DTC P0161

DTC P0161: Front Secondary Heated Oxygen Sensor (Secondary HO2S (Bank 2, Sensor 2)) Heater Circuit Malfunction

General Description

Courtesy of HONDA, U.S.A., INC.

A heater for the zirconia element is embedded in the front secondary heated oxygen sensor (secondary HO2S (bank 2, sensor 2)), and it is controlled by the powertrain control module (PCM). When activated, it heats the sensor to stabilize and speed up the detection of oxygen content when the exhaust gas temperature is cold. If the front secondary HO2S (bank 2, sensor 2) heater draws other than a specified amperage, the PCM detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type, OBD Status

Execution	Continuous
Sequence	None
Duration	5.0 seconds or more
DTC Type	Two drive cycles, MIL on
OBD Status	PASSED/FAILED/NOT COMPLETED (STILL TESTING)

Enable Conditions

Condition	Minimum	Maximum
Battery voltage [BATTERY] (IGP terminal of PCM)	10.5 V	-
State of the engine	Running
No active DTCs set (prevents monitor from running)	P0117, P0118

[ ]: HDS Parameter

Malfunction Threshold

The front secondary HO2S (bank 2, sensor 2) heater output is 0.38 A or less, or 3.33 A or more, for at least 5.0 seconds when the heater is on.

Possible Cause

NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.

Front secondary HO2S (bank 2, sensor 2) heater failure
Front secondary HO2S (bank 2, sensor 2) SO2HT B2 line open
Front secondary HO2S (bank 2, sensor 2) SO2HT B2 line short to ground
Front secondary HO2S (bank 2, sensor 2) heater power supply line open (includes fuse blown)
Front secondary HO2S (bank 2, sensor 2) heater internal circuit open
Poor ignition switch
PCM internal circuit failure

Confirmation Procedure

Operating Condition

Start the engine, and let it idle until the radiator fan comes on.

With the HDS

None.

Diagnosis Details

Conditions for setting the DTC

When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC and the freeze data are stored.

Conditions for clearing the DTC

The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command or by disconnecting the battery.