DTC Advanced Diagnostics: P0037 (3.0L Engine)
DTC P0037: Secondary Heated Oxygen Sensor (Secondary HO2S (Sensor 2)) Heater Circuit Low Voltage
General Description
The secondary heated oxygen sensor (secondary HO2S (sensor 2)) heater is controlled by the duty signal command from the powertrain control module (PCM) to heat the secondary HO2S (sensor 2) to an optimal temperature. The output driver circuit in the PCM monitors the voltage level of the SO2HT terminal, and if the voltage level of the SO2HT terminal is ON (low voltage) despite the PCM outputs OFF signal to the secondary HO2S (sensor 2), 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 | - |
| Secondary HO2S (sensor 2) heater output duty | - | 99.9 % |
| State of the engine | Running | |
[ ]: HDS Parameter
Malfunction Threshold
The voltage level of the SO2HT terminal is ON (low voltage) for at least 5 seconds despite the PCM outputs OFF signal to the secondary HO2S (sensor 2).
Possible Cause
- Secondary HO2S (sensor 2) SO2HT line short to ground
- Secondary HO2S (sensor 2) SO2HT line open
- Secondary HO2S (sensor 2) heater power supply line 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.