P0158 = O2 Sensor Circuit High Voltage
Bank 2 – Sensor 2

👉 This is a downstream (post-catalytic converter) oxygen sensor on Bank 2.

What “High Voltage” means

Normal downstream O2 voltage: ~0.1V – 0.9V

“High voltage” usually means:

Sensor stuck above ~0.9V

Or PCM sees a short to power

This does NOT usually affect drivability, but it will trigger a check engine light and may cause failed emissions.

Common causes (in real-world order)

1. Bad O2 sensor (most common)

Sensor internally shorted

Contaminated by oil, coolant, or rich fuel condition

✅ Very common on higher-mileage vehicles

2. Wiring issue

Check for:

Melted wires near exhaust

Short to 12V power

Damaged insulation

Corrosion in connector

⚠️ Downstream sensors live close to heat → wiring failures are common

3. Exhaust issues

Exhaust leak before the sensor

Damaged catalytic converter

4. Engine running rich (less common)

Leaking injector on Bank 2

Fuel pressure too high

This usually comes with other codes.

How to diagnose fast (shop method)

Step 1: Look at live data

Monitor B2S2 O2 voltage

If it’s stuck at ~0.9–1.0V, that’s your problem

Step 2: Unplug the sensor

If voltage drops to 0V → sensor is bad

If voltage stays high → wiring short to power or PCM issue

Step 3: Visual inspection

Follow the harness from sensor to main loom

Look for:

Burn marks

Crushed wires

Oil contamination

Step 4: Check heater circuit (optional but smart)

Heater resistance usually 3–14 ohms

Blown heater fuse can cause weird readings

Repair recommendation (what I’d tell a customer)

Replace Bank 2 Sensor 2 O2 sensor

Use OEM or high-quality aftermarket

Clear codes and perform a drive cycle

💡 Do not replace the catalytic converter unless you have efficiency codes (like P0430)

Welcome To Madurai Car Service 💐🙏.