P0140 on a 2017 Ram 1500
Post-Cat O2 Sensor No Activity (Bank 1 Downstream)
P0140 on a 2017 Ram 1500 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 Ram 1500?
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 Ram 1500 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 Ram 1500 with P0140?
In most cases a 2017 Ram 1500 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 Ram 1500?
- 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 Ram 1500?
| 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 Ram 1500
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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
NHTSA complaints & recalls for the 2017 Ram 1500
Owner-reported safety complaints and official recalls filed with the U.S. National Highway Traffic Safety Administration for the 2017 Ram 1500. Use these to gauge how common a problem is on your specific vehicle before you start chasing Ram 1500 diagnostics.
- ENGINE 154
- POWER TRAIN 97
- STEERING 215
- ELECTRICAL SYSTEM 102
- SERVICE BRAKES 91
13 active recalls
- ENGINE AND ENGINE COOLING:ENGINE:DIESEL Aug 2020
Chrysler (FCA US LLC) is recalling certain 2014-2018 Ram 1500 and 2014-2016 Jeep Grand Cherokee vehicles equipped with 3.0L diesel engines. The crankshaft position sensor tone wheel may delaminate causing the engine to lose its ability to synchronize the fuel injector pulses and…
NHTSA campaign 20V475000 - LATCHES/LOCKS/LINKAGES:TAILGATE:LATCH May 2019
Chrysler (FCA US LLC) is recalling certain 2015-2017 Ram 1500, 2500 and 3500 pickup trucks equipped with an 8 foot bed and a power locking tailgate. Chrysler is also recalling all 2013-2014 and 2018 Ram 1500, 2500 and 3500 pickup trucks built before April 1, 2018 with a 6 or 8 f…
NHTSA campaign 19V347000 - STRUCTURE:BODY:TAILGATE Jul 2018
Chrysler (FCA US LLC) is recalling certain 2015-2017 RAM 1500, 2500, and 3500 pickup trucks equipped with a power locking tailgate and either a 5 foot, 7 inch or 6 foot, 4 inch bed. The tailgate actuator limiter tab may fracture and cause the tailgate to unlatch and open while d…
NHTSA campaign 18V486000 - ELECTRICAL SYSTEM:WIRING May 2018
Chrysler (FCA US LLC) is recalling certain 2014-2018 Dodge Journey, Charger and Durango, RAM 2500, 3500, 3500 Cab Chassis (more than 10,000lb), 4500 Cab Chassis and 5500 Cab Chassis, Jeep Cherokee and Grand Cherokee and Chrysler 300, 2014-2019 RAM 1500, 2015-2018 Dodge Challenger…
NHTSA campaign 18V332000
How do I fix P0140 on a 2017 Ram 1500?
- 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 Ram 1500
The 2017 Ram 1500 was offered with the 3.0L 6-cylinder, 3.6L 6-cylinder and 5.7L 8-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 Ram 1500: frequently asked questions
What does diagnostic trouble code P0140 mean on a 2017 Ram 1500?
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 Ram 1500?
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 Ram 1500?
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 Ram 1500 with P0140?
In most cases a 2017 Ram 1500 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.