Monitor A1

WARNING: This page is about a different variant/trim than selected.

When there is an air-fuel ratio cylinder imbalance malfunction, the primary oxygen sensor output fluctuates widely compared with a normal sensor, as shown by the chain line in Fig 1 below. This monitor makes a diagnosis based on this phenomenon. Each primary oxygen sensor signal (PS) and mean value of the primary oxygen sensor signal (MS) is calculated from the primary oxygen sensor signal. The absolute values of (PS - MS) are sampled every 4 ms as shown in the figure. Diagnostic value 1 (DV1) is obtained by integrating the absolute value of (PS - MS) for 2500 times. A malfunction is determined when DV1 exceeds the threshold. The judgment values are determined experimentally.

Fig 1: Comparision Malfunctioned Primary Oxygen Sensor Output With Normal Sensor

Courtesy of SUBARU OF AMERICA, INC.

Judge as NG when the following conditions are established.

JUDGMENT VALUE

Malfunction Criteria	Threshold Value
Diagnostic value 1 (DV1)	> Threshold value 1 (TV1)

Fig 1: Identifying Threshold Value

Courtesy of SUBARU OF AMERICA, INC.

MAP (AT MODEL)

		Engine load (g/rev (oz/rev))
		0.9 (0.03)	1 (0.04)	1.1 (0.04)	1.2 (0.04)	1.3 (0.05)
Engine speed (rpm)	1400	0.002461	0.003704	0.003704	0.003704	0.003704
	1600	0.002637	0.002926	0.003214	0.003214	0.003214
	1800	0.003419	0.003461	0.003465	0.003465	0.003465
	2000	0.002197	0.002636	0.003468	0.003468	0.003468
	2200	0.003581	0.004258	0.005648	0.005648	0.005648
	2400	0.002227	0.003214	0.003826	0.003826	0.003826
	2600	0.002535	0.003096	0.003281	0.003281	0.003281
	2800	0.002261	0.002688	0.003218	0.003218	0.003218

MAP (MT MODEL)

		Engine load (g/rev (oz/rev))
		0.9 (0.03)	1 (0.04)	1.1 (0.04)	1.2 (0.04)	1.3 (0.05)
Engine speed (rpm)	1400	0.001612	0.002426	0.002426	0.002426	0.002426
	1600	0.002604	0.002889	0.003174	0.003174	0.003174
	1800	0.001632	0.001892	0.001892	0.001892	0.001892
	2000	0.001625	0.001949	0.002229	0.002229	0.002229
	2200	0.003158	0.003755	0.004980	0.004980	0.004980
	2400	0.001600	0.001600	0.003561	0.003561	0.003561
	2600	0.001869	0.001869	0.001869	0.001869	0.001869
	2800	0.001869	0.001869	0.001869	0.001869	0.001869

Time Needed for Diagnosis :

4 ms x 4000 time(s) (AT model)
4 ms x 2500 time(s) (MT model)

Judge as OK and clear the NG if the following conditions are established.

JUDGMENT VALUE

Malfunction Criteria	Threshold Value
Diagnostic Value1 (DV1)	≥ Value from Map

Time Needed for Diagnosis :

4 ms x 4000 time(s) (AT model)
4 ms x 2500 time(s) (MT model)