Misfire Data

MISFIRE CUR. #1/ MISFIRE CUR. #2 / MISFIRE CUR. #3 / MISFIRE CUR. #4 / MISFIRE CUR. #5 / MISFIRE CUR. #6 - Scan Tool Range 0-255 Counts
The Misfire Current counters increment at a rate according to the number of possible misfires being detected on each cylinder during the last 200 cylinder firing events. The counters may normally display some activity, but the activity should be nearly equal for all the cylinders.

MISFIRE HIST. #1/ MISFIRE HIST. #2/ MISFIRE HIST. #3/ MISFIRE HIST. #4/ MISFIRE HIST. #5. MISFIRE HIST. #6- Scan Tool Range 0-65535 Counts
The Misfire History counters display the total level of misfire that has been detected on each cylinder. The Misfire History counters will not update or show any activity until a misfire Diagnostic Trouble Code (DTC) (P0300) has become active. The Misfire History counters will update every 200 cylinder firing events.

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 high to report a fail.

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.

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.

ECT - Scan Tool Range -40°C to 151°C, -40°F to 304°F
The Engine Coolant Temperature (ECT) sensor 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 (internal resistance high), the PCM monitors a high signal voltage and interprets it 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.

HOT OPEN LOOP - Scan Tool Displays ACTIVE or INACTIVE
ACTIVE displayed indicates that the PCM has detected conditions appropriate to operate in Hot Open Loop mode. The PCM determines this based on Engine Coolant Temperature, Mass Air Flow and Vehicle Speed. While in Hot Open Loop, the PCM will take actions such as increasing injector pulse width to avoid an engine overheat situation,.

LOOP STATUS - Scan Tool Displays OPEN or CLOSED
"Closed Loop" 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 Throttle Position (TP) sensor, engine coolant, and Mass Air Flow (MAF) sensor inputs only.

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 short term fuel trim. If the Fuel Trim Learn displays "NO," long term fuel trim will not respond to changes in short term fuel trim.

HEATED OXYGEN SENSORS (HO2S BN1 SEN. 1 and HO2S BN2 SEN. 1) - Scan Tool Displays NOT READY or READY
Indicates the status of the exhaust oxygen sensors. The scan tool will indicate that the exhaust oxygen sensors are ready when the PCM detects a fluctuating Heated Oxygen Sensor (HO2S) voltage sufficient to allow closed loop operation. This will not occur unless the exhaust oxygen sensors are warmed up.

RICH/LEAN BN1 and BN2 - Scan Tool Displays RICH or LEAN
Indicates whether oxygen sensor voltage is above a 600 mV threshold voltage (rich) or below a 300 mV threshold voltage (lean). Should change constantly while in closed loop, indicating that the PCM is controlling the air/fuel mixture properly.

HO2S XCOUNTS BN1 / HO2S XCOUNTS BN2 - Scan Tool Range 0-255
Indicates the number of times each HO2S signal has crossed the 450mV bias voltage during a 1 second interval. A HO2S signal that almost never crosses the bias voltage could indicate a fuel trim problem, a faulty HO2S circuit, or a faulty HO2S.

SHORT TERM FUEL TRIM BN1 - Scan Tool Range -11% to 20%
Short Term Fuel Trim BN1 represents a short-term correction to bank 1 fuel delivery by the PCM in response to the amount of time the bank 1 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 add 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. The PCM's maximum authority to control fuel trim allows a range between -11% and +20%. Fuel trim values at maximum authority may indicate an excessively rich or lean system.

LONG TERM FUEL TRIM BN1 - Scan Tool Range -23% to 16%
Long Term Fuel Trim BN1 is derived from the Short Term Fuel Trim BN1 value and represents a long-term correction of bank 1 fuel delivery. 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. The PCM's maximum authority to control fuel trim allows a range between -23% and +16%. Fuel trim values at maximum authority may indicate an excessively rich or lean system.

SHORT TERM FUEL TRIM BN2- Scan Tool Range -11% to 20%
Short Term Fuel Trim BN2 represents a short-term correction to bank 2 fuel delivery by the PCM in response to the amount of time the bank 2 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 add 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. The PCM's maximum authority to control fuel trim allows a range between -11% and +20%. Fuel trim values at maximum authority may indicate an excessively rich or lean system.

LONG TERM FUEL TRIM BN2 - Scan Tool Range -23% to 16%
Long Term Fuel Trim BN2 is derived from the Short Term Fuel Trim BN2 value and represents a long-term correction of bank 2 fuel delivery. 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. The PCM's maximum authority to control fuel trim allows a range between -23% and +16%. Fuel trim values at maximum authority may indicate an excessively rich or lean system.

FUEL TRIM CELL - Scan Tool Range 0-9
Fuel trim cell is dependent upon engine speed and MAF sensor readings. A plot of RPM vs. MAF is divided into 10 cells. Fuel trim cell indicates which cell is currently active.

ENGINE LOAD - Scan Tool Range 0% to 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 airflow.

IGNITION MODE - Scan Tool Displays BYPASS or IC
Indicates the commanded state of the Bypass signal output from the PCM. When BYPASS is displayed ,the PCM allows the ignition control module to keep the spark advance at a fixed 10 BTDC. IC displayed indicates that the PCM has signaled the ignition module that the PCM is going to control the spark advance (IC mode). The ignition control module determines the correct operating mode based on the level of voltage that the PCM sends to the ignition control module on the bypass circuit. The PCM provides 5 volts to the ignition control module if the PCM is going to control spark timing (IC mode). If the PCM does not turn "ON" the 5 volts, or if the ignition control module doesn't receive it, the module will keep control of spark timing (Bypass mode).

SPARK - Scan Tool Range -64 to 64
Displays the amount of spark advance being commanded by the PCM on the IC circuit. Because the ignition control module sets spark advance at a fixed value of 10 BTDC while operating in Bypass mode, the displayed Spark advance only reflects true spark timing when the PCM has commanded IC mode.

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

DESIRED EGR POS. - Scan Tool Range 0% to 100%
Represents the EGR pintle position that the PCM is commanding. Desired EGR Pos. should stay close to Actual EGR Pos.

ACTUAL EGR POS - Scan Tool Range 0% to 100%
Represents the actual position of the EGR pintle in percent. 0% displayed indicates a fully extended pintle (EGR valve closed).

VEHICLE SPEED - Scan Tool Range 0-255 km/h, 0-155 mph
The vehicle speed sensor signal is converted into km/h and mph for display.

CURRENT GEAR - Scan Tool Displays 1, 2, 3, or 4
The PCM looks at Trans Range position and the gear commanded by the PCM. The actual forward gear that the transmission is in will be the lower of the two because the manual valve can override the PCM commanded gear.

ENGINE SPEED - Range 0-9999 RPM
Engine speed is computed by the PCM from the 3X reference input. It should remain close to desired idle under various engine loads with engine idling.

COMMANDED TCC - Scan Tool Displays ENGAGED or DISENGAGED
Represents the PCM commanded state of the transmission torque converter clutch.

IAC POSITION - Scan Tool Range 0-255
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 should respond fairly quickly to changes in engine load to maintain desired idle RPM.

TWC PROTECTION - Scan Tool Displays ACTIVE or INACTIVE
ACTIVE displayed indicates that the PCM has detected conditions appropriate to operate in TWC Protection mode. This is determined based on Engine Load and Engine Coolant Temperature. While in TWC Protection, the PCM will decrease Air/Fuel Ratio to a value that depends on Mass Air Flow (higher Mass Airflow = lower Air/Fuel Ratio).

DECEL FUEL MODE - Scan Tool Displays ACTIVE or INACTIVE
ACTIVE displayed indicates that the PCM has detected conditions appropriate to operate in Deceleration Fuel mode. The PCM will command deceleration fuel mode when a sudden decrease in throttle position has been detected while the vehicle is traveling over 20 mph. While in Deceleration Fuel mode, the PCM will decrease the amount of fuel delivered by entering Open Loop and decreasing the injector pulse width.

POWER ENRICHMENT - Scan Tool 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, 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.

A/C REQUEST - Scan Tool 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.

COMMANDED A/C - Scan Tool Displays ON or OFF
Represents the PCM commanded state of the A/C compressor clutch relay driver circuit. The A/C compressor clutch should be engaged when Commanded A/C displays ON.