P0154 = O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 1).

What P0154 Means (In Real Terms)

Bank 2 Sensor 1 = Upstream O2 sensor on the bank without cylinder #1

“No activity” = ECU sees the sensor stuck (usually ~0.45V) or no signal change

The ECU expects this sensor to switch rapidly when the engine is warm

Most Common Real-World Causes (In Order)

1. Dead or Contaminated O2 Sensor (Very Common)

Sensor internally failed

Silicone, coolant, oil contamination

Aged sensor (100k+ km / 60k+ miles)

📌 If mileage is high → replace first

2. Wiring / Connector Issues (Very Common)

Melted wires near exhaust

Broken signal wire inside insulation

Corrosion in connector

Poor ground

📌 Especially common on V6 / V8 engines

3. Heater Circuit Not Working

If the heater fails, sensor stays cold → no activity

Blown fuse

No 12V or ground to heater

Internal heater failure

📌 This may NOT always set a heater-specific code

4. Exhaust Leak Before Sensor

Cracked manifold

Leaking gasket

Small leaks = false oxygen readings or no switching

5. Fuel / Engine Condition (Less Common)

Injector not firing on Bank 2

Vacuum leak only on Bank 2

Very lean condition

Professional Diagnostic Steps (Fast Workflow)

🔧 Step 1: Live Data (Best Test)

Warm engine, monitor B2S1 voltage:

Normal: 0.1–0.9V switching

Bad sensor: stuck ~0.45V or 0V

Lazy sensor: slow response

📌 Compare with Bank 1 Sensor 1

🔧 Step 2: Force Reaction Test

Add propane or carb cleaner → voltage should jump rich (>0.8V)

Create vacuum leak → voltage should drop lean (<0.2V)

❌ No reaction = bad sensor or wiring

🔧 Step 3: Heater Circuit Test

Key ON: check for 12V supply

Resistance test: usually 3–14 ohms (check spec)

Check ground integrity

🔧 Step 4: Wiring Wiggle Test

Wiggle harness while watching live data

Any spike = wiring fault

Quick Decision Guide (Shop Use)

Test Result Likely Fix

No voltage change Replace O2 sensor
No heater power Repair power/ground
Sensor works when forced Check exhaust leak / fuel
Both banks affected ECU / fuel issue
Only Bank 2 affected Sensor or wiring

✅ Use OEM or high-quality brand (Denso, Bosch, NTK)
❌ Avoid universal sensors unless necessary
🔩 Anti-seize only if not pre-coated
🔥 Clear codes + road test until closed loop

Welcome To Madurai Car Service 💐🙏.