Catalytic Monitor

Catalytic Monitor Data

Engine Speed - Range 0 - 16384 RPM: Engine Speed is computed by the PCM from the fuel control reference input. It should remain close to desired idle under the various engine loads with the engine idling.

Desired Idle - 0 - 3187 RPM: The PCM commands the idle speed. The PCM compensates for various engine loads in order to maintain the desired idle speed. The actual RPM's engine speed should remain close to the desired idle under the various engine loads with the engine idling.

ECT - Range -40°C - 151°C (-40°F - 304°F): The Engine Coolant Temperature (ECT) sensor sends engine 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 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.

IAT - Range -40°C - 151°C (-40°F - 304°F): The PCM converts the resistance of the Intake Air Temperature (IAT) sensor to degrees in the same manner as the ECT sensor. Intake air temp is used by the PCM to adjust fuel delivery and spark timing according to incoming air density.

MAP - Range 11 - 105 kPa, 0 - 5.0 Volts: The Manifold Absolute Pressure (MAP) sensor measures the change in the intake manifold pressure which results from engine load and speed changes. As the intake manifold pressure increases, the air density in the intake also increases and additional fuel is required.

BARO - Range 11 - 105 kPa, 0 - 5.0 Volts: The Barometric Pressure (BARO) sensor measures the change in the intake manifold pressure which results from altitude changes. This value is updated at ignition ON and also at Wide Open Throttle (WOT).

TP Sensor - Range 0.0 - 0.5 Volts: The PCM uses the Throttle Position (TP) sensor to determine the amount of the throttle demanded by the operator of the vehicle. The TP sensor reads between 0.36 - 0.96 volt at idle to above 4.0 volts at Wide Open Throttle (WOT).

TP Angle - Range 0 - 100%: The PCM computes the Throttle Position (TP) from the TP sensor voltage input. The TP angle will auto zero to 0% at idle when the TP voltage is below 0.90 volt. The TP angle will read 100% at Wide Open Throttle (WOT).

Engine Run Time - Range 0:00:00 - 18:12:15 hours:minutes:seconds: A measure of how long the engine has been running. When the engine stops running, the timer is reset to zero.

# of Catalyst Mon Test Completed - Range 0 - 255: The Catalyst Mon. Test completed sample counter is the total number of test samples this ignition cycles. The Samples counter should never indicate greater than 1 unless the technician has cleared a DTC or disconnected the battery.

Loop Status - Range Open/Closed: A Closed Loop displayed indicates that the PCM is controlling the fuel delivery according to the Oxygen Sensor (O2S 1) voltage. The PCM controls the fuel delivery air to fuel ratio as close to 14.7:1 as possible.

Catalyst Converter TT: Represents the temperature of the Catalytic Converter. Useful for determining if the Catalyst Monitor test has run.

Calc. Air Flow - Range 0 - 512 grams/second: The calculated air flow is a calculation based on manifold absolute pressure. The calculation is used in several diagnostics to determine when to run.

Short Term FT - Range 0 - 255 (-100% to 100%): Short Term Fuel Trim (FT) 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 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.

02S 1 - Range 0 - 1132 mV: The Oxygen Sensor (O2S 1) reading represents the exhaust oxygen sensor output voltage. This voltage will fluctuate constantly between 100 mV (lean exhaust) to 900 mV (rich exhaust) when operating in a Closed Loop.

HO2S 2 - Range 0 - 1132 mV: The Rear Heated Oxygen Sensor (HO2S 2) represents the exhaust oxygen output voltage past the catalytic converter. This voltage remains inactive, or the voltage will appear lazy within a range of 100 mV (lean exhaust) and 900 mV (rich exhaust) when the system is operating in a Closed Loop.