Fix P0154: Mechanic’s solutions that WORKED

The code P0154 – O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 1) indicates a lack of activity in the oxygen sensor circuit on Bank 2 Sensor 1. This typically points to an issue with the sensor itself or its surrounding components and is most likely caused by wiring problems, exhaust leaks, or a faulty sensor.

P0154 quick overview

Meaning	P0154 – O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 1)
Is it serious?	It can lead to increased emissions, poor fuel economy, and potential damage to the catalytic converter if not addressed.
Possible causes	– Faulty or contaminated oxygen sensor – Incorrectly installed oxygen sensor – Wiring or connection issues for the oxygen sensor – Exhaust leaks near the oxygen sensor – Faulty PCM/ECU – Software needing an update or reflash
How to diagnose?	Inspect the O2 Sensor Wiring: Check for any damaged, frayed, or incorrect wiring and connections. Test the O2 Sensor Functionality: Use a scanner to monitor the oxygen sensor’s voltage readings and response time. Examine the PCM/ECU: Ensure the vehicle’s computer is functioning correctly and has the latest updates. Investigate the Exhaust System: Look for any leaks or damage that could affect the sensor’s readings. Review Fuel Trims: Analyze the fuel trim data for any irregularities that could indicate a mixture issue. Test the O2 Sensor Heater Circuit: Verify the heater circuit has proper power and ground. Perform a Smoke Test: Conduct a smoke test to identify any vacuum leaks. Check for Software Updates: Ensure the vehicle’s software is up to date.

In plain language, code P0154 means that the computer in your car isn’t getting a signal from one of the sensors that helps control how much fuel goes into the engine. This could be because the sensor is broken, something is wrong with the wires, or there’s a leak in the part of the exhaust system near the sensor. It’s like having a broken thermometer; your car can’t tell if it’s running too hot or too cold, which can cause other problems if not fixed.

How to fix P0154 – learn from mechanics

I looked into P0154 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Chrysler

Vehicle Information 1996 Chrysler LHS 3.5L

Issue + Repair History

• MIL Lamp on
• Codes: P0134, P0154
• Previous repairs: Multiple new OEM O2 sensors installed, PCM reflashed

Other OBD2 Codes + Test Results

• No additional codes mentioned

What Are People Suggesting to Fix Issue

• Check if dealing with the correct sensor (Bank 1 vs Bank 2)
• Consider replacing sensors in pairs

What Was the Final Fix

• Installed a matching new O2 sensor
• Realized the initial sensor replacement was misidentified (Bank 1 was actually on the right side, not left)
• Recommendation to replace sensors in pairs in the future

Case #2: Ferrari

Vehicle Information 1997 Ferrari 355 Spider 3.5L

Issue + Repair History

• MIL Lamp on
• Code: P0154 (Bank 2 Sensor 1, no activity detected)
• Previous repairs: Both O2 sensors on bank 2 replaced

Other OBD2 Codes + Test Results

• No additional codes mentioned

What Are People Suggesting to Fix Issue

• Suggestions not explicitly mentioned

What Was the Final Fix

• Installed a new lambda control unit
• Reset codes, which resolved the problem

Case #3: Mitsubishi

Vehicle Information 2003 Mitsubishi Diamante LS 3.5L

Issue + Repair History

• MIL Lamp on
• Code: P0154 (Oxygen sensor circuit malfunction, bank 2 sensor 1)
• Previous repairs: Replaced bank 2 sensor 1 with OEM sensor

What Are People Suggesting to Fix Issue

• Replace in pairs (bank 2 sensor 2)
• Check readings/switching times
• Use a different scanner for accurate diagnosis

What Was the Final Fix

• Replaced bank 2 sensor 2
• Resolved confusion caused by the scanner displaying incorrect sensor activity
• Code resolved after replacing the correct sensor

Case #4: Chevrolet

Vehicle Information 1999 Chevrolet K1500 Suburban 5.7L

Issue + Repair History

• Multiple codes initially, leading to PCM replacement
• Persistent code: P0154 (Low activity b2 s1)
• Replaced oxygen sensor, repaired exhaust crack
• Fuel trim for b2 not optimal due to sensor issue preventing closed loop

What Are People Suggesting to Fix Issue

• Add propane to enrich mixture and check O2 voltage response
• Replace oxygen sensor with a factory sensor
• Check heater circuit for affected oxygen sensor
• Create a vacuum leak or add carb cleaner to check for changes
• Scope O2 voltage at the sensor and PCM
• Verify PCM reporting correctly
• Ensure working on the correct circuit/sensor

What Was the Final Fix

• Replaced the remanufactured PCM with a different one, resolving the issue

Case #5: Honda

Vehicle Information 2000 Honda Passport EX 3.2L

Issue + Repair History

• Runs well in open loop, issues in closed loop with one bank loading up
• Fuel trim -33 on one bank, 28 on the other in closed loop
• Suspected gutted converters due to noise
• Front O2 sensors not fluctuating at 2500rpm

What Are People Suggesting to Fix Issue

• Perform an injector balance test for potential sticking or leaking injector
• Check if O2 sensor wiring got swapped side to side
• Investigate tight valve clearances
• Examine intake valve, intake, crankcase vent, evaporative emission valve
• Verify oxygen sensors are functioning correctly
• Check for engine breathing problems, valve timing
• Inspect intake gaskets and fuel pressure regulator for leaks

What Was the Final Fix

• The front O2 sensor wires were crossed, correcting this resolved the issue

Advice	Diagnostic Step
Check O2 Sensor Wiring	Verify the wiring and connections for the O2 sensors are correct and not swapped or damaged.
Inspect O2 Sensor Functionality	Test the oxygen sensors to ensure they are functioning properly and responding to changes in fuel mixture.
Examine PCM/ECU	Confirm the vehicle’s computer (PCM/ECU) is functioning correctly and has the latest software updates.
Investigate Exhaust System	Check the exhaust system for leaks or damage that could affect O2 sensor readings.
Review Fuel Trims	Analyze the fuel trim data to identify potential issues with fuel delivery or air intake.
Test O2 Sensor Heater Circuit	Verify the heater circuit of the O2 sensor has proper power and ground.
Consider Replacing in Pairs	If one O2 sensor is faulty, consider replacing both sensors on the same bank to ensure balanced readings.
Ensure Correct Sensor Replacement	Double-check that the correct O2 sensor was replaced, as misidentification can occur.
Perform Smoke Test	Conduct a smoke test to identify any vacuum leaks that could affect O2 sensor readings.
Check for Software Updates	Ensure the vehicle’s software is up to date, as some issues may be resolved with a software reflash.