Cold Start Emission Reduction Monitor

COLD START EMISSION REDUCTION MONITOR

Overview
The cold start emission reduction monitor is being introduced to meet the low emissions vehicle-II (LEV-II) emissions standards. The monitor works by validating the operation of the components of the system required to achieve the cold start emission reduction strategy, retarded spark timing and elevated idle airflow.

Low Idle Airflow Test
When the cold start emission reduction monitor is enabled, the idle air control system requests a higher RPM, elevating engine airflow. While this cold start emission reduction elevated airflow is requested, the low airflow test compares the measured idle airflow from the mass air flow (MAF) sensor to the commanded idle air control strategy. For the purpose of detecting low airflow failures, the low airflow test uses the measured airflow and the commanded airflow to create a low airflow index.

Cold start emission reduction low airflow test operation:
- DTC: P050A cold start idle air control system performance
- Monitor execution: Once per driving cycle, from start up with the cold start emissions reduction active
- Monitor sequence: none
- Monitoring duration: 7 seconds

Spark Timing Monitor
The powertrain control module (PCM) is equipped with a spark conduction capture circuit which measures the timing and duration of the spark delivered by processing the flyback voltage signal from the primary side of the ignition coil. With the cold start emission reduction monitor enabled, the spark control strategy requests retarded spark timing. While retarded spark timing is requested, the spark timing monitor compares the measured spark timing from the spark conduction capture circuit to the commanded spark timing from the spark control strategy. For the purpose of detecting spark timing failures, the spark timing monitor increments a fault filter if the measured spark timing is advanced by more than 5 degrees from the commanded spark timing. A failure is indicated if the fault filter exceeds a value of 200, equivalent to a failure duration of approximately 4 seconds.

Cold start emission reduction typical spark timing test entry conditions:
- DTC: P050B cold start ignition timing performance
- Monitor execution: Once per driving cycle, from startup with cold start emission reduction monitor active
- Monitor sequence: none
- Monitoring duration: 7 seconds
- Minimum entry condition: 400 RPM
- Maximum entry condition: 2,000 RPM

Cold start emission reduction typical spark timing test malfunction thresholds:
- Spark advanced from desired is greater than 5 degrees
- Malfunction present for 4 seconds