P0152 Code: O2 Sensor Circuit High Voltage (Bank 2 Sensor 1)
Bank 2's front O2 sensor is pinned high – usually voltage leaking in from its heater wire or a leaky injector.
At a glance
Severity: Moderate
- Meaning
- O2 Sensor Circuit High Voltage (Bank 2 Sensor 1)
- System
- Fuel & Air Metering · Powertrain
- Safe to drive?
- With caution
- Typical repair cost
- $50–$700
- DIY difficulty
- Moderate
P0152 is stored when the upstream oxygen sensor on bank 2 holds its signal at or above the top of the normal range, typically over about 1.0 to 1.1 V, for a set period. A zirconia sensor tops out around 0.9 V even in a very rich mixture, so a reading beyond that is suspicious in itself: in most cases voltage is getting into the signal wire from outside, often from the sensor's own 12 V heater feed where the two wires have cooked together near the manifold. A really rich bank 2 can hold the signal near 0.9 V as well, for example a leaking injector on that head or an LPG or fuel system fault on that side. Either way, the ECU believes bank 2 is rich and pulls fuel from that side only, so the practical risk is a lean, misfiring bank 2 while bank 1 carries on normally.
Can I keep driving? Drive gently and get it looked at soon. A false high signal lets the ECU lean out bank 2, which can cause stumbling and lean misfires on those cylinders; a genuinely leaking injector can wash oil off the cylinder walls. If the light starts flashing, stop.
How to read P0152
- P Powertrain
- 0 Generic (SAE)
- 1 Fuel & air metering
- 52 Specific fault
Symptoms
- Check engine light, often with P0175 or misfire codes for bank 2 cylinders
- Stumble or hesitation that seems to come from one side of the engine
- Strong fuel smell, black smoke or a hard hot restart if a bank 2 injector is leaking
- Engine oil level rising and smelling of gasoline
- Fuel economy unchanged or even slightly better when the high signal is false
- Rough idle once bank 2 has been leaned out
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Signal wire picking up heater voltage where the harness has melted near the bank 2 manifold or heat shield
- Leaking or dribbling injector on a bank 2 cylinder making that side genuinely rich
- Sensor contaminated or internally shorted between heater and signal
- Moisture and corrosion in the connector bridging the heater and signal pins
- Universal sensor spliced with heater and signal wires crossed
- Excess fuel pressure, which normally also sets P0132 on bank 1
- Poor sensor ground or ECU input fault
Diagnosis step by step
Read the number, not just the code
In live data a truly rich narrowband sensor sits around 0.8 to 0.95 V. A value pinned at the top of the scale, often displayed as 1.1 to 1.275 V, is electrical, not chemical. Note what the bank 1 sensor reads at the same moment for comparison.
Tools: OBD-II scanner
Check it cold with the engine off
Turn the key on without starting a cold engine. A cold sensor produces almost nothing, so the scanner should show the ECU bias or close to zero. If bank 2 sensor 1 already reads over 1 V, voltage is coming in from the heater circuit or a chafed harness.
Tools: OBD-II scanner
Separate sensor from harness
Unplug the sensor. If the harness side now shows only the normal bias, the fault left with the sensor: measure between each heater pin and the signal pin on the sensor side, which must be open circuit. If the harness still carries several volts on the signal pin, look for a short inside the harness.
Tools: Multimeter
Make bank 2 lean on purpose
At a warm idle, briefly pull off a large vacuum hose to let in unmetered air. A working sensor drops below 0.2 V within about a second. A sensor that stays above 0.8 V with a big air leak is not reporting mixture at all.
Tools: OBD-II scanner
Rule out a really rich bank 2
If the sensor passes the lean test, compare fuel trims: bank 2 long-term trim around -15% or lower with bank 1 near zero means the ECU is fighting extra fuel on that side. Pull the bank 2 spark plugs and look for wet or black ones, and check that fuel pressure holds for several minutes after shutdown; a steady drop points to a leaking injector.
Tools: Spark plug socket, Fuel pressure gauge
Inspect the harness where it's hottest
On transverse V6 engines bank 2 can be the front or the rear row; where it is the rear, as on GM's 3800, the sensor harness is squeezed between the manifold and the firewall. On V8 trucks it runs over the manifold heat shield. Look for fused insulation or wires that have gone stiff and shiny.
Tools: Flashlight
Where the parts are
- 1Upstream O2 sensor
- 2Catalytic converter
- 3Downstream O2 sensor
- 4Diesel particulate filter
- 5Turbocharger
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Repair fused sensor harness and re-route it | No | $100–$300 |
| Replace bank 2 upstream O2 sensor at a shop | No | $200–$480 |
| Replace a leaking bank 2 injector | No | $250–$700 |
| Oil and filter change after fuel dilution | Yes | $50–$120 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Notes by brand
Honda
Many Honda and Acura V6 engines use a wideband air-fuel sensor in the upstream position; on these, bank 2 is usually the front row nearest the radiator. Their upstream sensor faults often appear under other codes, so confirm the exact definition for your engine before ordering a narrowband sensor.
Emissions / smog test impact
Will fail
With P0152 active and the check engine light on, the car fails an OBD-II smog or emissions inspection. Clear the code only after the repair, then drive until the O2 sensor monitor reports ready.
Frequently asked questions
Can an O2 sensor really read more than 1 volt?
Not by itself. A healthy zirconia element produces at most about 1 V, so anything higher comes from outside, most often the heater supply bleeding into the signal wire. That's why the engine-off check is so useful: a cold sensor should show almost nothing.
Why does the engine feel weak on one side?
The ECU trusts the high reading and pulls fuel from bank 2. That bank then runs lean, which you feel as a stumble under load or a lean misfire on those cylinders while bank 1 is fine.
Could a bad fuel pressure regulator cause P0152?
It could, but high fuel pressure affects both banks, so you'd expect P0132 and rich codes on both sides too. When only bank 2 reads high, focus on that side's injectors, wiring and sensor.
Will cleaning the sensor fix it?
No. Solvents and blasting damage the porous coating, and an internal short can't be cleaned away. Fix whatever contaminated or damaged it, then fit a new sensor.