Engine Tech 2 Data Definitions and Ranges

A/C CLUTCH - Tech 2 Displays ON or OFF -
Indicates whether the PCM has commanded the A/C clutch ON. Used in A/C system diagnostic.

A/C REQUEST - Tech 2 Displays YES or NO -
Indicates the state of the A/C request input circuit from the HVAC controls. The PCM uses the A/C request signal to determine whether A/C compressor operation is being requested.

AIR/FUEL RATIO - Tech 2 Range 0.0-25.5 -
Air/fuel ratio indicates the PCM commanded value. In closed loop, the air/fuel ratio should normally be displayed around "14.2-14.7". A lower air/fuel ratio indicates a richer commanded mixture, which may be seen during power enrichment or TWC protection modes. A higher air/fuel ratio indicates a leaner commanded mixture. This can be seen during deceleration fuel mode.

AP1 -Tech 2 Range 0%-100% -
AP (accelerator pedal) angle is computed by the PCM from the AP sensor voltage. AP angle should display "13%" at idle and "85-89%" at wide open throttle.

AP2 -Tech 2 Range 0%-100% -
AP (accelerator pedal) angle is computed by the PCM from the AP sensor voltage. AP angle should display "85-89%" at idle and "11-15%" at wide open throttle.

AP3 -Tech 2 Range 0%-100% -
AP (accelerator pedal) angle is computed by the PCM from the AP sensor voltage. AP angle should display "85-89%" at idle and "32-36%" at wide open throttle.

BAROMETRIC PRESSURE - Tech 2 Range 10-105 kPa/0.00-5.00 Volts -
The barometric pressure reading is determined from the MAP sensor signal monitored during key up and wide open throttle (WOT) conditions. The barometric pressure is used to compensate for altitude differences and is normally displayed around "61-104" depending on altitude and barometric pressure.

CHECK TRANS LAMP - AUTO TRANSMISSION -
Indicates the need to check for a DTC with the Tech 2 when the lamp is flashing 0.2 seconds ON and 0.2 seconds OFF.

DESIRED EGR POS. - Tech 2 Range 0%-100% -
Represents the EGR pintle position that the PCM is commanding.

DESIRED IDLE - Tech 2 Range 0-3187 RPM -
The idle speed that the PCM is commanding. The PCM will compensate for various engine loads based on engine coolant temperature, to keep the engine at the desired speed.

ECT - (Engine Coolant Temperature) Tech 2 Range -40 °C to 151 °C (-40 °F to 304 °F) -
The engine coolant temperature (ECT) is mounted in the coolant stream and sends engine temperature information to the PCM. The PCM applies 5 volts to the ECT sensor circuit. The sensor is a thermistor which changes internal resistance as temperature changes. When the sensor is cold (high resistance), the PCM monitors a high signal voltage and interprets that as a cold engine. As the sensor warms (decreasing resistance), the voltage signal will decrease and the PCM will interpret the lower voltage as a warm engine.

EGR DUTY CYCLE - Tech 2 Range 0%-100% -
Represents the EGR valve driver PWM signal from the PCM. A duty cycle of 0% indicates that no EGR flow is being commanded; a 100% duty cycle indicates maximum EGR flow commanded.

EGR FEEDBACK - Tech 2 Range 0.00-5.00 Volts -
Indicates the EGR pintle position sensor signal voltage being monitored by the PCM. A low voltage indicates a fully extended pintle (closed valve); a voltage near 5 volts indicates a retracted pintle (open valve).

ENGINE LOAD - Tech 2 Range 0%-100% -
Engine load is calculated by the PCM from engine speed and MAF sensor readings. Engine load should increase with an increase in RPM or air flow.

ENGINE RUN TIME - Tech 2 Range 00:00:00-99:99:99 Hrs:Min:Sec -
Indicates the time elapsed since the engine was started. If the engine is stopped, engine run time will be reset to 00:00:00.

ENGINE SPEED - Range 0-9999 RPM -
Engine speed is computed by the PCM from the 58X reference input. It should remain close to desired idle under various engine loads with engine idling.

EVAP PURGE PWM - Tech 2 Range 0%-100% -
Represents the PCM commanded PWM duty cycle of the EVAP purge solenoid valve."0%" displayed indicates no purge; "100%" displayed indicates full purge.

FUEL PUMP - Tech 2 Displays ON or OFF -
Indicates the PCM commanded state of the fuel pump relay driver circuit.

HO2S BANK 1, SEN. 1 - Tech 2 Range 0-1132 mV -
Represents the fuel control exhaust oxygen sensor output voltage. Should fluctuate constantly within a range between 10 mV (lean exhaust) and 1000 mV (rich exhaust) while operating in closed loop.

HO2S BANK 1, SEN. 2 - Tech 2 Range 0-1000 mV -
Monitors the exhaust oxygen sensor output voltage. The PCM monitors the operating efficiency of catalytic converter by comparing the output voltages of sensor 1 and sensor 2 in this bank. If the catalytic converter is operating efficiently, the output voltage of sensor 1 will give a greater fluctuation than that of sensor 2.If the PCM detects an abnormal level of voltage fluctuation from sensor 2, a DTC P0420 will be set, indicating that the catalytic converter for this bank is no longer operating efficiently.

HO2S BANK 2, SEN. 1 -Tech 2 Range 0-1132 mV-
Represents the fuel control exhaust oxygen sensor output voltage. Should fluctuate constantly within a range between 10 mV (lean exhaust) and 1000 mV (rich exhaust) while operating in closed loop.

HO2S BANK 2, SEN. 2-Tech 2 Range 0-1000 mV-
Monitors the exhaust oxygen sensor output voltage. The PCM monitors the operating efficiency of catalytic converter by comparing the output voltages of sensor 1 and sensor 2 in this bank. If the catalytic converter is operating efficiently, the output voltage of sensor 1 will have a greater fluctuation than that of sensor 2.If the PCM detects an abnormal level of voltage fluctuation from sensor 2, a DTC P0430 will be set, indicating that the catalytic converter for this bank is no longer operating efficiently.

HO2S BANK 1, SEN. 1-Tech 2 Displays NOT READY or READY-
Indicates the status of the exhaust oxygen sensor. The Tech 2 will indicate that the exhaust oxygen sensor is ready when the PCM detects a fluctuating HO2S voltage sufficient to allow closed loop operation. This will not occur unless the exhaust oxygen sensor is warmed up.

HO2S BANK 2, SEN. 1 - Tech 2 Displays NOT READY or READY -
Indicates the status of the exhaust oxygen sensor. The Tech 2 will indicate that the exhaust oxygen sensor is ready when the PCM detects a fluctuating HO2S voltage sufficient to allow closed loop operation. This will not occur unless the exhaust oxygen sensor is warmed up.

HO2S WARM UP TIME BANK 1, SEN. 1/BANK 1, SEN 2/BANK 2 SEN. 1/BANK 2 SEN. 2 -Tech 2 Range 00:00:00-99:99:99 HRS:MIN:SEC -
Indicates warm-up time for each HO2S. The HO2S warm-up time is used for the HO2S heater test. The PCM will run the heater test only after a cold start (determined by engine coolant and intake air temperature at the time of start-up) and only once during an ignition cycle. When the engine is started the PCM will monitor the HO2S voltage. When the HO2S voltage indicates a sufficiently active sensor, the PCM looks at how much time has elapsed since start-up. If the PCM determines that tool much time was required for the HO2S to become active, a DTC will set. If the engine was warm when started, HO2S warm-up will the display "00:00:00".

IAT (INTAKE AIR TEMPERATURE) - Tech 2 Range -40 °C to 151 °C (-40 °F to 304 °F) -
The PCM converts the resistance of the intake air temperature sensor to degrees. Intake air temperature (IAT) is used by the PCM to adjust fuel delivery and spark timing according to incoming air density.

IGNITION 1 - Tech 2 Range 0-25.5 Volts -
This represents the system voltage measured by the PCM at its ignition feed.

INJ. PULSE BANK 1/INJ. PULSE BANK 2 - Tech 2 Range 0-1000 msec. -
Indicates the amount of time the PCM is commanding each injector "ON" during each engine cycle. A longer injector pulse width will cause more fuel to be delivered. Injector pulse width should increase with increased engine load.

LONG TERM FUEL TRIM BANK 1/BANK 2 -
The long term fuel trim is derived from the short term fuel trim values and represents a long term correction of fuel delivery for the bank in question. A value of 0% indicates that fuel delivery requires no compensation to maintain the PCM commanded air/fuel ratio. A negative value significantly below 0% indicates that the fuel system is rich and fuel delivery is being reduced (decreased injector pulse width). A positive value significantly greater than 0% indicates that a lean condition exists and the PCM is compensating by adding fuel (increased injector pulse width). Because long term fuel trim tends to follow short term fuel trim, a value in the negative range due to canister purge at idle should not be considered unusual. Fuel trim values at maximum authority may indicate an excessively rich or lean system.

Fuel System STATUS - Tech 2 Displays OPEN or CLOSED -
"CLOSED" indicates that the PCM is controlling fuel delivery according to oxygen sensor voltage. In "OPEN" the PCM ignores the oxygen sensor voltage and bases the amount of fuel to be delivered on TP sensor, engine coolant, and MAF sensor inputs only.

MAF - Tech 2 Range 0.0-512 gm/s -
MAF (mass air flow) is the MAF input frequency converted to grams of air per second. This indicates the amount of air entering the engine.

MAP - Tech 2 Range 10-105 kPa (0.00-4.97 Volts) -
The manifold absolute pressure (MAP) sensor measures the change in the intake manifold pressure from engine load, EGR flow, and speed changes. As intake manifold pressure increases, intake vacuum decreases, resulting in a higher MAP sensor voltage and kPa reading. The MAP sensor signal is used to monitor intake manifold pressure changes during the EGR flow test, to update the BARO reading, and as an enabling factor for several of the diagnostics.

MIL - Tech 2 Displays ON or OFF -
Indicates the PCM commanded state of the malfunction indicator lamp.

MISFIRE CUR. CYL. #1 /#2 /#3 /#4 / #5 / #6 - Tech 2 Range 0-255 Counts -
The misfire current counters increase at a rate according to the number of the possible misfires being detected on each cylinder. The counters may normally display some activity, but the activity should be nearly equal for all the cylinders.

MISFIRE CUR. CYL. #1 /#2 /#3 /#4 / #5 / #6 - Tech 2 Range 0-65535 Counts -
The misfire history counters display the relative level of misfire that has been detected on each cylinder. The misfire history counters will not update or show any activity until a misfire DTC (P0300) has become active.

MISFIRE FAILURES SINCE FIRST FAIL - Tech 2 Range 0-65535 Counts -
Indicates the number of 200 crankshaft revolution sample periods during which the level of misfire was sufficiently high to report a fail.

MISFIRE PASSES SINCE FIRST FAIL - Tech 2 Range 0-65535 Counts -
Indicates the number of 200 crankshaft revolution sample periods during which the level of misfire was sufficiently low to report a pass.

POWER ENRICHMENT - Tech 2 Displays ACTIVE or INACTIVE -
"ACTIVE" displayed indicates that the PCM has detected conditions appropriate to operate in power enrichment mode. The PCM will command power enrichment mode when a large increase in throttle position and load is detected. While in power enrichment mode, the PCM will increase the amount of fuel delivered by entering open loop and increasing the injector pulse width. This is done to prevent a possible sag or hesitation from occurring during acceleration.

SPARK - Tech 2 Range -64 ° to 64 ° -
Displays the amount of spark advance being commanded by the PCM on the IC circuit.

START-UP ECT - Tech 2 Range -40 °C to 151 °C (-40 °F to 304 °F) -
Indicates the engine coolant temperature at the time that the vehicle was started. Used by the HO2S diagnostic to determine if the last start-up was a cold start.

START-UP IAT - Tech 2 Range -40 °C to 151 °C (-40 °F to 304 °F) -
Indicates the intake air temperature at the time that the vehicle was started. Used by the HO2S diagnostic to determine if the last start-up was a cold start.

TOTAL MISFIRE CURRENT COUNT - Tech 2 Range 0-255 -
Indicates the total number of cylinder firing events that were detected as being misfires during the last 200 crankshaft revolution sample period.

TP - Tech 2 Range 0%-100% -
TP (throttle position) angle is computed by the PCM from the TP sensor voltage. TP angle should display "3-5%" at idle and "100%" at wide open throttle.

CATALYST PROTECTION MODE - Tech 2 Displays YES or NO -
"YES" displayed indicates that the PCM has detected conditions appropriate to operate in TWC protection mode. The PCM will decrease the air/fuel ratio to a value that depends on mass air flow (higher mass air flow = lower air/fuel ratio).

UPSHIFT LAMP (MANUAL TRANSMISSION) VEHICLE SPEED - Tech 2 Range 0-255 km/h (0-155 mph) -
The vehicle speed sensor signal is converted into km/h and mph for display.

WEAK CYLINDER - Tech 2 Displays Cylinder Number -
This indicates that the PCM has detected crankshaft speed variations that indicate 2% or more cylinder firing events are misfires.