DTC Advanced Diagnostics: P0686
DTC P0686:A/F Sensor (Sensor 1) Heater Power Source Circuit Short to Ground

General Description

A heater for the sensor element is embedded in the air/fuel ratio (A/F) sensor (sensor 1), and it is controlled and monitored by the powertrain control module (PCM). It is activated and heats the sensor to stabilize and speed up the detection of oxygen content when the exhaust gas temperature is cold. If the FI SUB RLY CL- voltage is a specified range, the PCM detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type
Execution
Continuous
Sequence
None
Duration
0.3 second or more
DTC Type
Two drive cycles, MIL on

Enable Conditions
Condition
Minimum
Maximum
12 volt battery voltage [Battery]
8 V
16 V
Vehicle
ON mode
Command to A/F sensor (sensor 1) heater relay
OFF
[ ]: HDS Parameter

Malfunction Threshold
The FI SUB RLY CL- voltage is 2.74 or less.

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.
PGM-FI subrelay circuit FI SUB RLY CL- line short to ground

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.