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

General Description

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) SO2HTB2 line open
Front secondary HO2S (bank 2, sensor 2) SO2HTB2 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
Keyless access control unit malfunction
PCM internal circuit failure

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.