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P0152 means bank 2 upstream sensor is reading rich. Often the engine actually IS running rich on that bank - leaking injector, bad fuel pressure regulator, or stuck purge valve. Driving long with a rich condition kills the catalytic converter, so don't put this off. See fuel pressure gauges on Amazon ↗
These are statistical causes across ALL vehicles - your exact car may rank differently
For example, on a Honda 4-cyl the downstream O2 sensor causes P0152 64% of the time, but on a GM 5.3L V8 the catalytic converter is the cause 71% of the time. Get a probability ranking built specifically for your year, make, model, and mileage.
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🎯 Top Causes & Probability
35%
#1 - Most Likely
Bank 2 Rich Condition (Leaking Injector / High Fuel Pressure)
A leaking or stuck-open injector on bank 2, a stuck-open EVAP purge valve, or a failed fuel pressure regulator pushes the bank 2 mixture rich, and the sensor reports correctly. Bank 2 LTFT below -10% confirms a true rich condition.
🔩 Part
$25–$400
👨🔧 Labor
$80–$300
⚡ DIY Difficulty
Medium
25%
#2 - Check First
Failed Upstream O2 Sensor (Bank 2, Sensor 1)
The sensor element has degraded and outputs a stuck-high voltage regardless of actual exhaust composition. Common past 80k miles. Replacement is the fix when fuel trims are normal.
🔩 Part
$40–$220
👨🔧 Labor
$50–$150
⚡ DIY Difficulty
Easy
20%
#3 - Less Common
Sensor Contamination (Coolant, Oil, Silicone)
A head gasket leak letting coolant into bank 2, oil consumption, or non-O2-safe RTV silicone coats the sensor and pegs it high. Replacing the sensor without fixing the contamination shortens the new sensor's life dramatically.
🔩 Part
$40–$300
👨🔧 Labor
$50–$400
⚡ DIY Difficulty
Medium
10%
#4
Signal Wire Shorted to Voltage
A chafed signal wire touching a 12V or 5V source pegs the sensor reading high. Inspect the bank 2 sensor harness, especially where it routes near the exhaust manifold.
🔩 Part
$5–$60
👨🔧 Labor
$50–$150
⚡ DIY Difficulty
Medium
🚗 Most Affected Vehicles
🔧 Step-by-Step Diagnosis
- Read Bank 2 Long-Term Fuel Trim - Watch LTFT on bank 2. Below -10% confirms a real rich condition - chase that cause (leaking injector, fuel pressure regulator, purge valve) first. Around 0% with a stuck-high sensor means the sensor itself is bad.
- Bleed-Down Fuel Pressure Test - After shutdown, watch fuel pressure with a gauge. If it drops fast and the engine starts hard, a leaking injector or regulator is dumping fuel into the intake on bank 2.
📍 Find a Trusted Shop Near You
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Tips for Choosing a Shop
- Ask if they charge a diagnostic fee and whether it applies toward the repair
- Request a written estimate before approving any work
- Ask specifically about the part brand - OEM vs. aftermarket matters for this code
- Check Google reviews for recent mentions of the specific repair you need