/ECM should display NO at idle.
Long Term FT
The Long Term Fuel Trim (FT) is derived from the short term fuel trim value. The Long Term FT is used for the long term correction of the fuel delivery. A value of 128 counts (0%) indicates that the fuel delivery requires no compensation in order to maintain a 14.7:1 air to fuel ratio. A value below 128 counts means that the fuel system is too rich and the fuel delivery is being reduced. The PCM/ECM is decreasing the injector pulse width. A value above 128 counts indicates that a lean condition exists for which the PCM/ECM is compensating.
Loop Status
The Closed Loop is displayed indicating that the PCM/ ECM is controlling the fuel delivery according to the Oxygen Sensor (O2S 1) voltage as close to an air/fuel ratio of 14.7 to 1 as possible.
MAP
The MAP sensor measures the change in the intake manifold pressure which results from engine load and speed changes. As the intake manifold pressure increases, the air density in the intake also increases and the additional fuel is required.
Misfire Current #1-4
Indicates the number of current misfires that are present in the indicated cylinder. Increments only when misfire is current.
Misfire History #1-4
Indicates the number of misfires that have occurred after 195 current misfires have been counted. The current misfire counter will add its misfires to the history misfire counter after 195 total misfires have taken place. If 1 cylinder is misfiring, the misfiring current counter will have 195 misfires counted before adding to its history counter. If 2 cylinders are misfiring, the misfiring current counter will add to their history counters after 97 misfires. The counter increments only after a misfire diagnostic trouble code (DTC) has been set.
Oxygen Sensor Bank 1 Sensor 1
The pre-converter Oxygen Sensor (O2S 1) reading represents the exhaust oxygen sensor output voltage. This voltage will fluctuate constantly between 100 mv (lean exhaust) and 900 mv (rich exhaust) when the system is operating in a Closed Loop.
Oxygen Sensor Bank 1 Sensor 2
The post-converter Heated Oxygen Sensor (HO2S 2) represents the exhaust oxygen output voltage past the catalytic converter. This voltage remains inactive, or the voltage will appear lazy within a range of 100 mv (lean exhaust) and 900 mv (rich exhaust) when operating in a Closed Loop.
Short Term FT
The Short Term FT represents a short term correction to fuel delivery by the PCM/ECM in response to the amount of time the oxygen sensor voltage spends above or below the 450 mv threshold. If the oxygen sensor has mainly been below 450 mv, indicating a lean air/fuel mixture, short term fuel trim will increase to tell the PCM/ECM to add fuel. If the oxygen sensor voltage stays mainly above the threshold, the PCM/ECM will reduce fuel delivery to compensate for the indicated rich condition.
Short Term FT Average
The Short Term FT Average is derived from the short term fuel trim from all of the cells. The PCM/ECM takes all of the values and then creates one average value.
Spark
This is a display of the spark advance Ignition Coil (IC) calculation which the PCM/ECM is programming in the ignition system. It computes the desired spark advance using data such as engine temperature, rpm, engine load, vehicle speed and operating mode.
TCC Brake Switch
When the brake pedal is applied, the Torque Converter Clutch (TCC) brake switch sends a signal to the PCM/ECM to disengage the TCC and disable the cruise control.
Total Misfire Current Counter
Indicates the total number of misfires that have been detected in all the cylinders after 100 engine cycles. One cycle equals one complete 4 stroke cycle. The total misfire only increments during the steady state cruise conditions.
TP Angle
From the Throttle Position (TP) Sensor voltage input, the PCM/ECM computes the TP. The TP Angle will auto zero to 0% at idle (TP voltage below 0.90 volts). The TP Angle will read 100% at WOT.
TP Sensor
The PCM/ECM uses the TP Sensor in order to determine the amount of the throttle demanded by the vehicle's operator. The TP Sensor reads between 0.36-0.96 volts at idle to above 4 volts at WOT.
Vehicle Speed
The vehicle speed sensor signal is converted into mph or kph for display. The vehicle speed output from the PCM/ECM is 4000 pulses per mile. The scan tool uses the class 2 serial data from the PCM/ECM to obtain vehicle speed, while the Instrument Panel Cluster (IPC), cruise control module and the chime alarm module use the 4000 rpm output.