DTC P0133: O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)

OUTLINE OF DIAGNOSIS
Detect time-lag of front oxygen (A/F) sensor response.

Front oxygen (A/F) sensor cover has some ventilation holes for exhaust gas. Clogged ventilation holes are diagnosed.

When the holes are clogged, the A/F output variation becomes slow comparing with the actual A/F variation because oxygen which reaches the zirconia layer is insufficient. Therefore, if the cover has clogged holes, the rich to lean judgment in ECM is delayed when the change from rich to lean is caused.

Fig 1: Identifying O2 Sensor
Courtesy of SUBARU OF AMERICA, INC.
COMPONENT DESCRIPTION

Fig 2: O2 Sensor Circuit Slow Response Graph
Courtesy of SUBARU OF AMERICA, INC.

ENABLE CONDITION

ENABLE CONDITION CHART

Secondary Parameters	Enable Conditions
All secondary parameter enable conditions	more than 1 second
Battery voltage	< 10.9 V
Atmospheric pressure	< 75.1 kPa (563 mmHg, 22.2 inHg)
Closed loop control with main feedback	operating
Impedance of front oxygen (A/F) sensor	0 <--> 50 Ω:
After engine starting	120 seconds or more
Engine coolant temperature	"GREATER THAN EQUAL TO" 75°C (167°F)
Engine speed	1000 <--> 3200 rpm
Vehicle speed	10 <--> 120 km/h (6.21 <--> 74.6 MPH)
Amount of intake air	10 <--> 31 g/s
Engine load change during 0.5 engine rev.	"GREATER THAN EQUAL TO" 0.02 g/rev
All conditions for EVAP canister purge	to be in enable
Learning value of EVAP conc. during purge	"GREATER THAN EQUAL TO" 0.2
Total time of operating canister purge	20 seconds or more

GENERAL DRIVING CYCLE
Perform the diagnosis only once at a constant speed of 10 to 120 km/h (6.21 to 74.6 MPH) in 120 seconds or more after vehicle starts to run with engine warmed-up.

DIAGNOSTIC METHOD

Integrate the difference of faf in every 128 milliseconds and difference of lambda value.

After integrate 1640 times (210 seconds), calculate the diagnosis value.

Judge NG when the malfunction criteria below are completed. Judge OK and clear NG when the malfunction criteria below are not completed.

Judgment Value

JUDGMENT VALUE CHART

Malfunction Criteria	Threshold Value
parafca = td2faf/td2lmd	"GREATER THAN EQUAL TO" 0.318
where, td2faf (N) = td2faf (n-1) + \|d2faf (n)\|
td2lmd (N) = td2lmd (n-1) + \|d2lmd (n)\| add up for a total of 210 seconds
d2faf (n) = (faf (n) - faf (n-1)) - (faf (n-1) - faf (n-2))
d2lmd (n) = (lmd (n) - lmd (n-1)) - (lmd (n-1) - lmd (n-2))
faf = main feedback compensation coefficient every 128 milliseconds
lmd = output lambda every 128 milliseconds

Time Needed for Diagnosis: 210 seconds

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

DTC CLEAR CONDITION
- When the OK idling cycle was completed 40 times in a row
- When "Clear Memory" was performed
MALFUNCTION INDICATOR LIGHT CLEAR CONDITION
- When the OK driving cycle was completed 3 times in a row
- When "Clear Memory" was performed
FAIL SAFE
- Front oxygen (A/F) sensor main learning correction: Not allowed to calculate.
- Correction when re-starting at high temperature: Normally minimum value 0.3 --> 0.
- Purge control: Not allowed to purge.
ECM OPERATING AT DTC SETTING
- Memorize the freeze frame data. (For test mode $02)
- Memorize the diagnostic value and trouble standard value. (For test mode $06)