Scan Tool Data Definitions
ENGINE SPEED - Range 0-9999RPM - Engine speed is computed by the PCM from the fuel control reference input. It should remain close to desired idle under various engine loads with engine idling.
DESIRED IDLE - Range 0-3175 RPM
The idle speed that is commanded by the PCM. The PCM will compensate for various engine loads to keep the engine at the desired idle speed.
ENG COOL TEMP - Range -40°C to 199°C, (-40°F to 389°F)
The Engine Coolant Temperature (ECT) Sensor is mounted in the intake manifold and sends engine temperature information to the PCM. The PCM 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 is high, and the PCM monitors a high signal voltage which it interprets as a cold engine. As the sensor warms internal resistance decreases, the voltage signal will decrease and the PCM will interpret the lower voltage as a warm engine.
INTAKE AIR TEMP - Range -40°C to 199°C (-40°F to 389°F)
The PCM converts the resistance of the intake air temperature sensor to degrees. Int Air Temp (lAT) is used by the PCM to adjust fuel delivery and spark timing according to incoming air density.
THROT POSITION - Range 0-5.10 Volts
Used by the PCM to determine the amount of throttle demanded by the driver. Should read 0.2 -0.74 volt at idle, to above 4 volts at wide open throttle.
THROTTLE ANGLE - Range 0-100%
Computed by the PCM from TP sensor voltage (Throt Position). Should read 0% at idle, 100% at wide open throttle.
MASS AIR FLOW - Range 0-255.9 Gm/Sec
The PCM processes the the mass air flow sensor input signal and calculates air flow rate in grams per second, indicating the amount of airflow entering the engine.
CALC. ENG. LOAD - Range 0-255 Counts
Engine load is calculated by the PCM by engine speed and mass airflow. Should increase with an increase in RPM or airflow.
HO2S - Range 0-1096 mV
Represents the exhaust oxygen sensor output voltage. Should fluctuate constantly within a range between 100 mV (lean exhaust) and 1000 mV (rich exhaust) when operating in "Closed Loop."
LOOP STATUS - Tech 1 Displays "OPEN LOOP" or "CLOSED LOOP"
"Closed Loop" displayed indicates that the PCM is controlling fuel delivery according to oxygen sensor voltage. In "Open Loop," the PCM ignores the oxygen sensor voltage and bases the amount of fuel to be delivered on TP sensor, engine coolant temperature, and MAF sensor inputs only. "Closed Loop" operation should begin when the oxygen sensor becomes active, engine coolant temperature exceeds 50°C (122°F) for more than 30 seconds and the PCM has seen an RPM of 1200 or greater for 10 seconds. At extremely high ambient temperatures or when towing a trailer, it is possible for the system to remain in "Open Loop" operation to control catalytic converter temperatures.
HO2S CROSS COUNTS - Range 0-255 Counts
The number of times the oxygen sensor voltage crosses over the rich/lean threshold during a one second interval.
RICH/LEAN STATUS - Tech 1 Displays "RICH" or "LEAN"
Indicates whether oxygen sensor voltage is above (rich) or below (lean) the 450 mV oxygen sensor threshold voltage. Should change constantly, indicating that the PCM is controlling the air/fuel mixture properly.
SPARK ADVANCE - Range -90° to 9O°
This is a display of the spark advance calculation which the PCM 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.
ST. FUEL TRIM - Range 0-180 Counts
S.T. fuel trim represents a short-term correction to fuel delivery by the PCM in response to the amount of time the oxygen sensor voltage spends above or below the 450 mV threshold. If the oxygen sensor voltage has mainly been below 450 mV, indicating a lean air/fuel mixture, S.T. fuel trim will increase to tell the PCM to add fuel. If the oxygen sensor voltage stays mainly above the threshold, the PCM will reduce fuel delivery to compensate for the indicated rich condition.
NOTE: Under certain conditions such as extended idle and high ambient temperatures, canister purge may cause S.T. fuel trim to read less than 100 counts.
L.T. FUEL TRIM - Range 0-160 Counts
L.T. FUEL TRIM is derived from the S.T. fuel trim value and is used for long-term correction of fuel delivery. A value of 128 counts 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 PCM is compensating by adding fuel (increased injector pulse width).
NOTE: L.T.Fuel Trim tends to follow S.T. Fuel Trim; a value of less than 100 counts due to canister purge at idle should not be considered unusual.
FUEL TRIM CELL - Range 0-15
Fuel trim cell is dependent upon engine speed and mass air flow readings. A plot of RPM vs. MAF is broken into 16 cells. FUEL TRIM CELL indicates which cell is currently active.
KNOCK RETARD - Range 0° -90°
Indicates the amount of spark advance the PCM is removing from ignition control in response to the knock sensor signal. Should read O° at idle.
KNOCK SIGNAL - Tech 1 Displays "YES" or "NO"
Indicates whether or not a knock signal is being detected by the PCM. Should read "NO" at idle.
IDLE AIR CONTROL - Range 0-255 Counts
Displays the commanded position of the idle air control pintle in counts. The higher the number of counts, the greater the commanded idle speed. Idle air control should respond fairly quickly to changes in engine load to maintain desired idle rpm.
PARK/NEUTRAL POS - Tech 1 Displays "P-N" or "-RDL"
"P-N" displayed indicates that the gear select lever is in park or neutral.
MPH Km/h - Range 0-155 mph (0-255 km/h)
The vehicle speed sensor signal is converted into mph and km/h for display.
TCC MODE - The modes are: "OFF, "RELEASE," "APPLY," and "ON."
The "APPLY" mode will be active for approximately 1 to 5 seconds.
TCC DUTY CYCLE - Range 0-100%
This is the relative position of the PWM solenoid that controls TCC apply pressure; 100% is low pressure, 0% is high pressure.
TCC SLIP - Range 0-255 RPM
The amount of slip between engine speed and transmission speed. When TCC MODE is "ON" there should only be a small amount of slip.
N/V RATIO - Range 0-255
Represents the ratio obtained by dividing engine speed by vehicle speed. Should stay constant in 3rd or 4th gear with the TCC locked.
CURRENT WEAK CYL - Tech I Displays Cylinder Number or "NONE"
The PCM monitors RPM and crank position, and when an apparent misfire is detected for more than 25 consecutive crankshaft revolutions the weak cylinder number is displayed.
DRIVER SELECT SW. (VIN 1 ONLY)
Indicates the position of the driver select switch. In the "sporty" position, the PCM alters shift points to give a firmer shift.
BOOST DUTY CYCLE - Range 0-100% (VIN-1 only)
Represents the amount of boost commanded by the PCM. Full boost is commanded when 100% is displayed.
CAM/CRANK ERROR - Tech 1 Range 0-255 Counts
Represents the number of times an incorrect ratio of fuel control pulses to cam signal pulses have been seen by the PCM. The PCM will normally count 0-2 errors during startup.
TRANS FLUID TEMP - Range -40°C to 199°C (-40°F to 389°F)
The PCM converts the resistance of the transaxle fluid temperature sensor to degrees. Trans fluid temp is used to determine "HOT MODE" TCC control and for traction control operation.
FUEL EVAP PURGE - Range 0-100%
A proportional signal used to control evap canister purge function; 0% implies the valve is commanded fully closed while 100% implies that the valve is fully open.
SYSTEM VOLTAGE - Range 0-25.5 Volts
This represents the system voltage measured by the PCM at its ignition feed (CKT 439).
A/C REQUEST - TECH 1 Displays "YES" or "NO"
Represents the state of the A/C request input from the control head.
A/C CLUTCH - Tech 1 Displays "ON" or "OFF"
Represents the commanded state of the A/C clutch control relay. Clutch should be engaged when "ON" is displayed.
A/C HEAD PRESS - Tech 1 Displays "OK" or "HIGH"
Represents the state of the A/C head pressure switch. When the A/C refrigerant pressure rises above 1448 kPa (210 psi) the switch should close, informing the PCM to turn "ON" the high speed coolant fans.
ACTUAL EGR POS - Tech 1 Range 0-100%
Represents the actual position of the EGR Pintle in percent. 0% displayed indicates a fully extended pintle (EGR flow not allowed).
DESIRED EGR POS. - Tech 1 Range 0-100%
Represents the EGR pintle position that the PCM is commanding; should stay fairly close to "ACTUAL EGR POS."
EGR PINTLE POS - Tech 1 Range 0-5.10 Volts
The actual voltage of the Pintle Position Sensor PCM input. A low voltage indicates a fully extended pintle (closed valve); A voltage near 5 volts indicates a retracted pintle (open valve).
TCC BRAKE SWITCH - Tech I Displays "APPLIED" or "RELEASED"
When the brake pedal is applied, the switch sends a signal to the PCM to disengage the TCC. Shoud display "APPLIED" with brake pedal depressed.
C/C SET SPEED - Range 0-255 mph
The speed that the cruise control system is trying to maintain.
DESIRED SERVO POS. - Range 0-100%
A value given in percent calculated from the cruise set speed. It is the reference point for the PCM as to where the Servo Position Sensor (SPS) should be at a given speed.
ACTUAL SERVO POS. - Range 0-100%
The actual position of the Servo Position Sensor (SPS) given in percent. Should stay close to desired Servo Pos. up to full servo stroke (50% - 100% desired Servo Pos.)
CRUISE MODE
There are seven different modes which cruise control may be operating in. They are: "OFF," "DISENGAGED," "STAND-BY," "CRUISE," "RESUME," "ACCEL" and "COAST."
RAW SERVO POS. - Range 0-255 Counts
When the servo is at rest, the Tech 1 should display a value of 15 to 85 counts and be holding steady. The PCM converts this value to a percent for "ACTUAL SERVO POSITION."
C/C ON/OFF SW
Tech 1 Displays "ON" or "OFF"
C/C RES/ACCEL SW
Tech 1 Displays "ON" or "OFF"
C/C SET/COAST 5W - Tech 1 Displays "ON" or "OFF"
These parameters represent the Cruise Control (C/C) switches. The Tech 1 may be used to determine if the cruise control switches are functioning properly. When the "ON"/"OFF" switch is "ON" and the brake is not depressed, the display on the Tech 1 will switch from "OFF" to "ON" as the corresponding switch is pushed.
C/C VACUUM SOL
Tech 1 Displays "ON" or "OFF"
C/C VENT SOL - Tech 1 Displays "ON" or "OFF"
The cruise control vacuum and vent solenoids are PCM controlled outputs that control the amount of vacuum applied to the servo. The throttle position will increase when the vacuum solenoid is "ON" and the vent solenoid is "ON." The throttle position will decrease when the vacuum solenoid is "OFF" and the vent solenoid is "OFF."
SHIFT A SOL
Tech 1 Displays "ON" or "OFF"
SHIFT B SOL - Tech 1 Displays "ON" or "OFF"
The PCM commanded state of each shift solenoid is displayed. In park or neutral, both solenoids should be "ON."
PRNDL P, A, B, C - Tech 1 Displays "HIGH" or "LOW"
A transmission range switch is used as an input to let the PCM know what position the gear select lever is in. Tech 1 status will switch from "HIGH" to "LOW" as different combinations are met. In "PARK," PRNDL "P" and "A" will be "LOW"; "B" and "C" will be "HIGH."
C/C BRAKE SWITCH - Tech I Displays "APPLIED" or "RELEASED"
When the brake pedal is applied, the brake switch sends a signal to the PCM to disengage cruise control.
TRANS RANGE SWITCH
The Tech 1 displays the decoded position of the transmission range switch inputs. If a valid combination is not seen by the PCM, "DRIVE 4" will be displayed.
COMMANDED GEAR
The gear that the PCM is commanding the 4T60E transaxle to be in. In "PARK," the Tech 1 will display "First."
P/N - Tech 1 Displays "YES" or "NO"
"YES" displayed indicates that the gear select lever is in park or neutral.
2nd, 3rd, 4th ACTUAL - Tech 1 Displays "YES" or "NO"
The PCM looks at "PRNDL SWITCH" position and "COMMANDED GEAR." The actual forward gear that the transaxle is in will be the lower of the two because the manual valve can override the PCM commanded gear.
FAN 1
When the PCM is commanding the low speed or puller fan(s) "ON," the Tech 1 display will switch from "OFF" to "ON."
FAN 2
When the PCM is commanding the high speed or puller fan(s) "ON," the Tech 1 display will switch from "OFF" to "ON."
QOM 1,2,4 - Tech 1 Displays "HIGH" or "LOW"
Quad- driver modules are used to turn "ON" various devices. The Tech 1 display will switch from "LOW" to "HIGH" if there is a circuit problem.
PASSKEY FUEL - Tech 1 Displays "ENABLED" or "DISABLED"
An input from the Theft Deterrent module that tells the PCM to enable the injectors if the proper signal is received. The Tech 1 will normally display "ENABLED." If the PASS-Key II test has failed, the display may switch to "DISABLED," in which case the fuel system will be disabled.
CALIBRATION ID - Range O-9999
The calibration identification describes the particular PROM being used in the PCM. The displayed number is not the service part number.
TIME FROM START - Range 0:00:00-18:12:15 HR/MIN/SEC
A measure of how long the engine has been running. When the engine stops, it is reset to zero.