DTC Advanced Diagnostics: P0031 (3.0L Engine)
DTC P0031: Rear Air/Fuel Ratio (A/F) Sensor (Bank 1, Sensor 1) Heater Circuit Low Voltage
General Description
The rear air/fuel ratio (A/F) sensor (bank 1, sensor 1) heater is controlled by the duty signal command from the powertrain control module (PCM) to heat the rear A/F sensor (bank 1, sensor 1) to an optimal temperature. The monitor circuit in the PCM monitors the voltage level of the AFHTB1 terminal, and if an abnormality of the terminal voltage is detected, the PCM detects a malfunction and stores a DTC.
Monitor Execution, Sequence, Duration, DTC Type
| Execution | Continuous |
| Sequence | None |
| Duration | 5 seconds or more |
| DTC Type | Two drive cycles, MIL on |
Enable Conditions
| Condition | Minimum | Maximum |
|---|---|---|
| 12 volt battery voltage [Battery] | 10.0 V | - |
| A/F sensor (sensor 1) heater output duty | - | 99.9 % |
| Vehicle | ON mode | |
[ ]: HDS Parameter
Malfunction Threshold
The monitor circuit in the PCM cannot detect the pulse edge for at least 5 seconds while the rear A/F sensor (bank 1, sensor 1) heater is duty controlled at 99.9 % or less.
Possible Cause
- Rear A/F sensor (bank 1, sensor 1) AFHTB1 line short to ground
- Rear A/F sensor (bank 1, sensor 1) AFHTB1 line open
- Power distribution module stuck off
- 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, the freeze data, and the on-board snapshot 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, the freeze data, and the on-board snapshot can be cleared with the scan tool clear command.