Scan Tool Diagnostics

A/C CLUTCH - Scan Tool Displays ON or OFF
Indicates whether the Powertrain Control Module ([1][2]PCM) has commanded the A/C clutch "ON". Used in A/C system diagnostics.

A/C REQUEST - Scan Tool Displays YES or NO
Indicates the state of the A/C request input circuit from the HVAC controls. The [1][2]PCM uses the A/C request signal to determine whether A/C compressor operation is being requested.

AIR/FUEL RATIO - Scan Tool Range 0.0 - 25.5
Air/fuel ratio indicates the [1][2]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.

BARO kPa - Scan Tool 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 scan tool when the lamp is flashing 0.2 seconds "ON" and 0.2 seconds "OFF".

CMP ACT COUNTER - Cam Position Activity

DECEL FUEL MODE - Scan Tool Displays ACTIVE or INACTIVE
"ACTIVE" displayed indicates that the [1][2]PCM has detected conditions appropriate to operate in deceleration fuel mode. The PCM will command the deceleration fuel mode when it detects a closed throttle position while the vehicle is traveling over 20 mph. While in the deceleration fuel mode, the PCM will decrease the amount of fuel delivered by entering open loop and decreasing the injector pulse width.

DESIRED EGR POS. - Scan Tool Range 0% - 100%
Represents the Exhaust Gas Recirculation (EGR) pintle position that the [1][2]PCM is commanding.

DESIRED IDLE - Scan Tool Range 0 - 3187 RPM
The idle speed that the [1][2]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) Scan Tool 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 [1][2]PCM. The PCM applies 5 volts to the ECT sensor circuit. The sensor is a thermistor which changes internal resistance as the 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 - Scan Tool Range 0% - 100%
Represents the EGR valve driver Pulse Width Modulate (PWM) signal from the [1][2]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 - Scan Tool Range 0.00 - 5.00 Volts
Indicates the EGR pintle position sensor signal voltage being monitored by the [1][2]PCM. A low voltage indicates a fully extended pintle (closed valve); a voltage near 5 volts indicates a retracted pintle (open valve).

EGR TEST COUNT - Scan Tool Range 0 - 255
Indicates the number of EGR flow test samples collected during the current ignition cycle. Under normal operation, only one sample is allowed during an ignition cycle. If the [1][2]PCM battery feed has been disconnected or a DTC P0401 has been cleared, 10 EGR flow test samples will be allowed during the ignition cycle. This is to allow repair verification during a single ignition cycle.

ENGINE LOAD - Scan Tool Range 0% - 100%
Engine load is calculated by the [1][2]PCM from Engine speed and MAF sensor readings. Engine load should increase with an increase in RPM or air flow.

ENGINE RUN TIME - Scan Tool 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 [1][2]PCM from the 58X reference input. It should remain close to desired idle under various Engine loads with Engine idling.

EVAP PURGE PWM - Scan Tool Range 0% - 100%
Represents the [1][2]PCM commanded PWM duty cycle of the EVAP purge solenoid valve. "0%" displayed indicates no purge; "100%" displayed indicates full purge.

EVAP VACUUM SWITCH - Scan Tool Displays PURGE or NO PURGE
The Evaporative Emission (EVAP) purge vacuum switch is a normally closed switch positioned in the purge line between the canister and the EVAP purge solenoid. The EVAP purge vacuum switch will open when vacuum increases to greater than 5 inches of water in the purge line. The EVAP purge vacuum switch is used by the [1][2]PCM to monitor EVAP canister purge solenoid operation and purge system integrity. The EVAP purge vacuum switch should be closed to ground with no vacuum present (0% EVAP purge PWM). With EVAP purge PWM at 25% or greater, the EVAP purge vacuum switch should be open and "PURGE" should be indicated.

FUEL PUMP - Scan Tool Displays ON or OFF
Indicates the [1][2]PCM commanded state of the fuel pump relay driver circuit.

FUEL TRIM CELL - Scan Tool Range 0 - 21
The fuel trim cell is dependent upon Engine speed and MAF sensor readings. A plot of RPM vs. MAF is divided into 22 cells. Fuel trim cell indicates which cell is currently active.

FUEL TRIM LEARN - Scan Tool Displays NO or YES
When conditions are appropriate for enabling long term fuel trim corrections, fuel trim learn will display "YES." This indicates that the long term fuel trim is responding to the short term fuel trim. If the fuel trim learn displays "NO," then long term fuel trim will not respond to changes in short term fuel trim.

HO2S BANK 1, SEN. 1 - Scan Tool 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 (Auto. Trans.) - Scan Tool Range 0 - 1000 mV
Represents the exhaust oxygen sensor output voltage. The [1][2]PCM monitors the operating efficiency of the 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 1, SEN. 2 (Manual Trans) - Scan Tool Range 0 - 1132 mV
Represents the 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. This is used along with HO2S Bank 1, Sensor 3 to determine the catalytic converter efficiency in the manual transmission models.

HO2S BANK 3, SEN. 3 (Manual Trans) - Scan Tool Range 0-1000 mV
Monitors the exhaust oxygen sensor output voltage. The [1][2]PCM monitors the operating efficiency of the catalytic converter by comparing the output voltages of sensor 2 and sensor 3. If the catalytic converter is operating efficiently, the output voltage of sensor 2 will gave greater fluctuation than that of sensor 3. If the PCM detects and abnormal level of voltage fluctuation from sensor 3, a DTC P0420 will be set, indicating that the catalytic converter is no longer operating efficiently.

HO2S BANK 2, SEN. 1 - Scan Tool 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 (Auto Trans) - Scan Tool Range 0-1000 mV
Monitors the exhaust oxygen sensor output voltage. The [1][2]PCM monitors the operating efficiency of the 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 P0430 will be set, indicating that the catalytic converter for this bank is no longer operating efficiently.

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

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

HO2S WARM UP TIME BANK 1, SEN. 1/BANK 1, SEN 2 (AUTO TRANS)/BANK 1, SEN. 2 (MANUAL TRANS)/BANK 1 SEN. 3 (MANUAL TANS)/BANK 2 SEN. 1/BANK 2 SEN. 2 (AUTO TRANS) - Scan Tool Range 00:00:00 - 99:99:99 HRS:MIN:SEC
Indicates warm-up time for each Heated Oxygen Sensor (HO2S). The HO2S warm-up time is used for the HO2S heater test. The [1][2]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 too 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 display "00:00:00."

IAC POSITION - Scan Tool Range 0 - 255 Counts
Displays the commanded position of the idle air control pintle in counts. A larger number of counts means that more air is being commanded through the idle air passage. Idle air control (IAC) should respond fairly quickly to changes in Engine load to maintain desired idle RPM.

IAT (INTAKE AIR TEMPERATURE) - Scan Tool Range -40°C to 151 °C (-40°F to 304°F)
The [1][2]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 - Scan Tool Range 0 - 25.5 Volts
This represents the system voltage measured by the [1][2]PCM at its ignition feed.

INJ. PULSE BANK 1 / INJ PULSE BANK 2 -Scan Tool Range 0 - 1000 msec.
Indicates the amount of time the [1][2]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.

KNOCK RETARD - Scan Tool Range 0.0 - 25.5
Indicates the amount of spark the [1][2]PCM is removing from IC spark advance in response to the signal from the knock sensors.

KS NOISE CHANNEL (Knock Sensor)
Indicates the output from the KS noise channel. There is always some electrical noise in an engine compartment and to avoid mistaking this as engine knock, the output from the knock sensor is compared to the output from the noise channel. A knock condition is not set unless the knock sensor output is greater than the noise channel output.

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 the fuel delivery requires no compensation to maintain the [1][2]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.

LOOP STATUS - Scan Tool Displays OPEN or CLOSED
"CLOSED" indicates that the [1][2]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 - Scan Tool Range 0.0-512 gm/s
Mass Air Flow (MAF) is the input frequency converted to grams of air per second. This indicates the amount of air entering the engine.

MAF INPUT FREQUENCY - Scan Tool Range 0-32000 Hz
The mass air flow sensor input signal to the [1][2]PCM is a frequency which varies from around 2500 Hz at idle to above 7000 Hz at wide open throttle. The PCM converts this frequency signal to grams per second to be displayed as mass air flow.

MAP - Scan Tool Range 10 -1O5 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 - Scan Tool Displays ON or OFF
Indicates the [1][2]PCM commanded state of the malfunction indicator lamp MIL) ("Check Engine Lamp").

MISFIRE CUR. CYL. # 1 / # 2 / # 3 / # 4 / # 5 / # 6 - Scan Tool Range 0-255 Counts
The misfire current counters increase at a rate according to the number of 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 - Scan Tool 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 - Scan Tool 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.

MISFIRE PASSES SINCE FIRST FAIL - Scan Tool 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 - Scan Tool Displays ACTIVE or INACTIVE
"ACTIVE" displayed indicates that the [1][2]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 the 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.

RICH/LEAN BANK 1 / BANK 2 - Scan Tool Displays RICH or LEAN
Indicates whether oxygen sensor voltage is above a 600 mV threshold voltage ("RICH") or below a 3000 mV threshold voltage ("LEAN"). Should change constantly while in closed loop, indicating that the [1][2]PCM is controlling the air/fuel mixture properly.

SHORT TERM FT BANK 1 / BANK 2
Short term fuel trim to a bank represents a short term correction to the bank fuel delivery by the [1][2]PCM in response to the amount of time the bank fuel control oxygen sensor voltage spends above or below the 450 mV threshold. If the oxygen sensor voltage has mainly remained less than 450 mV, indicating a lean air/fuel mixture, short term fuel trim will increase into the positive range above 0% and the PCM will pass fuel. If the oxygen sensor voltage stays mainly above the threshold, short term fuel trim will decrease below 0% into the negative range while the PCM reduces fuel delivery to compensate for the indicated rich condition. Under certain conditions such as extended idle and high ambient temperatures, canister purge may cause short term fuel trim to read in the negative range during normal operation. Fuel trim values at maximum authority may indicate an excessively rich or lean system.

SPARK - Scan Tool Range 640 to 640
Displays the amount of spark advance being commanded by the [1][2]PCM on the IC circuit.

START-UP ECT - Scan Tool Range -40°C to 151°C (-40°F to 304°F)
Indicates the Engine Coolant Temperature (ECT) 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 ECT - Scan Tool 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 - Scan Tool 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 ANGLE - Scan Tool Range 0% - 100%
Throttle Position (TP) angle is computed by the [1][2]PCM from the TP sensor voltage. TP angle should display "0%" at idle and "100%" at wide open throttle.

TP SENSOR - Scan Tool Range 0.00 - 5.00 Volts
The voltage being monitored by the [1][2]PCM on the TP sensor signal circuit.

TWC PROTECTION - Scan Tool Displays ACTIVE or INACTIVE
"ACTIVE" displayed indicates that the [1][2]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 - Scan Tool Range 0 - 255 km/h (0 - 155 mph)
The vehicle speed sensor (VSS) signal is converted into km/h and mph for display.

WEAK CYLINDER - Scan Tool Displays Cylinder Number
This indicates that the [1][2]PCM has detected Crankshaft speed variations that indicate 2% or more cylinder firing events are misfires.