Diagnostic Method

Fig 1: EVAP System Pressure Diagnosis Cycle Graph

Courtesy of SUBARU OF AMERICA, INC.

Fig 2: Evaporative Emission System Diagnosis Connection Diagram

Courtesy of SUBARU OF AMERICA, INC.

Mode A (Vacuum pump operation confirmation and characteristics stability) 

Purpose: Detect the vacuum pump operation trouble.

Judge as NG when the following conditions are established.

Judge as OK if the following conditions are not established, and warm up for five minutes to stabilize the vacuum pump characteristics.

Mode B (Measurement of reference pressure for setting the target negative pressure) 

1. Purpose: Judge the reference pressure stability.

   Judge as NG when the following conditions are established.

   JUDGMENT VALUE
   
   

   Malfunction Criteria	Threshold Value	DTC
   Pressure sensor maximum output value - Pressure sensor minimum output value	> 314 Pa (2.355 mmHg, 0.1 inHg)	P2404

2. Purpose: Judge whether the reference pressure is within the normal range, and detect the vacuum pump and orifice malfunctions.

   Judge as NG when the following conditions are established.

   JUDGMENT VALUE
   
   

   Malfunction Criteria	Threshold Value	DTC
   Reference pressure for setting the target negative pressure	< Value of Map 2	P2404
   	> Value of Map 3
   Reference pressure for judgment

   PRESSURE SPECIFICATION
   
   

   Barometric pressure kPa (mmHg, inHg)	70 (525, 20.7)	80 (600, 23.6)	90 (675, 26.6)	100 (750, 29.5)
   Reference pressure for setting the target negative pressure kPa (mmHg, inHg)	-4 (-29.79, -1.2)	-4.1 (-30.593, -1.2)	-4.2 (-31.395, -1.2)	-4.3 (-32.19, -1.3)

   BAROMETRIC PRESSURE SPECIFICATION
   
   

   Barometric pressure kPa (mmHg, inHg)	70 (525, 20.7)	80 (600, 23.6)	90 (675, 26.6)	100 (750, 29.5)
   Reference pressure for judgment kPa (mmHg, inHg)	-0.9 (-7.065, -0.3)	-1 (-7.86, -0.3)	-1.2 (-8.663, -0.3)	-1.3 (-9.465, -0.4)

Mode C (Switching valve operation confirmation) 

Purpose: Measure the pressure increase when switching valve is changed from open to close, and detect the stuck to open/close malfunctions of the switching valve.

Judge as NG when the following conditions are established.

Mode D (Clogging of pipe diagnosis and leak pressure measurement) 

1. Clogging of pipe 

   Purpose: Measure the time required for the evaporative emission system to reach the target negative pressure by the vacuum pump, and detect the clogging of pipe trouble.

   Judge as clogging of pipe malfunction if the evaporative emission system reaches to the target negative pressure within the specified time.

   JUDGMENT VALUE
   
   

   Malfunction Criteria	Threshold Value	DTC
   Time required to reach to the target negative pressure	≤ 27500 ms	P1451
   For target vacuum, use one of the followings. Reference pressure for target vacuum setting - value of Map 4 -5 kPa (-37.298 mmHg, -1.5 inHg)

   PRESSURE SPECIFICATION
   
   

   Time of negative pressure introduction ms	0	100000	200000	300000	400000	500000	600000	700000	800000	900000	1000000	1100000	1200000
   Reference pressure for setting the target negative pressure - Pressure sensor output value kPa (mmHg, inHg)	0.9 (7.058, 0.3)	0.9 (7.058, 0.3)	0.9 (7.058, 0.3)	0.9 (7.058, 0.3)	0.9 (7.058, 0.3)	0.9 (7.058, 0.3)	0.9 (7.058, 0.3)	0.9 (7.058, 0.3)	0.9 (7.058, 0.3)	0.9 (7.058, 0.3)	0.9 (7.058, 0.3)	0.9 (7.058, 0.3)	0.9 (7.058, 0.3)

2. Leak pressure measurement 

   Purpose: Measure the pressure (leak pressure) when the evaporative emission system becomes the negative pressure by the vacuum pump.

   Store the pressure as a leak pressure while the following conditions are met.

   JUDGMENT VALUE
   
   

   Conditions for storing the leak pressure	Threshold Value
   When any one of the followings is established:
   Reference pressure for setting the target negative pressure - Pressure sensor output value	≥ Value of Map 4
   Pressure sensor output value	< -5 kPa (-37.298 mmHg, -1.5 inHg)
   Time of negative pressure introduction	≥ 900000 ms

Mode E (Measurement of reference pressure for judgment) 

1. Purpose: Judge the reference pressure stability.

   Judge as NG when the following conditions are established.

   JUDGMENT VALUE
   
   

   Malfunction Criteria	Threshold Value	DTC
   Pressure sensor maximum output value - Pressure sensor minimum output value	> 314 Pa (2.355 mmHg, 0.1 inHg)	P2404

2. Purpose: Judge whether the reference pressure is within the normal range, and detect the vacuum pump and orifice malfunctions. Judge the vacuum pump performance stability.

   Judge as NG when the following conditions are established.

   JUDGMENT VALUE
   
   

   Malfunction Criteria	Threshold Value	DTC
   Reference pressure for judgment	< Value of Map 5	P2404
   	or
   	> Value of Map 6

   BAROMETRIC PRESSURE SPECIFICATION
   
   

   Barometric pressure kPa (mmHg, inHg)	70 (525, 20.7)	80 (600, 23.6)	90 (675, 26.6)	100 (750, 29.5)
   Reference pressure for judgment kPa (mmHg, inHg)	-4.5 (-34.02, -1.3)	-4.6 (-34.815, -1.4)	-4.7 (-35.618, -1.4)	-4.9 (-36.42, -1.4)

   BAROMETRIC PRESSURE SPECIFICATION
   
   

   Barometric pressure kPa (mmHg, inHg)	70 (525, 20.7)	80 (600, 23.6)	90 (675, 26.6)	100 (750, 29.5)
   Reference pressure for judgment kPa (mmHg, inHg)	-0.8 (-6.18, -0.2)	-0.9 (-6.983, -0.3)	-1 (-7.785, -0.3)	-1.1 (-8.58, -0.3)

3. Purpose: Judge the presence of evaporative emission system leak.

   Judge as NG when the following conditions are established.

   JUDGMENT VALUE
   
   

   Malfunction Criteria	Threshold Value	DTC
   < Large leak (0.04 inch) >		P0455
   Leak pressure	≥ lleakjdg (Pa)
   lleakjdg = (Reference pressure for judgment) X 0.377 - (-45.5 Pa)
   < Very small leak (0.02 inch) >		P0456
   Leak pressure	> Reference pressure of 0.018 inch
   	and
   	< lleakjdg (Pa)

Time Needed for Diagnosis:  Approx. 23 min

At next engine start, confirm whether the enable conditions are satisfied even though refueling has been done during soaking, and determine the malfunction.

Malfunction Indicator Light Illumination:  Illuminates when malfunction occurs in 2 continuous driving cycles.