Subaru Impreza 2005 General Description Manual page 17

Diagnostic Trouble Code (DTC) Detecting Criteria
F: DTC P0037 HO2S HEATER CONTROL CIRCUIT LOW (BANK 1 SENSOR 2)
1. OUTLINE OF DIAGNOSIS
Detect open or short circuit of rear oxygen sensor heater.
Rear oxygen sensor heater conducted the duty control, and the output terminal voltage at ON is 0 V and the
output terminal voltage at OFF is the battery voltage.
Judge NG when the terminal voltage remains to be Low.
2. COMPONENT DESCRIPTION
(A)
(B)
0V
(A) Battery voltage
(B) Rear oxygen sensor heater output voltage
(C) 256 milliseconds (cycles)
(D) Low malfunction
3. ENABLE CONDITION
Secondary Parameters
Battery voltage
Elapsed time after engine starting
4. GENERAL DRIVING CYCLE
Perform the diagnosis continuously in 1 second after engine starting.
5. DIAGNOSTIC METHOD
• Abnormality Judgment
Judge NG when the continuous time of completing all the malfunction criteria below becomes more than
2,560 millisecond (10 cycles).
Judgment Value
Malfunction Criteria
Output voltage level
Rear oxygen sensor heater control duty
Time Needed for Diagnosis: 2.56 seconds
Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cy-
cles.
OFF
ON (D)
Enable Conditions
> 10.9 V
≥ 1 second
Threshold Value
Low
< 75%
GD(STi)-17
(C)
GENERAL DESCRIPTION
EN-01792