Advanced Diagnostics

Advanced Diagnostics-DTC P0137: Secondary Heated Oxygen Sensor (Secondary HO2S (Sensor 2)) Circuit Low Voltage

General Description






The secondary heated oxygen sensor (secondary HO2S (sensor 2)) detects the oxygen content in the exhaust gas downstream of the three way catalytic converter (TWC) during stoichiometric air/fuel ratio feedback control. The powertrain control module (PCM) controls the air/fuel ratio from the air/fuel ratio (A/F) sensor (sensor 1) output voltage to optimize the TWC efficiency. After current is applied to the secondary HO2S heater, if the secondary HO2S output continues to be low (lean) during feedback control, the PCM detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type, OBD Status






Enable Conditions






Malfunction Threshold
The secondary HO2S (sensor 2) output voltage [HO2S S2 OUTPUT VOLTAGE] is 0.12 V or less for at least 5 seconds.

[ ]: HDS Parameter

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.

- Secondary HO2S (sensor 2) SO2 line short to ground
- Secondary HO2S (sensor 2) SO2SG line short to ground
- PCM internal circuit failure

Confirmation Procedure

With the HDS
None.

With the Driving Pattern
Start the engine. Hold the engine speed at 3,000 rpm without load (in P or N) until the radiator fan comes on, then let it idle.

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.