Is P0152 a rich code or a sensor code?

It can be either, and that's the diagnostic question you have to answer first. Read long-term fuel trim on bank 2. If LTFT is heavily negative (-15% or worse), the engine is actually running rich and the sensor is reporting accurately — chase fuel delivery. If LTFT is near zero, the engine is fine and the sensor itself is producing a bad signal — replace the sensor.

What's the difference between P0151 and P0152?

Same sensor, opposite failure modes. P0151 is the sensor stuck at low voltage (reading lean or not reading at all). P0152 is the sensor stuck at high voltage (reading rich, short-circuited, or contaminated). The diagnostic path is different — P0151 makes you check for vacuum and exhaust leaks first, P0152 makes you check fuel delivery and contamination first.

Can a bad O2 sensor damage my catalytic converter?

Indirectly, yes. If the sensor is reporting a falsely rich signal and the PCM responds by leaning out the mixture, you'll be fine. But if the engine is actually running rich and the sensor is accurately reporting it without the PCM being able to correct, the unburned fuel reaching the cat will overheat it. Cats damaged by sustained rich operation usually need to be replaced — a $700-$2,000 repair.

How much will it cost to fix P0152?

Best case is a sensor swap at $150-$400. Mid-range is fixing the cause of an actual rich condition — leaking injector ($300-$700) or stuck EVAP purge valve ($150-$400). Worst case is contamination from internal engine issues, which can run $400-$2,500 depending on whether you're chasing a valve cover gasket or a head gasket. A 15-minute live data check tells you which conversation you're having.

OBD-II trouble code

P0152: O2 Sensor Circuit High Voltage (Bank 2, Sensor 1)

The bank 2 upstream oxygen sensor is reporting voltage stuck high — usually around or above 0.9V — which means the sensor is seeing a rich exhaust mixture, has been contaminated, or has been short-circuited to a voltage source. Different problem set from P0151, even though they sit on the same connector.

Quick facts

System: Powertrain
Category: Fuel & Air / Oxygen Sensor
Severity: Medium severity
Drivable: Usually safe to drive short-term
Repair cost range: $150 – $800
DIY difficulty: Intermediate DIY

What does P0152 mean?

A healthy upstream O2 sensor produces a voltage signal that swings between roughly 0.1V (lean) and 0.9V (rich) as the PCM cycles fuel trim through stoichiometric. P0152 sets when the bank 2 upstream sensor's signal sits high — typically above 0.9V — for longer than the PCM's monitor allows. There are three realistic explanations: bank 2 is actually running rich, the sensor itself has been contaminated or has internally short-circuited, or the sensor's signal wire is shorted to a 12V source somewhere in the harness.

Of those three, the rich condition is the most common on a vehicle that's been driven recently in cold weather, has had a fuel injector replaced recently, or has an aftermarket cold air intake without proper MAF recalibration. A leaking injector — one that drips fuel into the intake even when commanded closed — will push the affected bank rich and produce exactly this code. So will a stuck-open EVAP purge valve dumping fuel vapor into the bank 2 side of the intake.

Sensor contamination is the second most common cause and almost always shows up on engines that have burned oil or coolant. Silicone from the wrong RTV sealant, coolant from a head gasket leak, and oil from worn valve guides will all coat the sensor element and either kill it outright or make it report a falsely rich mixture. A wiring fault — where the signal wire has chafed against a 12V line — is rare but worth checking before condemning a $200 part, especially if other sensors on the same harness are acting up.

Common causes

Leaking fuel injector on bank 2 (running constantly rich)
Stuck-open EVAP purge valve dumping fuel vapor
Excessive fuel pressure from a failed regulator
Contaminated O2 sensor from oil, coolant, or silicone exposure
Internally failed sensor element
Signal wire shorted to a 12V source in the harness
Faulty mass air flow sensor reading low (PCM compensates by adding fuel)
Engine running with the wrong tune file or modified injectors
Recent valve cover gasket leak letting oil reach the upstream sensor

Symptoms

Check engine light on with P0152 stored
Black sooty exhaust at the tailpipe (visible at startup)
Fuel smell from the exhaust
Worse fuel economy than recent weeks
Rough idle, particularly when warm
Long-term fuel trim on bank 2 reading -10% or lower (PCM pulling fuel out)

Diagnostic steps

1.Confirm which side of the engine is bank 2 on your specific vehicle. Don't replace the wrong sensor.
2.Read live data and compare both upstream sensors. If bank 2 is stuck near 0.9V while bank 1 is cycling normally, the problem is isolated to bank 2.
3.Check long-term fuel trim. A reading more negative than -15% on bank 2 confirms the PCM is actively pulling fuel out to compensate for a perceived rich mixture.
4.Inspect the sensor connector and the wiring run for damage, melted insulation, or signs of contact with a 12V line.
5.Visually inspect the sensor tip if you can reach it — a black, sooty coating means it's actually seeing rich exhaust. An oily or wet coating points to engine oil or coolant contamination.
6.If wiring is clean and fuel trim is normal, swap the sensor with the bank 1 sensor. If the high voltage follows the sensor, it's a sensor failure. If it stays on bank 2, you have a fuel delivery issue on that bank.

Repair cost

$150 – $800

Replacing the upstream sensor is $150-$400 in most independent shops, $300-$500 at the dealer. Leaking injector replacement runs $300-$700. EVAP purge valve replacement is $150-$400. If contamination is the cause, the underlying repair — head gasket, valve cover, or rings — can run $400-$2,500 depending on the engine.

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DIY vs shop

This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.