On-Board Diagnostics: Monitors
WARNING: This page is about a different car, the 2003 GMC Savana and 2003 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
Not all monitors will run while operating in CNG mode. In order to complete all monitors, the vehicle will also need to operate in gasoline mode.
- 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 pre-catalyst oxygen sensor and post-catalyst oxygen sensor. - EVAP Monitor
Monitors EVAP system for large leaks, small leaks and purge flow.