P0140 on a 2017 Honda Civic
Post-Cat O2 Sensor No Activity (Bank 1 Downstream)
P0140 on a 2017 Honda Civic indicates post-cat o2 sensor no activity (bank 1 downstream). It usually stays drivable short-term but should be diagnosed promptly. The most common cause is open circuit in the o2 signal or ground wire (typically $80–$350). Confirm the root cause before replacing parts.
What does P0140 mean on a 2017 Honda Civic?
P0140 is set when the Bank 1 downstream oxygen sensor shows no meaningful activity at all. The voltage sits flat — typically parked at the ECM's bias voltage of roughly 0.4–0.5 V — and never moves, even under conditions that should force it to move. Bank 1 is the bank containing cylinder number 1, and Sensor 2 is the sensor after the catalytic converter. P0140 is different from a sensor reading too low (P0137) or too high (P0138): with no activity the ECM is effectively looking at an open circuit or a completely dead sensor element.
The symptoms, causes, and diagnostic steps below describe P0140 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 P0140?
In most cases a 2017 Honda Civic stays drivable for short trips with P0140 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 P0140 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
- Frequently sets alongside P0141 when the sensor heater has failed
What causes P0140 on a 2017 Honda Civic?
| Cause | Likelihood | Estimated repair (USD) |
|---|---|---|
| Open circuit in the O2 signal or ground wire | Most common | $80–$350 |
| Failed Bank 1 downstream O2 sensor (dead element) | Most common | $150–$450 |
| Failed sensor heater leaving the sensor below operating temperature A zirconia sensor produces no signal until it is hot — a dead heater looks exactly like a dead sensor. | Common | $150–$450 |
| Blown O2 heater fuse | Common | $5–$30 |
| Corroded or disconnected downstream O2 sensor connector | Common | $30–$200 |
| Harness chafed or melted against the exhaust | Common | $80–$350 |
| Failed PCM input for the downstream sensor 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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Pull every O2 code before deciding anything
P0140 next to P0141 tells a very different story from P0140 alone. With P0141 the heater circuit has failed and the sensor never gets hot enough to produce a signal — the heater is the fault and the "no activity" is a consequence. P0140 by itself points at the signal circuit or the sensor element.
Tools: Scan tool with full code retrieval
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Check the O2 heater fuse
Many vehicles run all O2 heaters from one fuse; some split them by bank. Test the correct fuse with a test light rather than eyeballing it. If a fresh fuse blows straight away, there is a short in the harness or inside a sensor, and that short is your actual repair.
Tools: Test light or multimeter, Replacement fuse
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Measure heater resistance at the sensor
Unplug the downstream sensor and measure across the heater terminals — typically somewhere in the 3 to 15 Ω range depending on the sensor. Infinite resistance means the heater element is open, the sensor never warms up, and it will never produce a signal no matter how good the wiring is.
Tools: Multimeter, Wiring diagram
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Verify bias voltage reaches the connector
With the sensor unplugged and the key on, the scan tool should still show the ECM's bias voltage on the signal PID. If it does, the signal wire is intact back to the PCM and the sensor is the suspect. If the reading goes to zero or reads erratically, the fault is in the harness.
Tools: Scan tool, Multimeter
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Force the sensor to respond and watch for movement
With the engine fully warm, briefly create a rich condition — most easily by snapping the throttle — and watch the downstream PID. Even a lazy but living sensor will show some movement. A trace that never leaves its resting value under any condition confirms the element is dead.
Tools: Scan tool with graphing PIDs
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 P0140 on a 2017 Honda Civic?
- Replace the Bank 1 downstream O2 sensor with an OEM part
- Repair the open O2 signal or ground circuit
- Replace the blown O2 heater fuse
- Repair harness chafed or melted against the exhaust
- Clean or replace the corroded downstream sensor connector
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 P0140 is most likely to originate, so confirm your engine before ordering parts.
Engine data: EPA fueleconomy.gov.
The four Bank 1 Sensor 2 codes, side by side
All four describe the same downstream sensor. Reading them together narrows the diagnosis far more than any one of them alone:
| Code | What the ECM saw |
|---|---|
| P0136 | Generic circuit fault that fits no narrower pattern |
| P0137 | Voltage below the calibrated minimum |
| P0138 | Voltage above the calibrated maximum |
| P0140 | No activity at all — the signal never moves |
P0140 is the “flatline” member of the family. Where P0137 and P0138 mean the sensor is saying something wrong, P0140 means it is saying nothing.
Check the heater before condemning the sensor element
A zirconia oxygen sensor generates no usable signal until it reaches roughly 350 °C. That is why every modern sensor has a heater built into it. When the heater dies, the sensor sits cold, produces nothing, and the ECM logs exactly what it observes: no activity. The sensor element itself may be in perfect condition.
This matters because the two faults often present together. If you have P0140 and P0141 on the same scan, the heater circuit is the thing to diagnose. Sometimes that is a five-dollar fuse rather than a sensor.
The bias-voltage test
Every downstream O2 circuit is held at a reference bias voltage by the ECM, usually around 0.4–0.5 V, so that the ECM can tell the difference between “sensor is reading mid-range” and “wire is broken.” Unplug the sensor, key on, and watch the PID:
- Bias voltage present → the wiring from connector to PCM is intact. The sensor is the suspect.
- Reading drops to zero or jumps around → the circuit is broken or shorted. Chase the harness; do not buy a sensor yet.
Living with P0140
The downstream sensor watches the catalyst; it does not run the engine. So the car will drive normally, and this is not a code that will leave you stranded. What it will do is block the catalyst readiness monitor from completing, which fails an emissions test even after the light is cleared. Fix it before your inspection is due, not the week of.
P0140 on a 2017 Honda Civic: frequently asked questions
What does diagnostic trouble code P0140 mean on a 2017 Honda Civic?
P0140 is set when the Bank 1 downstream oxygen sensor shows no meaningful activity at all. The voltage sits flat — typically parked at the ECM's bias voltage of roughly 0.4–0.5 V — and never moves, even under conditions that should force it to move. Bank 1 is the bank containing cylinder number 1, and Sensor 2 is the sensor after the catalytic converter. P0140 is different from a sensor reading too low (P0137) or too high (P0138): with no activity the ECM is effectively looking at an open circuit or a completely dead sensor element.
What are the symptoms of P0140 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. Frequently sets alongside P0141 when the sensor heater has failed
What causes P0140 on a 2017 Honda Civic?
Open circuit in the O2 signal or ground wire (most-common). Failed Bank 1 downstream O2 sensor (dead element) (most-common). Failed sensor heater leaving the sensor below operating temperature (common). Blown O2 heater fuse (common). Corroded or disconnected downstream O2 sensor connector (common). Harness chafed or melted against the exhaust (common). Failed PCM input for the downstream sensor circuit (rare)
Is it safe to drive a 2017 Honda Civic with P0140?
In most cases a 2017 Honda Civic stays drivable for short trips with P0140 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.