DTC Advanced Diagnostics: P2627
DTC P2627:Rear Air/Fuel Ratio (A/F) Sensor (Bank 1, Sensor 1) LABEL Circuit Low Voltage

General Description

The rear air/fuel ratio (A/F) sensor (bank 1, sensor 1) is installed in the exhaust manifold and detects oxygen content in the exhaust gas. The rear A/F sensor (bank 1, sensor 1) transmits a signal to the powertrain control module (PCM), and it enables overall feedback control. The PCM controls fuel injection duration by comparing the target air/fuel ratio with the rear A/F sensor (bank 1, sensor 1) signal. The rear A/F sensor (bank 1, sensor 1) has a built-in LABEL resistance to regulate the difference of the sensor characteristics. The PCM reads the resistance to regulate the difference properly. If the LABEL resistance (VLBLB1 signal voltage) is a set value or less, the PCM detects a malfunction and stores a DTC.

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

Enable Conditions
Condition
 
Engine start/stop button
ON mode
No active DTCs set (prevents monitor from running)
P2628

Malfunction Threshold
The VLBLB1 voltage is 0.3 V or less for at least 5 seconds.

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.
Rear A/F sensor (bank 1, sensor 1) failure
Rear A/F sensor (bank 1, sensor 1) VLBLB1 line short to ground
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.