P0140 on BMW: Causes, Symptoms and Fix Cost
Quick Answer
Safe to drive (short-term)
P0140 on a BMW means the ECU cannot detect any activity from the downstream oxygen sensor on Bank 1 (post-catalyst, Sensor 2). The sensor voltage is either flatlined or out of range. This usually points to a failed sensor, an open circuit in the wiring, or a connector that has come loose or corroded.
- Severity
- Moderate · Emissions
- Typical repair cost, all makes
- €1-€310
Connect a standard OBD2 adapter (Bluetooth LE on iPhone) to your BMW and Skanyx tells you what P0140 means on that engine, whether it is safe to keep driving, and what the fix should cost. Free on iPhone and Android.
Get Skanyx freeWhat does P0140 mean on a BMW?
The Quick Answer above is the generic definition. What follows is the model-specific detail for the BMW models that log P0140.
BMW 3 Series
2006-2024
On the N52 and N55 the downstream sensor connector clip becomes brittle with age and can break. A broken clip lets the connector vibrate loose, which presents as P0140 (no activity) even though the sensor itself is fine. Inspect and re-secure the connector before condemning the sensor. On the N52 there are two downstream sensors, and P0140 is the bank 1 one (cylinders 1-3).
Source: bimmerworld.com
Sources
- bimmerworld.com bimmerworld.com/Exhaust/O2-Sensors/BMW-Engine-Oxygen-Sensor-O2-11787545074.html
What causes P0140 on a BMW?
Beyond the generic causes listed on the main P0140 page, these are the patterns noted for BMW models:
Broken connector clip on N52/N55 causing intermittent disconnection
: BMW 3 Series
Heater element burnout on high-mileage cars producing a flat signal
: BMW 3 Series
How to diagnose P0140 on a BMW with OBD2
- Read freeze frame data and check for a heater code for the same sensor (P0141), which points to a power or heater problem at the sensor. Several heater codes at once (for example P0135 and P0141) point to a shared fuse or supply
- Inspect the Bank 1 Sensor 2 connector visually for disconnection, corrosion, water intrusion, or melted plastic
- Use a multimeter at the sensor connector to verify ground, heater power (battery voltage with key on), and signal continuity back to the ECU
- If wiring tests good, unplug the sensor and measure heater resistance directly. Healthy: 2-15 ohms. Open: burned-out heater. The sensor needs replacement
- If a new sensor still shows no activity, scope the signal wire for opens or shorts between the sensor and ECU
How much does P0140 cost to fix on a BMW? (EUR)
Estimated repair costs for P0140 in EUR, compiled across makes. Expect BMW parts and labour towards the upper end of each range.
| Repair | Parts Cost | Labor Cost | Total Estimate | DIY Difficulty |
|---|---|---|---|---|
| Replace downstream O2 sensor (Bank 1, Sensor 2) | €40–€180 | €50–€130 | €90–€310 | Moderate |
| Repair O2 sensor wiring or connector | €5–€25 | €40–€120 | €45–€145 | Moderate |
| Replace heater fuse and diagnose underlying short | €1–€10 | €0–€80 | €1–€90 | Easy |
Prices estimated as of October 2026. Costs vary by region, vehicle, and shop.
Codes related to P0140
These codes are often seen alongside P0140 or point to related issues, on any make:
Looking for the full P0140 reference (all makes, full diagnosis flow, complete repair cost matrix)? See the main P0140 guide