Engine

A list of explanations for each data message displayed on the Tech 1 scan tool begins below.
This information will assist in tracking down emission or driveability problems, since the displays can be viewed while the vehicle is being driven. Refer to the "On-Board Diagnostic System Check" for additional information.

ENGINE SPEED RANGE 0 to 9999 RPM - Engine speed is computed by the PCM from the fuel control reference input (low resolution crankshaft position sensor). It should remain close to desired idle under various engine loads with engine idling.

MPH / KM/H - Range 0 to 255 km/h, 0 to 159 mph - The vehicle speed sensor signal is converted into km/h and mph for display.

ENGINE COOLANT LEVEL - Tech 1 Displays "Low" or "OK" - Shows the low or sufficient coolant level status in the coolant surge tank.

INT AIR TEMP SENSOR - The Intake Air Temperature (IAT) sensor is used by the PCM to adjust fuel delivery and spark timing according to incoming air density. The PCM supplies 5 volts to the IAT thermistor. As intake air temperature varies, the resistance changes causing a change in voltage drop across the sensor. The PCM measures the voltage drop across the sensor, and calculates the air temperature at the air intake.

MAP RANGE 11-105 kPa, 0.00 to 5.10 volts - The Manifold Absolute Pressure (MAP) sensor is attached to the intake manifold and measures changes in intake manifold pressure which result from engine speed and load changes. The PCM uses this information to adjust fuel delivery and spark timing.

BARO - The MAP sensor is also used to measure barometric pressure during ignition key "ON" cycle and during Wide Open Throttle (WOT), allowing the PCM to make fuel delivery and spark timing adjustments for changing altitudes.

RAW THROT POSITION - Range -13.9° to 93.4° This parameter shows actual throttle position (shifted). The closed throttle reading may change slightly due to choking of the throttle plate.

THROTTLE ANGLE - Degrees - Computed by the PCM from TP sensor voltage (throt position); should read 0% at idle, 100% at Wide Open Throttle (WOT).

THROTTLE POSITION SWITCH - Tech 1 Displays "Open" or "Closed" - The Throttle Position (TP) switch is part of the Idle Speed Control (ISC) motor. It sends an "Open" or "Closed" TP switch signal to the PCM.

THROT POSITION - Range 0 to 5.10 Volts - Used by the PCM to determine the amount of throttle demanded by the driver. Should read 0.20 to 0.74 volt at idle to above 4 volts at wide open throttle.

BANK 1 HO2S - Range 0 to 1132 mV - Represents the heated oxygen sensor output voltage. Should fluctuate constantly with a range between 100 mV (lean exhaust) and 1000 mV (rich exhaust) when operating in "Closed Loop."

BANK 2 HO2S - Range 0 to 1132 mV - Represents the HO2S 2 (catalyst monitor) output voltage. Should fluctuate much more slowly than the HO2S 1 signal when operating in "Closed Loop."

BANK 1 HO2S CROSS COUNTS - Range 0 to 255 - The number of times the oxygen sensor voltage crosses over the rich/lean threshold during a one second interval.

BANK 2 HO2S CROSS COUNTS - Range 0 to 255 - The number of times the oxygen sensor voltage crosses over the rich/lean threshold during a one second interval.

BANK 1 RICH/LEAN STATUS - Tech 1 Displays RICH or LEAN - Indicates whether exhaust 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.

BANK 2 RICH/LEAN STATUS - Tech 1 Displays RICH or LEAN - Indicates whether exhaust 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.

BANK 1 SHORT TERM FUEL TRIM - This 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, short term 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. Under certain conditions such as extended idle and high ambient temperatures, EVAP canister purge may cause short term fuel trim to read less than 100 counts.

BANK 1 LONG TERM FUEL TRIM - Long term fuel trim is derived from the short term 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 HO2S signal condition exists and the PCM is compensating by adding fuel (increased injector pulse width). Long term fuel trim tends to follow short term fuel trim; normal values of 110 to 150 counts at idle should not be considered unusual.

BANK 2 SHORT TERM FUEL TRIM - This 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, short term 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. Under conditions such as extended idle and high ambient temperatures, EVAP canister purge may cause short term fuel trim to read less than 100 counts.

BANK 2 LONG TERM FUEL TRIM - Long term fuel trim is derived from the short term 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 HO2S signal condition exists and the PCM is compensating by adding fuel (increased injector pulse width). Long term fuel trim tends to follow short term fuel trim; normal values of 110 to 150 counts at idle should not be considered unusual.

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 MAP 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 a 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.

FUEL TRIM CELL - Range 0 to 255 - Fuel trim cell is dependent upon engine speed and manifold absolute pressure readings. A plot of RPM vs. MAP is broken into 25 cells. Fuel trim cell indicates which cell is currently active. Cell twenty-five is the idle mode cell.

INJECTOR PULSE WIDTH (BANK 1 OR BANK 2) - Indicates the on time of the injectors in milliseconds. When engine load is increased, injector pulse width will increase.

CAMSHAFT POSITION COUNTER - Tech 1 Displays a Range of 0 to 255 Counts - This parameter is the number of cam signal inputs to the PCM. The counter will reset after 255 counts are reached.

IGNITION CONTROL (IC) SPARK MODE - Tech 1 Displays "PCM", or "ICM" - In PCM MODE, the PCM controls the ignition timing. The PCM calculates the desired ignition timing based on information it receives from the input sensors. In IGNITION CONTROL MODULE (ICM) mode, the ignition system operates independently from the PCM. The ignition control module maintains a base ignition timing of 10 degrees BTDC and is able to change this ignition timing slightly with increased engine speed. Ignition control mode is in effect whenever an IGNITION CONTROL fault is detected while the engine is running and it will have a noticeable effect on driveability.

SPARK-ADVANCE - Range -90° to 90° - 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.

IGNITION REFERENCE LOW - Tech 1 Displays "Volts" - Ignition ground voltage. Display shows the voltage difference between CKT 453 (ignition ground) and PCM ground shifted 2.5 volts. A reading of 2.500 volts means the ignition and PCM grounds are at the same voltage. A reading of 1.000 volt means the ignition ground voltage is 1.5 volts lower than the PCM ground and a reading of 3.500 volts means the ignition ground voltage is 1.0 volts above the PCM ground. Display shows ignition ground voltage level from 0.003 to 4.970 volts.

KNOCK SENSOR RETARD - Range 0° to -45° - Indicates the amount of spark advance in degrees that the PCM is removing from the Ignition Control (IC) in response to the Knock Sensor (KS) signal. Should read 0° at idle.

KNOCK SENSOR COUNTER - 0 to 255 Cnts - Display shows the number of instances of engine detonation detected by the knock sensor in one-eighth of a second from 0 to 255.

DESIRED EGR POS - Range 0 to 100% - The EGR pintle position which is being commanded by the PCM; should be very close to "ACTUAL EGR POS."

ACTUAL EGR POS - Range 0 to 100% - Represents the linear EGR pintle position signal in percent of travel 0% displayed indicates a closed EGR valve (EGR flow not allowed).

EGR PINTLE POS - The EGR valve contains a potentiometer type position sensor that provides a voltage proportional to pintle position. Pintle position is used by the PCM for "Closed Loop" control of valve pintle position to follow commanded position for diagnostics, and to correct fuel and spark for EGR.

SYSTEM VOLTAGE - Range 0.0 to 25.5 Volts - This represents the system voltage measured by the PCM at its ignition #1 feed.

FUEL PUMP (FP) MONITOR - Range 0 to 25.5 Volts - Provides information to the PCM about the fuel pump power supply condition of CKT 120 GRY through the fuel pump relay or the oil pressure switch/sensor.

FUEL PUMP RELAY - When the ignition switch is turned to the "ON" position, the PCM turns the fuel pump relay "ON" for two seconds. If the PCM does not receive ignition reference pulses within two seconds, the PCM will shut "OFF" the fuel pump.

MALFUNCTION INDICATOR LAMP (MIL) STATUS - Tech 1 Displays "ON" or "OFF" - The MIL (Service Engine Soon) is controlled by the PCM through CKT 419 and is used to indicate that the PCM has detected a problem that affects vehicle emissions, driveability and could cause powertrain damage.

FUEL EVAP ENABLE - Tech 1 displays "OFF" or "ON"- This is the PCM Control status of the fuel evaporative solenoid. While monitoring the vehicle load and driving conditions, the PCM will cycle the fuel evaporative solenoid "ON" or "OFF."

FUEL EVAP PURGE - Range 0 to 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.

FAN CONTROL (FC) RELAY #1, 2, 3 - When the PCM is commanding the fan 1 or 2 "ON," the Tech 1 display will switch from "OFF" to "ON."

QDM 1,2, 3 - Tech 1 Displays "OK" or "FAULT" - Each internally in the PCM located QDM controls four (4) independent ground circuits for PCM activated components. The quad-driver modules have PCM -monitored fault lines, which will set a fault code, if the QDM fault detect circuit senses a voltage other than the accepted values.

QDM 4, 5 - Tech 1 Displays "OK" or "FAULT" - Each internally in the PCM located QDM controls four (4) independent ground circuits for PCM activated components. The quad-driver modules have PCM monitored fault lines, which will set a fault code, if the QDM fault detect circuit senses a voltage other than the accepted values.

INJECTOR STATUS - Tech 1 Displays "OK" or "FAULT" - The Tech 1 will display "FAULT" if the PCM has detected an improper voltage level in any of the fuel injector circuits to determine if any of the eight (8) injectors are misfiring.

DESIRED TORQUE LEVEL - Range 0 to 100% - The EBTC sends a "Desired Torque Level" signal request to the PCM to decrease torque output from the powertrain to reduce wheel slip during acceleration for traction control.

PASS-KEY STARTER INHIBIT - Tech 1 Displays "OK/Inhibited" - The starter inhibit circuit is an output from the PCM and an input to the PASS-Key II decoder module. When the PCM detects an engine running condition, it will send a signal to the PASSKey module to prevent cranking during engine running condition.

IGNITION CYCLE COUNTER - Range 0 to 50 Counts - Display shows counts. The count increases by 1 with each "ON" to "OFF" cycle. When a trouble code sets, the counter is set to 0. If the trouble code becomes history the counter will increment with each key cycle until another code is set, or until the key has been cycled at which time the code will be erased.

INTAKE AIR TEMP - Range -40° to 199°C, -40° to 389°F - The PCM converts the resistance of the Intake Air Temperature (IAT) sensor to degrees. Intake air temperature is used by the PCM to adjust fuel delivery and spark timing according to incoming air density.

TRANS FLUID TEMP - Range -40° to 151°C, -40° to 304°F - The PCM converts the resistance of the transaxle temperature sensor to degrees. Trans temp is used to determine "Hot Mode" TCC operation.













ENGINE SPEED - Range 0 to 9999 RPM - Engine speed is computed by the PCM from the fuel control reference input (low resolution crankshaft position sensor). It should remain close to desired idle under various engine loads with engine idling.

DESIRED IDLE - Range 0 to 2040 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.

ENGINE COOLANT TEMP - Range -40°C to 199°C, -40°F to 389°F - The Engine Coolant Temperature (ECT) sensor is mounted in the cylinder head and sends engine coolant 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 high), 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.

MAP - Range 11-105 kpa, 0.00 to 5.10 Volts The Manifold Absolute Pressure (MAP) sensor is attached to the intake manifold and measures changes in intake manifold pressure which result from engine speed and loud changes. The PCM uses this information to adjust fuel delivery and spark timing.

THROT POSITION - Range 0 to 5.10 Volts - Used by the PCM to determine the amount of throttle demanded by the driver. Should read .20 to .74 volt at idle to above 4 volts at wide open throttle.

THROT ANGLE - Degrees - Computed by the PCM from TP (throt position) sensor voltage: should read 0% at idle, 100% at Wide Open Throttle (WOT).

THROTTLE POSITION SWITCH - Tech 1 Displays "Open" or "Closed" - The Throttle Position (TP) switch is part of the Idle Speed Control (ISC) motor. It sends an "OPEN" or "CLOSED" TP switch signal to the PCM.

POWER STEERING PRESSURE (PSP) SWITCH - Tech 1 States Normal or High Pressure - PCM compensates engine idle depending on steering load conditions. Tech 1 will display "HIGH PRESSURE" due to increase of power steering fluid pressure, while turning steering wheel. Tech 1 displays "NORMAL" under no load condition.

SHIFT MODE SWITCH - Tech 1 Displays Normal/Performance - This parameter is the actual state of the performance mode control program (within the PCM). The Tech 1 will display "PERFORMANCE" when the performance mode is active (Performance Shift Calibration). The Tech 1 will display "NORMAL" when the performance mode is not active (Normal Shift Calibration).

A/C CLUTCH RELAY - 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.

SYSTEM VOLTAGE - Range 0 to 25.5 Volts - This represents the system voltage measured by the PCM.

A/C LOW SIDE TEMP. - Range -40°C to 85°C, -40°F to 215°F - The PCM monitors the A/C low pressure vapor refrigerant line of the evaporator circuit based on the pressure - temperature relationship of freon the A/C low pressure will be determined by the PCM to control the cooling fan operation, A/C compressor, clutch and A/C DTCs.

A/C HI SIDE TEMP. - Range -13°C to 215°C, 9°F to 455°F - Monitors the A/C high pressure liquid refrigerant line of the condenser circuit. Based on the pressure - temperature relationship of freon the A/C high pressure will be determined. Range 1379 kPa (200 psi) - 2960 kPa (430 psi).

A/C HIGH PRESSURE SWITCH - Tech 1 Displays "Normal" or "High Pressure" - The switch is normally closed. If the A/C pressure rises too high, the switch contacts opens, interrupting the voltage signal to the PCM. The PCM de-energizes the A/C compressor control relay and the compressor stops running to prevent A/C system damage.

A/C REQUEST - Tech 1 Displays "YES" or "NO" - Represents the state of the A/C request input from the A/C selection switch control assembly.

PASS-Key II FUEL - An input from the PASS-Key II 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 will switch to "INHIBITED" and the fuel system may be disabled.

GEN "L" TERMINAL - Displays "OFF" or "ON" - PCM monitors CKT 225 that the PCM is supplying with 12 volts to the generator internally located voltage regulator at terminal "L" to initiate the generator charging mode and to enable the generator self energizing operation after the engine is running.

GEN "L" TERMINAL STATUS - Displays "OK" or "NO OUTPUT" - Detects generator "L" terminal circuit problem when generator regulator ground out and changes CKT 225 value in the PCM to low due to problems in the charging system.

TP SENSOR LEARN ATTEMPTS- Displays Counts 0 to 255. The PCM monitors the TP sensor and the ISC throttle position switch during the TP sensor learning routine, when the ignition is "OFF." Calculating the factors the PCM corrects the TP sensor position to the "learned" value.

TP SENSOR LEARN COMPLETE - Displays Counts 0 to 255 - Displays on internal PCM parameter. Each time the vehicle is driven the TP sensor system learns how many counts are required to produce a given desired idle.

C/C BRAKE SWITCH - Tech 1 Displays "APPLIED" or "RELEASED" - When the brake pedal is applied, the brake switch sends a signal to the PCM to disengage cruise control.

C/C ON/OFF SW. - Tech 1 Displays "ON" or "OFF" - When the C/C ON/OFF switch is "ON" Tech 1 should display "ON." When the C/C ON/OFF switch is "OFF" Tech 1 should display "OFF."

C/C RES/ACCEL SW. - Tech 1 Displays "ON" or "OFF" - When the RES/ACCEL switch is held in the RES/ACCEL position, the Tech 1 will display "ON." When the switch is released, the Tech 1 should display "OFF."

C/C SET/CST SW. - Tech 1 Displays "ON" or "OFF" - These parameters are 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.

CRUISE MODE - There are seven different modes which cruise control may be operating in. They are: "OFF," "DISABLED," "STAND-BY," "CRUISE," "RESUME," "ACCEL" and "COAST."

C/C SET SPEED - Range 0 to 255 MPH - The speed that the cruise control system is trying to maintain.

C/C VACUUM SOL. - Tech 1 Displays "ON" or "OFF" - The cruise control vac and vent solenoid are PCM controlled outputs that control the amount of vacuum applied to the servo. The throttle position will increase when the vacuum solenoid and the vent solenoid are "ON." The throttle position will decrease when the vac solenoid and the vent solenoid are "OFF."

C/C VENT SOL. - Tech 1 Displays "ON" or "OFF" - The cruise control vac and vent solenoid are PCM controlled outputs that control the amount of vacuum applied to the servo. The throttle position will increase when the vacuum solenoid and the vent solenoid are "ON." The throttle position will decrease when the vac solenoid and the vent solenoid are "OFF."

ACT. SERVO POSITION - Range 0 to 100% - The actual position of the Servo Position Sensor (SPS) given in percent.

DES. SERVO POSITION - Range 0 to 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. When engine load is increased, injector pulse width will increase.

C/C LASH LERN - Range Counts - Used by the PCM to calculate the number of pulses between the C/C servo activation and the throttle movement to compensate for servo linkage misalignment by adding to the normal number of pulses needed to reach a desired speed.

C/C OUT MPH RANGE - Tech 1 displays "YES" or "NO" - This parameter will change from "NO" to "YES" if there is a 20 MPH greater vehicle speed than the set speed.

C/C OUT RPM RANGE - Tech 1 displays "YES" or "NO" - This parameter will change from "NO" to "YES" if engine RPM exceeds 6350 RPM with cruise engaged.

C/C OVER ACCEL. - Tech 1 displays "NO" or "Over Accel" - This parameter will change from "NO" to "Over Accel" if the vehicle accelerates 16 mph in one second.

CHANGE IN SPEED - Tech 1 displays "YES" or "NO" - This parameter will change from "NO" to "YES" if a new set speed is selected and will remain "YES" for that ignition cycle.

TORQUE DELIVERED - Tech 1 displays 0 to 510 lbs. ft. - This parameter is the amount of torque that is delivered from the engine. (Input torque to the transaxle.)

TRANSAXLE OIL LIFE - Range 0 to 100% - Represents the transaxle oil life index that is calculated and maintained by the PCM.

ENGINE OIL LIFE - Range 0 to 100% - Represents the engine oil life index that is calculated and maintained by the PCM.

TCC BRAKE SWITCH - Scan Tool Displays APPLIED/RELEASED - This parameter indicates the state of the TCC brake switch circuit input. "APPLIED" indicates a 0 voltage input (brake switch open, brake pedal applied). "RELEASED" indicates a B + voltage input (brake switch closed, brake pedal released).

TCC ENGAGED - Display "YES" or "NO" - This parameter is the commanded state of the TCC solenoid. "YES" indicates a commanded energized state (current flowing through the solenoid). "NO" indicates a commanded non-energized state (current not flowing through the solenoid).

PARK/NEUTRAL POSITION - P-N displayed indicates the gear select lever is in "PARK" or "NEUTRAL." RDL displayed indicates the gear select lever is in "REVERSE," "DRIVE" or "LOW RANGE."

TRANS RANGE SWITCH (5W) - Scan Tool Displays a Range of Invalid, Park/Neutral, Reverse, Drive 4, Drive 3, Drive 2, and Low - This parameter is the decoded status of the three A/B/C range inputs from the transaxle range pressure switch assembly and represents the position of the transaxle manual valve.

EXTENDED TRAVEL BRAKE - Tech 1 Displays "APPLIED/RELEASED" - The extended travel brake switch contacts of the torque management brake switch. The Tech 1 will display "APPLIED" with the brake pedal depressed and "RELEASED" with the brake pedal released.

TCM CAL ID Calibration - Display shows a three digit code that uniquely identifies the program stored in the PROM for control calibration. The displayed number is not the service part number.

LO OCTANE IND. - Tech 1 displays "NO" or "ACTIVE." This display is calculated by the PCM based on the status of the knock sensor test. If the PCM determines that detonation is occurring during a spark knock test, the display will change from "NO" to "ACTIVE." "ACTIVE" means the PCM is making corrections to the spark curve based on the knock signal.