Comprehensive Component Monitor Diagnostic Operation

COMPREHENSIVE COMPONENT MONITOR DIAGNOSTIC OPERATION
Comprehensive component monitoring diagnostics are required to monitor emissions-related input and output powertrain components.

Input Components
Input components are monitored for circuit continuity and out-of-range values. This includes rationality checking. Rationality checking refers to indicating a fault when the signal from a sensor does not seem reasonable, i.e. Throttle Position (TP) sensor that indicates high throttle position at low engine loads or Manifold Absolute Pressure (MAP) voltage. Input components may include, but are not limited to, the following sensors:
- Vehicle Speed Sensor (VSS)
- Crankshaft Position (CKP) sensor
- Throttle Position (TP) sensor
- Engine Coolant Temperature (ECT) sensor
- Camshaft Position (CMP) sensor
- Manifold Absolute Pressure (MAP) sensor

In addition to the circuit continuity and rationality check, the ECT sensor is monitored for its ability to achieve a steady state temperature to enable closed loop fuel control.

Output Components
Output components are diagnosed for proper response to control module commands. Components where functional monitoring is not feasible will be monitored for circuit continuity and out-of-range values if applicable. Output components to be monitored include, but are not limited to the following circuit:
- Idle Air Control (IAC) Motor
- Control module controlled EVAP Canister Purge Valve
- A/C relays
- Cooling fan relay
- VSS output
- MIL control
- Cruise control inhibit

Refer to "Powertrain Control Module/Engine Control Module" and Sensors.

Passive and Active Diagnostic Tests
A passive test is a diagnostic test which simply monitors a vehicle system or component. Conversely, an active test, actually takes some sort of action when performing diagnostic functions, often in response to a failed passive test. For example, the Exhaust Gas Recirculation (EGR) diagnostic active test will force the EGR valve open during closed throttle deceleration and/or force the EGR valve closed during a steady state. Either action should result in a change in manifold pressure.

Intrusive Diagnostic Tests
This is any on-board test run by the Diagnostic Management System which may have an effect on vehicle performance or emission levels.

Warm-Up Cycle
A warm-up cycle means that engine temperature must reach a minimum of 70 °C (160 °F) and rise at least 22 °C (72 °F) over the course of a trip.

Freeze Frame
Freeze Frame is an element of the Diagnostic Management System which stores various vehicle information at the moment an emissions-related fault is stored in memory and when the Malfunction Indicator Lamp (MIL) is commanded on. These data can help to identify the cause of a fault.

Failure Records
Failure Records data is an enhancement of the OBD II Freeze Frame feature. Failure Records store the same vehicle information as does Freeze Frame, but it will store that information for any fault which is stored in on- board memory, while Freeze Frame stores information only for emission-related faults that command the MIL on.