Air / Fuel ImbalanceBank 1. Determines if a cylinder-to- cylinder air-fuel imbalance is present by monitoring the pre and post catalyst O2 sensor voltage characteristics. The pre voltage is used to generate a ratio metric. A normal system will generally result in a negative ratio while a failing system will generally result in a positive ratio. The post voltage is used to generate an X out of Y metric, where Y represents the number of samples and X represents the number of those samples that failed.
The front O2 sensor voltage is sampled once per cylinder event. Therefore, the time required to complete a single test (when all enable conditions are met) decreases as engine speed increases. For example, 9.0 seconds of data is required at 1000 rpm while double this time is required at 500 rpm and half this time is required at 2000 rpm.
Post O2 Feature Enabled: AND Filtered Post catalyst O2 voltage is NOT between
Intrusive cam AFM (DoD) AFM (DoD) and intrusive cam Post O2 testing
0 <= rpm <= 0
0 <= rpm <= 4800
for more than out of
Engine speed range is less than: during a short
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