P0152
PowertrainO2 Sensor Circuit High Voltage (Bank 2 Sensor 1)
Most drivers won't notice much beyond the engine light coming on, and maybe a slightly thirstier car on the weekly fuel bill. Behind the scenes, the front oxygen sensor on bank 2 (the cylinder bank that doesn't have cylinder number one) is telling the ECU its voltage is sitting too high. That signal normally swings up and down quickly between roughly 0.1V and 0.9V as the mixture changes. When it pegs high and stays there, the ECU stops trusting it and logs P0152. This is mainly a V6 and V8 issue, since you only get a bank 2 on engines with two cylinder banks.
ⓘ Information only. This page provides general educational information about fault code P0152. We do not assess the urgency or safety implications of any specific fault. That requires in-person diagnosis by a qualified mechanic. Full terms.
Recommended next steps
Whether a fault is urgent, drivable, or routine depends entirely on the cause on a specific vehicle, and that can only be determined by a qualified mechanic with diagnostic equipment. If a warning light is illuminated, the most reliable next step is professional diagnosis.
What does P0152 mean?
P0152 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: O2 Sensor Circuit High Voltage (Bank 2 Sensor 1).
This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms commonly associated with this code
Symptoms that drivers often report alongside this code. Not all may apply to every case:
- • Engine warning light on, frequently with no change in how the car drives
- • Fuel economy creeps up because the ECU leans the mixture to compensate for the false rich reading
- • Rough idle or a flat spot under acceleration on some engines
- • Occasional black smoke from the tailpipe if the car is running rich
- • Faint petrol smell at the exhaust under load
- • On plenty of cars, nothing you'd notice without a scan tool
Possible causes
Causes commonly associated with P0152, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. Failed sensor, either contaminated internally or with a short that holds the signal high. This is the usual culprit on higher-mileage cars
- 2. Damaged wiring between the sensor and ECU, often where the loom runs near the hot exhaust and the insulation has melted or chafed through
- 3. The signal wire shorting across to the heater feed, which pushes the reading sky-high
- 4. A leaking or stuck injector on bank 2 dumping in extra fuel and creating a real rich condition
- 5. Oil or coolant on the sensor tip, usually a sign of a worn engine or a head gasket starting to weep
- 6. Corroded or loose connector at the sensor, common after a few British winters of salt and damp
How mechanics typically diagnose
A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training.
- 1. Read the live O2 data for both banks side by side. If bank 2 sensor 1 is stuck high while bank 1 swings normally, you've isolated the problem to one bank straight away
- 2. Inspect the bank 2 sensor 1 wiring and connector for melted insulation, green corrosion, or the loom resting against the manifold. A surprising number of these are just a chafed wire
- 3. Check the fuel trims. Strongly negative long-term trim on bank 2 points to a genuine rich condition rather than a duff sensor
- 4. Back-probe the sensor signal wire and check the voltage against the connector. A short to the heater supply will show up here
- 5. Look at the sensor tip once it's out. Black sooty fouling suggests rich running, oily or white deposits point to an engine that's burning oil or coolant
- 6. If the wiring checks out and the sensor reads normally on the bench, only then start questioning the ECU input circuit
Common questions about P0152
Can I keep driving the car like this? +
For short trips and getting to a garage, yes, it's not going to leave you stranded. The risk is the ECU leaning out bank 2 to correct for a false rich signal, which over weeks of driving can run that bank hotter than ideal and hurt your fuel economy. If the car is also blowing black smoke or stumbling, get it looked at sooner rather than letting it run for months.
Is this going to be an MOT problem? +
The code on its own isn't a fail, but if the engine light is glowing when the tester plugs in or eyeballs the dash, that counts against you under the current rules. And if the sensor fault has the bank running rich, the emissions readings at the tailpipe can tip over the limit and fail the gas test directly. Sort the fault and clear the light a few drive cycles before you book it in.
What am I likely to pay to get it sorted? +
If it's the sensor, an upstream O2 sensor for most V6 and V8 cars runs roughly £40 to £120 for the part, with an independent garage fitting it for around £100 to £200 all in. A wiring repair can be cheaper if it's just a chafed section to splice. A main dealer will charge more on labour, often £250 to £400 for the same job, and if a stuck injector or oil contamination turns out to be the real cause you're into bigger money for that repair on top.
Information only, not professional advice
The information on this page is provided for general guidance and educational purposes only. It is not a substitute for diagnosis or repair advice from a qualified mechanic. Always verify any fault before paying for repairs. carfaultcodes.co.uk accepts no liability for decisions made based on this information. Full terms →