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 Troubleshooting: P0139, P0159 (2013-15)
DTC P0139 : Rear Secondary HO2S (Bank 1, Sensor 2) Slow Response DTC P0159 : Front Secondary HO2S (Bank 2, Sensor 2) Slow Response
- Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information - Refer to: How to Troubleshoot the Fuel and Emissions Systems (2013-15), or How to Troubleshoot the A/T System (2013-15) .
- 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.
- Information marked with an asterisk (*) applies to the front bank (Bank 2).
| DTC Description | Confirmed DTC | Pending DTC | Freeze Frame |
|---|---|---|---|
| P0139 Rear Secondary HO2S (Bank 1, Sensor 2) Slow Response | |||
| P0159 Front Secondary HO2S (Bank 2, Sensor 2) Slow Response |
DTC (PGM-FI)
- Problem verification:
Press the engine start/stop button to select the ON mode.
- 2. Clear the DTC with the HDS - Refer to: How to Troubleshoot the Fuel and Emissions Systems (2013-15), or How to Troubleshoot the A/T System (2013-15) .
Clear DTC
- 3. 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.
- 4. Test-drive under these conditions:
- Engine coolant temperature (ECT SENSOR 1) above 158 °F (70 °C)
- Transmission in D
- 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 and/or P0159* in the DTCs MENU with the HDS.
DTC Description OBD STATUS P0139 Rear Secondary HO2S (Bank 1, Sensor 2) Slow Response P0159 Front Secondary HO2S (Bank 2, Sensor 2) Slow Response Does the HDS indicate FAILED?
YES
The failure is duplicated. Replace secondary HO2S (Sensor 2) , then do the repair verification.
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 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.
- Repair verification (OBD STATUS check):
- 1. Press the engine start/stop button to select the ON mode.
- 2. Reset the PCM with the HDS - Refer to: How to Troubleshoot the Fuel and Emissions Systems (2013-15), or How to Troubleshoot the A/T System (2013-15) .
Reset PCM
- 3. Do the PCM idle learn procedure.
- 4. 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.
- 5. Test-drive under these conditions:
- Engine coolant temperature (ECT SENSOR 1) above 158 °F (70 °C)
- Transmission in D
- 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 - 6. Monitor the OBD STATUS for DTC P0139 and/or P0159* in the DTCs MENU with the HDS.
DTC Description OBD STATUS P0139 Rear Secondary HO2S (Bank 1, Sensor 2) Slow Response P0159 Front Secondary HO2S (Bank 2, Sensor 2) Slow Response DTC (PGM-FI)
Does the HDS indicate PASSED, FAILED, EXECUTING, or OUT OF CONDITION?
PASSED (P0139)
Troubleshooting is complete. If any other Pending or Confirmed DTCs were indicated, go to the indicated DTC's troubleshooting.
PASSED (P0159)
Troubleshooting is complete. If any other Pending or Confirmed DTCs were indicated, go to the indicated DTC's troubleshooting.
FAILED (P0139)
Go to step 1 and recheck.
FAILED (P0159)
Go to step 1 and recheck.
EXECUTING
Keep the test condition until a result comes on.
OUT OF CONDITION
Meet the test condition, and check the OBD STATUS again.
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.