On-Board Diagnostics: Monitors

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2001 Saturn SW2, 2001 Saturn SL2, 2001 Saturn SL1, 2001 Saturn SL, and 2001 Saturn SC2. However, it is still accessible from the selected car via links, so may be relevant.

Comprehensive Component Monitor

Monitors PCM systems for opens, shorts, grounds and out-of-range sensors. Also monitors rationality of sensors. Rationality is whether the sensors value is consistent with the operating conditions of the other sensors.

Misfire Monitor

Monitors engine misfire using crankshaft sensor to determine location and severity of misfire. A catalyst damaging misfire will flash the MIL, and a non-catalyst damaging misfire is a normal type "B" code.

Fuel Trim Monitor

Monitors short and long term fuel trim for being at maximum lean or rich limit.

Oxygen Sensor Monitor

Monitors all oxygen sensors for maximum voltage level, minimum voltage level and lean rich/rich lean switching rate.

Oxygen Sensor Heater Monitor

Monitors oxygen sensor heater by watching sensor's time to activity after a cold start.

Catalyst Monitor

Monitors catalyst efficiency by comparing activity rate of precatalyst oxygen sensor and postcatalyst oxygen sensor.

EVAP Monitor

Monitors EVAP system for large leaks, small leaks and purge flow.

Secondary Air Monitor

Monitors secondary air operation.