Subaru 2009 IMPREZA Service Manual page 741

Diagnostic Trouble Code (DTC) Detecting Criteria
F: DTC P0037 HO2S HEATER CONTROL CIRCUIT LOW (BANK 1 SENSOR 2)
1. OUTLINE OF DIAGNOSIS
Detect the rear oxygen sensor heater open or short circuit.
The rear oxygen 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
Elapsed time after engine starting
Engine speed
4. GENERAL DRIVING CYCLE
After starting the engine, perform the diagnosis continuously when engine is low speed.
OFF
ON (D)
(B) Output voltage of the rear oxygen
sensor heater
Enable Condition
10.9 V
1 second
< 8000 rpm
GD(H4SO)-17
(C)
(C) 256 milliseconds (cycles)
GENERAL DESCRIPTION
EN-01792