DTC Advanced Diagnostics: P0138 (3.0L Engine)
DTC P0138: Secondary Heated Oxygen Sensor (Secondary HO2S (Sensor 2)) Circuit High Voltage
General Description
The secondary heated oxygen sensor (secondary HO2S (sensor 2)) detects the oxygen density in the exhaust gas and converts it into electrical signals. If the secondary HO2S (sensor 2) output voltage is a specified value for a set time, the powertrain control module (PCM) detects a malfunction and stores a DTC.
Monitor Execution, Sequence, Duration, DTC Type
| Execution | Continuous |
| Sequence | None |
| Duration | 1.0 second or more |
| DTC Type | Two drive cycles, MIL on |
Enable Conditions
| Condition | Minimum | Maximum |
|---|---|---|
| 12 volt battery voltage [Battery]* | 10.0 V | - |
| State of the engine | Running | |
*: Maintain for 2.5 seconds or more[ ]: HDS Parameter
Malfunction Threshold
Either of the condition continues for at least 1.0 second:
- The SO2 terminal voltage or SO2SG terminal voltage is 4.779 V or more.* 1, * 2
- The voltage between the SO2 terminal and the SO2SG terminal is 1.2 V or more.* 1
*1: USA and Canada models*2: Mexico models
Possible Cause
- Secondary HO2S (sensor 2) SO2 line short to power
- Secondary HO2S (sensor 2) SO2SG line short to power
- Secondary HO2S (sensor 2) failure
- 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.