Three -Way Catalyst Data
TWC MONITOR TEST COUNTER - Scan Tool Range 0-49The Three Way Catalyst (TWC) monitor test counter increments while the TWC system diagnostic test is running and taking samples. When the TWC Monitor Test Counter reaches 49, the PCM will update the TWC diagnostic statistical filter. At this point, the TWC Monitor Test Counter will reset to 0 and begin incrementing again The TWC Monitor Test Counter is most useful when verifying a three-way catalytic converter replacement or any repair associated with the DTC P0420 diagnostic table.
TWC Diagnostic - Scan Tool Displays ENABLED or DISABLED
ENABLED displayed indicates that Mass Air Flow (MAF), Heated Oxygen Sensor (HO2S), Engine Coolant Temperature (ECT) or Vehicle speed Sensor (VSS) DTCs that would disable the TWC diagnostic are not present.
ENGINE SPEED - Scan Tool 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.
ECT - Scan Tool Range -40°C to 151°C, (-40°F to 304°F)
The Engine Coolant Temperature 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.
IAT - Scan Tool 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.
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.
TP ANGLE - Scan Tool Range 0- 100%
Throttle Position (TP) Angle is computed by the PCM from the TP sensor voltage. TP Angle should display 0% at idle and 100% at wide open throttle.
TP SENSOR - Scan Tool Range 0.0-5.00 Volts
The voltage being monitored by the PCM on the TP sensor signal circuit.
THROTTLE AT IDLE - Scan Tool Displays YES or NO
Indicates whether the TP Angle being monitored by the PCM is at 0% when the throttle is closed. Refer to DTC P0121 if TP sensor angle is not 0% with the throttle closed. P0121
MAF - Scan Tool 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.
ENGINE LOAD - Scan Tool 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 airflow.
AIR FUEL RATIO - Scan Tool Range 0.0- 25.5
Air Fuel Ratio indicates the PCM commanded value. In closed loop, Air Fuel Ratio should normally be 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 Decel Fuel Mode.
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.
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 TP sensor, engine coolant, and 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 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.
HEATED OXYGEN SENSORS (HO2S BN1 SEN. 2 and HO2S BN2 SEN. 3) - Scan Tool Range 0-1132 mV
Represents the catalyst monitor exhaust oxygen sensor output voltage If the catalyst is operating efficiently, the Bank 1 Heated Oxygen Sensor (HO2S) 2 signal will be far more active than that produced by the Bank 1 HO2S 3 sensor. If the PCM detects a level of Bank 1 HO2S 3 activity that indicates the catalyst is no longer operating efficiently, DTC P0420 will be set.
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.
MIL - Scan Tool Displays ON or OFF
Indicates the PCM commanded state of the Malfunction Indicator Lamp.
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.
INJ. PULSE WIDTH - Scan Tool Range 0-1000m sec.
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. Inj. Pulse Width should increase with increased engine load.
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.