Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC P0139
DTC P0139 : Secondary HO2S (Sensor 2) Slow Response
NOTE:
- Before you troubleshoot, review the general troubleshooting information .
- If the exhaust leaks from the exhaust system, this DTC will be set. Check for damage in the exhaust pipe and repair it if needed.
| DTC Description | Confirmed DTC | Pending DTC | Freeze Frame |
|---|---|---|---|
| P0139 Secondary HO2S (Sensor 2) Slow Response |
DTC (PGM-FI)
- Problem verification
-1. Turn the vehicle to the ON mode.
-2. Clear the DTC with the HDS.
-3. Start the engine. Hold the engine speed at 3, 000 rpm without load (CVT in P or N, M/T in neutral) until the radiator fan comes on, then let it idle.
-4. Test-drive under these conditions:
- Engine coolant temperature (ECT SENSOR 1) above 158 deg. F (70 deg. C)
- CVT in D, M/T in 5th
- Drive at a steady speed between 55-75 mph (90-120 km/h) for 1 minute, then decelerate (with the throttle fully closed) for 10 seconds
Signal Current conditions Values Unit ECT SENSOR 1 VEHICLE SPEED -5. Monitor the OBD STATUS for DTC P0139 in the DTCs MENU with the HDS.
DTC Description OBD STATUS P0139 Secondary HO2S (Sensor 2) Slow Response Does the HDS indicate FAILED?
YES
The failure is duplicated. Replace secondary HO2S (Sensor 2) .
NO
If the HDS indicates PASSED, intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at secondary HO2S (Sensor 2) and the PCM. If the freeze data/on-board snapshot of this DTC is recorded, try to reproduce the failure under the same conditions with the freeze data/on-board snapshot . If the HDS indicates EXECUTING, keep driving until a result comes on. If the HDS indicates OUT OF CONDITION, go to step 1-3 on this step and recheck.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.