P0156 on a 2017 Honda Civic
Post-Cat O2 Sensor Circuit Fault (Bank 2)
P0156 on a 2017 Honda Civic indicates post-cat o2 sensor circuit fault (bank 2). It usually stays drivable short-term but should be diagnosed promptly. The most common cause is failed bank 2 downstream o2 sensor (typically $150–$450). Confirm the root cause before replacing parts.
What does P0156 mean on a 2017 Honda Civic?
P0156 is the Bank 2 counterpart of P0136. The ECM has detected a general circuit fault on the Bank 2 downstream oxygen sensor — the one after the catalytic converter on the cylinder bank that does NOT contain cylinder number 1. It is the catch-all code: it covers wiring faults, intermittent connections, and readings that fall outside expectations in a way that does not fit the narrower codes P0157 (low voltage), P0158 (high voltage), or P0160 (no activity). Because Bank 2 only exists on engines with two cylinder banks, P0156 applies to V6, V8, V10, V12, and flat / boxer engines only.
The symptoms, causes, and diagnostic steps below describe P0156 itself, so they read the same on nearby Honda Civic model years. Powertrain and trim details vary year to year — confirm the specifics against your own vehicle before buying parts.
Is it safe to drive a 2017 Honda Civic with P0156?
In most cases a 2017 Honda Civic stays drivable for short trips with P0156 active, but diagnose and repair it promptly. This is a moderate-severity code — ignoring it can lead to further damage or a failed emissions test.
What are the symptoms of P0156 on a 2017 Honda Civic?
- Check Engine Light is illuminated
- Catalyst readiness monitor will not complete
- Often no drivability symptoms at all
- Possible slight reduction in fuel economy
- Vehicle will fail emissions / smog testing
What causes P0156 on a 2017 Honda Civic?
| Cause | Likelihood | Estimated repair (USD) |
|---|---|---|
| Failed Bank 2 downstream O2 sensor | Most common | $150–$450 |
| Damaged sensor wiring chafed or melted against the exhaust | Common | $80–$350 |
| Corroded Bank 2 downstream O2 sensor connector | Common | $30–$200 |
| Exhaust leak upstream of the Bank 2 downstream sensor | Occasional | $100–$500 |
| Damaged or crushed sensor pigtail from a previous repair | Occasional | $80–$300 |
| Failed PCM input for the Bank 2 downstream circuit | Rare | $400–$1,500 |
Cost ranges are editorial estimates for parts and labor at an independent U.S. shop — not quotes. What you actually pay moves with your region, the shop's hourly rate, which engine you have, and how much diagnostic time the job takes. Dealer service departments typically sit above these ranges.
How to diagnose this on a 2017 Honda Civic
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Establish which bank is Bank 2 on this engine
Bank 2 is the cylinder bank without cylinder number 1. There is no universal rule for which physical side that is — it depends on the engine's cylinder numbering, which the manufacturer defines. Look it up in service information before you crawl under the car. Replacing the Bank 1 sensor because it was easier to reach is a genuinely common and completely wasted repair.
Tools: Vehicle-specific service information, Vehicle lift or jack stands
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Read every O2 code to narrow the picture
P0156 on its own is deliberately vague. Alongside P0157 it points at low voltage specifically; with P0158 at high voltage; with P0160 at no activity; with P0161 at the heater circuit. The combination tells you whether to target the wiring, the sensor element, or the heater.
Tools: Scan tool with full code retrieval
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Inspect the Bank 2 sensor wiring and connector
Trace the harness from the sensor body back to the chassis connector. Look for insulation melted by exhaust contact, chafing against the underbody or suspension, and rodent damage. Open the connector and check for water intrusion and green corrosion — downstream connectors sit in road spray and take a beating in salt-belt winters.
Tools: Flashlight, Inspection mirror, Electrical contact cleaner
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Graph the Bank 2 signal against Bank 1
With the engine warm and held at 2500 RPM, watch both downstream sensors together. A healthy post-cat sensor sits relatively steady around 0.6–0.8 V. Having the Bank 1 sensor on the same graph gives you a known-good reference on the same engine at the same moment — if Bank 2 is flat, erratic, or stuck while Bank 1 behaves, you have confirmed the fault.
Tools: Scan tool with multi-PID graphing
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Verify bias voltage at the connector
Unplug the Bank 2 downstream sensor and turn the key on. The scan tool should still show the ECM's bias voltage, typically around 0.4–0.5 V. If it does not, the fault lies between the connector and the PCM rather than in the sensor.
Tools: Scan tool, Multimeter
Known Technical Service Bulletins for the 2015-2019 Honda Civic
Manufacturers publish Technical Service Bulletins (TSBs) when a known issue affects a specific vehicle. These bulletins come from the NHTSA database for your Honda Civic.
- ENGINE Jul 28, 2025
Service Bulletin - Oil leak at timing chain tensioner inspection cover due to possible insufficient sealant adhesion on inspection cover.
NHTSA #11021745 - FUEL/PROPULSION SYSTEM Aug 6, 2024
Dealer Message - American Honda Motor Co., Inc. (AHM) is searching for certain 2018-2020 Accords, 2016-2020 Civics, 2017-2020 CR-Vs, & 2018-2020 Odysseys that have been diagnosed to be in need of the low-pressure fuel pump, fuel strainer, fuel meter or fuel tank replacement.
NHTSA #11006249 - FUEL/PROPULSION SYSTEM Jul 22, 2024
Dealer Message - American Honda Motor Co., Inc. (AHM) is searching for certain 2018-2020 Accords, 2016-2020 Civics, 2017-2020 CR-Vs, & 2018-2020 Odysseys that have been diagnosed to be in need of the low-pressure fuel pump, fuel strainer, fuel meter or fuel tank replacement. If you have a vehicle that match the qualifiers listed below, AHM requests to have the photos of the lock ring & the low-pressure fuel pump flange taken & sent to TIS (click HERE for example photos).
NHTSA #11005271 - FUEL/PROPULSION SYSTEM Jul 6, 2024
Dealer Message - Dealer Message - American Honda Motor Co., Inc. (AHM) is searching for certain 2018-2020 Accords, 2016-2020 Civics, 2017-2020 CR-Vs, & 2018-2020 Odysseys that have been diagnosed to be in need of the low-pressure fuel pump, fuel strainer, fuel meter or fuel tank replacement.
NHTSA #11004264 - VISIBILITY/WIPER Jun 19, 2024
Service Bulletin - Due to a new North America regulation which introduces a new refrigerant and oil requirement, the compressor shaft seal may leak. American Honda is extending the warranty on the A/C compressor shaft seal from the original 3 years to 10 years from the original date of purchase, with no mileage limitation. The new refrigerant and oil may cause swelling of the compressor shaft seal. The swelling may lead to abnormal wearing of the seal which may increase seal gaps around the compressor shaft allowing refrigerant to leak out.
NHTSA #11002711 - VISIBILITY/WIPER Jun 19, 2024
Service Bulletin - American Honda is extending the warranty on the A/C condenser to 10 years from the original date of purchase with unlimited miles. This warranty extension only covers vehicles that have a defective A/C condenser from the factory. The A/C condenser was not manufactured to specification. As a result, corrosion may develop in the form of tiny holes in the condenser tube walls that allow the refrigerant to leak out.
NHTSA #11002705
+14 more TSBs available in MECH AI's TSB explorer for this vehicle.
NHTSA complaints & recalls for the 2017 Honda Civic
Owner-reported safety complaints and official recalls filed with the U.S. National Highway Traffic Safety Administration for the 2017 Honda Civic. Use these to gauge how common a problem is on your specific vehicle before you start chasing Honda Civic diagnostics.
- ENGINE 65
- STEERING 161
- UNKNOWN OR OTHER 160
- ELECTRICAL SYSTEM 99
- SERVICE BRAKES 35
6 active recalls
- STEERING:ELECTRIC POWER ASSIST SYSTEM Sep 2018
Honda (American Honda Motor Co.) is recalling certain 2017-2018 Honda Civic and CR-V vehicles. The magnet that controls the torque sensor output signal for the electronic power steering system may not be properly secured, allowing the magnet to become dislodged. During a full…
NHTSA campaign 18V663000 - EQUIPMENT:OTHER:OWNERS/SERVICE/OTHER MANUAL Nov 2018
Honda (American Honda Motor Co.) is recalling certain 2017-2018 Honda Civic Hatchback and Civic Type R vehicles. The owners guide in these vehicles may not have been included or if included, the owner's guide may not have been properly provided required information. As such, t…
NHTSA campaign 18V817000 - AIR BAGS Apr 2018
Honda (American Honda Motor Co.) is recalling certain 2017 Honda Civic Hatchback and Civic Type R vehicles. Driver and front passenger seatback pads sold as replacement service parts were made without slit openings for the seat-mounted side air bags. In the event of a crash nece…
NHTSA campaign 18V266000 - POWER TRAIN:DRIVELINE:DRIVESHAFT Nov 2017
Honda (American Honda Motor Co.) is recalling certain 2017 Honda Civic Sedan and Coupe vehicles. The right halfshaft may have been improperly heat treated, reducing its strength.…
NHTSA campaign 17V706000
How do I fix P0156 on a 2017 Honda Civic?
- Replace the Bank 2 downstream O2 sensor with an OEM part
- Repair damaged Bank 2 downstream sensor wiring
- Clean or replace the corroded sensor connector
- Repair exhaust leaks upstream of the Bank 2 downstream sensor
Engines in the 2017 Honda Civic
The 2017 Honda Civic was offered with the 1.5L 4-cylinder and 2.0L 4-cylinder engines. Which one you have changes where P0156 is most likely to originate, so confirm your engine before ordering parts.
Engine data: EPA fueleconomy.gov.
Bank 2 only exists on two-bank engines
P0156 refers to the downstream sensor on the bank that does not contain cylinder number 1. Inline engines — inline-3, inline-4, inline-5, inline-6 — have a single bank and no Bank 2 sensors at all. If a generic scan tool shows P0156 on a four-cylinder, treat the description with suspicion: either the tool’s lookup table is generic, or the manufacturer has assigned a different meaning to that number. Check the OEM definition before buying parts.
The Bank 2 codes mirror the Bank 1 codes exactly
If you have worked on the Bank 1 sensor before, the same diagnosis applies one bank over:
| Bank 1 | Bank 2 | Meaning |
|---|---|---|
| P0136 | P0156 | Generic circuit fault (catch-all) |
| P0137 | P0157 | Voltage too low |
| P0138 | P0158 | Voltage too high |
| P0140 | P0160 | No activity detected |
| P0141 | P0161 | Heater circuit fault |
The parts, the tests, and the failure modes are identical. Only the location on the vehicle changes.
Use Bank 1 as your reference
The single biggest advantage of diagnosing a Bank 2 sensor is that the vehicle carries a matched known-good sensor on the other bank. Graph both at once. Two sensors of the same age, on the same engine, under the same load should behave the same way. When one does not, you are done guessing.
What the downstream sensor actually does
It monitors catalyst efficiency by comparing what comes out of the catalyst to what the upstream sensor saw going in. It contributes only a slow secondary trim correction to fuelling — the upstream sensor does the real fuel control work. That is why P0156 shows up as a warning light and an emissions failure rather than as a car that runs badly, and why there is no need to panic about driving it. It still needs fixing before an inspection, because the catalyst monitor cannot complete while the fault is present.
P0156 on a 2017 Honda Civic: frequently asked questions
What does diagnostic trouble code P0156 mean on a 2017 Honda Civic?
P0156 is the Bank 2 counterpart of P0136. The ECM has detected a general circuit fault on the Bank 2 downstream oxygen sensor — the one after the catalytic converter on the cylinder bank that does NOT contain cylinder number 1. It is the catch-all code: it covers wiring faults, intermittent connections, and readings that fall outside expectations in a way that does not fit the narrower codes P0157 (low voltage), P0158 (high voltage), or P0160 (no activity). Because Bank 2 only exists on engines with two cylinder banks, P0156 applies to V6, V8, V10, V12, and flat / boxer engines only.
What are the symptoms of P0156 on a 2017 Honda Civic?
Check Engine Light is illuminated. Catalyst readiness monitor will not complete. Often no drivability symptoms at all. Possible slight reduction in fuel economy. Vehicle will fail emissions / smog testing
What causes P0156 on a 2017 Honda Civic?
Failed Bank 2 downstream O2 sensor (most-common). Damaged sensor wiring chafed or melted against the exhaust (common). Corroded Bank 2 downstream O2 sensor connector (common). Exhaust leak upstream of the Bank 2 downstream sensor (occasional). Damaged or crushed sensor pigtail from a previous repair (occasional). Failed PCM input for the Bank 2 downstream circuit (rare)
Is it safe to drive a 2017 Honda Civic with P0156?
In most cases a 2017 Honda Civic stays drivable for short trips with P0156 active, but it should be diagnosed and repaired promptly — this is a moderate-severity code. Ignoring it can lead to further damage or a failed emissions test.