Subaru 2009 IMPREZA Service Manual page 737

Diagnostic Trouble Code (DTC) Detecting Criteria
D: DTC P0031 HO2S HEATER CONTROL CIRCUIT LOW (BANK 1 SENSOR 1)
1. OUTLINE OF DIAGNOSIS
Detect front oxygen (A/F) sensor heater open or short circuit.
The front oxygen (A/F) sensor heater performs duty control, and the output terminal voltage at ON is 0 V, and
the output terminal voltage at OFF is the battery voltage.
Judge as NG when the terminal voltage remains Low.
2. COMPONENT DESCRIPTION
(A)
(B)
0V
(A) Battery voltage
(D) Low error
3. ENABLE CONDITIONS
Secondary Parameters
Battery voltage
4. GENERAL DRIVING CYCLE
Always perform the diagnosis continuously.
OFF
ON (D)
(C)
(B) Front oxygen (A/F) sensor heater
output voltage
Enable Condition
10.9 V
GD(H4SO)-13
GENERAL DESCRIPTION
(C) 128 milliseconds
EN-01792