DTC Advanced Diagnostics: P0159 (3.5L Engine) (2025)
DTC P0159 : Front Secondary Heated Oxygen Sensor (Secondary HO2S (Bank 2, Sensor 2)) Slow Response
General Description
The front secondary heated oxygen sensor (secondary HO2S (bank 2, sensor 2)) detects the oxygen content in the exhaust gas downstream of the front warm up three way catalytic converter (WU-TWC) (bank 2) during stoichiometric air/fuel ratio feedback control. The powertrain control module (PCM) controls the air/fuel ratio with the front air/fuel ratio (A/F) sensor (bank 2, sensor 1) output voltage to optimize the front WU-TWC (bank 2)'s efficiency. When the front secondary HO2S (bank 2, sensor 2) does not change during lean air/fuel ratio when the throttle is closed, after full current is applied to the front secondary HO2S (bank 2, sensor 2) heater, and output remains within the specified range continuously, the PCM detects a malfunction and stores a DTC.
Monitor Execution, Sequence, Duration, DTC Type
| Execution | Once per driving cycle |
| Sequence | P0158 is judged as OK |
| Duration | 8.0 seconds or more |
| DTC Type | Two drive cycles, MIL on |
Enable Conditions
| Condition | Minimum | Maximum |
|---|---|---|
| Elapsed time after starting the engine | 2 minutes | - |
| Engine coolant temperature [ECT Sensor 1] | 155.9 deg.F (68.8 deg.C) | - |
| Intake air temperature [IAT Sensor (1)] | -13 deg.F (-25 deg.C) | - |
| Estimated catalyst temperature* 1 [Catalyst Temp B2] | 842 deg.F (450 deg.C) | - |
| Engine speed [Engine Speed] | - | 4, 000 RPM |
| Secondary HO2S output voltage [HO2S B2 S2] | 0.05 V | - |
| Intake air amount | 2 g/s (0.07 oz/s) | - |
| Fuel feedback | During deceleration | |
*1: USA and Canada models
[ ]: HDS Parameter
Malfunction Threshold
The front secondary HO2S (bank 2, sensor 2) output voltage [HO2S B2 S2] is 0.05 V or more for at least 8.0 seconds.
Possible Cause
The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
- Front secondary HO2S (bank 2, sensor 2) responsive deterioration
- Exhaust system failure (exhaust gas leak)
Confirmation Procedure
Operating Condition
- Start the engine. Hold the engine speed [Engine Speed] at 3, 000 RPM without load (in P or N) until the radiator fan comes on.
- Drive the vehicle at a steady speed between 55 - 75 mph (90 - 120 km/h) for at least 1 minute.
- Decelerate with the throttle valve fully closed for at least 8 seconds.
- Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.
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.