Fix P2273: Mechanic’s solutions that WORKED

The P2273: O2 Sensor Signal Biased/Stuck Rich Bank 2 Sensor 2 code signifies a problem in the oxygen sensor circuit for Bank 2, Sensor 2, located on the side of the engine opposite to the first cylinder. This sensor measures the amount of oxygen in the exhaust gas and sends this data to the PCM. The code is set when the PCM detects a signal from the sensor that consistently indicates a rich condition, meaning an excessive amount of fuel in the exhaust.

P2273 quick overview

Meaning	P2273: O2 Sensor Signal Biased/Stuck Rich Bank 2 Sensor 2
Is it serious?	This code indicates an issue with the vehicle’s emissions system and while it may not cause immediate breakdown, it should be addressed to avoid potential long-term engine damage or failed emissions tests.
Possible causes	– Faulty or failing oxygen sensor (Bank 2, Sensor 2) – Exhaust leaks near the oxygen sensor – Shorted or open wiring in the O2 sensor circuit – Contaminated or damaged O2 sensor – Issues with the fuel pressure or injectors causing a rich condition – Problems with the Powertrain Control Module (PCM)
How to diagnose?	Check O2 Sensor: Inspect the Bank 2, Sensor 2 oxygen sensor for any signs of damage or contamination. Inspect Wiring and Connectors: Examine the wiring and connections to the oxygen sensor for shorts, opens, or corrosion. Test Sensor Functionality: Use a multimeter or diagnostic tool to test the oxygen sensor’s functionality and output voltage. Scan for Additional Codes: Use a diagnostic scanner to check for other codes that might provide clues to the underlying issue. Inspect Fuel System: Check the fuel pressure and injectors for issues that might cause a rich condition. Evaluate PCM: Consider the PCM as a potential cause only after ruling out other more common issues.

How to fix P2273 – learn from mechanics

I looked into P2273 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: Ford

Vehicle Information: 2014 Ford E-250 5.4L, MIL Lamp on

Issue + Repair History:

• Initially, a check engine light for bank 1 sensor 1 O2 sensor, followed by misfires, power issues, and dying issues.
• Replaced front O2 sensors, performed BG injector service, changed plugs and coil boots.
• New catalytic converters installed due to blockage.
• Ran smoke machine, no vacuum leaks found.
• Fuel pressure stable at 55 psi.
• Tried a new mass airflow sensor but no change.
• Cylinder balance test showed all cylinders missing slightly, 1 to 15, changing frequently.

Other OBD2 Codes + Test Results:

• P2196: O2 sensor signal biased/stuck rich (Bank 1 Sensor 1)
• P2198: O2 sensor signal biased/stuck rich (Bank 2 Sensor 1)
• P2271: O2 sensor signal biased/stuck rich (Bank 1 Sensor 2)
• P2273: O2 sensor signal biased/stuck rich (Bank 2 Sensor 2)

Suggestions to Fix Issue:

1. Reset KAM (Keep Alive Memory) after repairs and re-evaluate.
2. Disconnect EVAP purge valve and check the carbon canister for raw fuel.
3. Consider the possibility of a leaky fuel injector.
4. Verify if the new MAF sensor is OE or aftermarket, and whether it’s new or remanufactured.
5. Check for extended crank after shutdown, indicating a bad injector.
6. In case of a flex-fuel system, check the alcohol percentage and consider a KAM reset.
7. Investigate if O2 sensors might be plugged into wrong connectors, confusing the PCM.

Final Fix:

• The problem was resolved by identifying and replacing a faulty vent valve on top of the engine. This issue was intermittent and not apparent all the time.

Case #2: Ford

Vehicle Information: 2008 Ford F-150 Lariat 5.4L, Poor Idle Quality, Misfire, MIL Lamp on

Issue + Repair History:

• Truck initially came in for a safety and emissions test, passed both.
• Noticed timing chain noise at idle, customer agreed to new timing kit installation.
• Replaced timing chain guides, chains, tensioners, and new OEM spark plugs.
• Post-repair, the truck ran poorly with check engine light on, setting codes P0349 and P0345.
• At operating temperature, rich codes appeared, with a noticeable rich condition smell.
• Checked power at CMP sensor, found no power on either CMP sensor or at the PCM.
• All fuses, powers, and grounds checked and found no faults.

Computer Codes & Descriptions:

• P0349: Camshaft Position Sensor A Circuit Intermittent (Bank 2)
• P0345: Camshaft Position Sensor A Circuit Malfunction (Bank 2)
• P2271: O2 Sensor Signal Biased/Stuck Rich (Bank 1 Sensor 2)
• P2273: O2 Sensor Signal Biased/Stuck Rich (Bank 2 Sensor 2)

Suggestions to Fix Issue:

1. Check if wires are crossed and the condition of the CKP circuit.
2. Assess the oil pressure when hot and idling in gear.
3. Investigate if reference voltage to both cam sensors is being shorted to ground.
4. Confirm if cam phasers were replaced.
5. Explore the possibility of a short in the reference voltage to ground.
6. Examine VCT electrical connector, phaser marks/posts, and check for bent phaser posts.
7. Check both actuator solenoids for sticking.
8. Look for a bent tone ring on the phaser.
9. Consider redoing the timing chain installation, including replacing solenoids and checking oil pressure.

Final Fix:

• The issue was resolved after rechecking the timing setup. Bank 2 was found to be 2 teeth off. Correcting this mistake fixed the problems. The diagnostic flow chart initially led to incorrect conclusions, indicating the importance of double-checking mechanical work.

Case #3: Pontiac

Vehicle Information: 2008 Pontiac G6 GXP 3.6L, Poor Fuel Economy, MIL Lamp on

Issue + Repair History:

• Customer reported lack of power and poor fuel economy.
• Scanned and found multiple codes, performed visual inspection of cam sensors and solenoids.
• Cleared codes, but P0017 reappeared after a road test.
• Attempted cam system check with scanner, but was unable due to the code.
• The customer reported hearing a thunk during start-up, problems started shortly after.
• Considering the possibility of issues with the timing chains.

Computer Codes & Descriptions:

• P0011: Intake CMP Performance BK1
• P0014: Exhaust CMP Performance BK1
• P0017: CKP to CMP Correlation BK1 EXH
• P0021: Int CMP Performance BK2
• P0171: Lean BK1
• P2273: O2 BK2 S2 Signal Malfunction

Suggestions to Fix Issue:

1. Consider replacing the timing chain set due to possible stretching.
2. Scope CKP and cam signals, compare with known good waveforms.
3. Check oil condition and level.
4. Swap cam solenoid to different position to see if code follows.
5. Check for any PCM updates or special policies for this model.
6. Recommend replacing water pump along with timing chains.

Final Fix:

• The final decision was pending customer consideration of repair costs. The mechanic suspected the issue to be related to the timing chains. The possibility of stretched chains was strongly indicated by community feedback. Customer was informed about checking with GM regarding the issue. Repair outcome was contingent upon customer’s decision to proceed.

Case #4: Chevrolet

Vehicle Information: 2008 Chevrolet Silverado 1500 WT 4.3L, Excessive Emissions, Poor Idle Quality, Surge, Poor Fuel Economy, MIL Lamp on

Issue + Repair History:

• Truck running rough with check engine light and reduced engine power light on.
• Scanned and found 11 codes including P0172, P0175, P0068, P0101, P2272, P2270, P0106, P0121, P0507, P1101, P2273.
• MAF readings fluctuated between 5.4 to 21.5 g/sec, coolant sensor readings varied between 100 to 245 degrees rapidly.
• Replaced coolant temperature sensor and mass airflow sensor, but no change in data or performance.
• TPS 1 and 2, TAC command, and fuel trims also showed fluctuations.
• Fuel pressure was slightly higher than normal (64 psi running, 60 psi off).

Computer Codes & Descriptions:

• P0172: Fuel Trim Rich Bank 1
• P0175: Fuel Trim Rich Bank 2
• P0068: Throttle Body Airflow Performance
• P0101: Mass Air Flow Sensor Performance
• P2272: HO2S Signal Stuck Lean Bank 2 Sensor 2
• P2270: HO2S Signal Stuck Lean Bank 1 Sensor 2
• Plus additional codes P0106, P0121, P0507, P1101, P2273

Suggestions to Fix Issue:

1. Replace the throttle body and MAF sensor.
2. Check for wire harness rubbing through anywhere.
3. Rule out a wiring problem or questionable ground connection.
4. Clean fuel injectors and check all grounds, especially near the battery.
5. Check all fuses, battery, engine, and chassis ground strap connections.
6. Monitor TP values while manipulating the harness 3 wire connector at TP sensor at the throttle body.
7. Consider a possible throttle body problem, recommend idle learn and clean MAF, replace air filter.
8. Check all power and grounds to PCM.

Final Fix:

• The problem was resolved by replacing the ECM (Electronic Control Module) after the customer took the vehicle to the dealer. The ECM replacement was done under warranty. The technician had checked all grounds and found no faults, leading to the eventual conclusion that the PCM was the issue.

Case #5: Jeep

Vehicle Information: 2011 Jeep Wrangler Unlimited Sahara 3.8L, MIL Lamp on

Issue + Repair History:

• Vehicle failed emission test and was brought in with CEL on.
• Unable to clear DTCs: P0031, P0051, P0037, P0057, P0158, P0138, P2271, P2273.
• Performed tests as per flowcharts, but no results.
• Heater circuits tested at 4.4 to 4.5 ohms, good ground at all sensors.
• Power backprobe for all sensors showed voltage bouncing between 1.1 to battery voltage.

Computer Codes & Descriptions:

• P0031: O2 Sensor B1S1 Heater Circuit Low
• P0051: O2 Sensor B2S1 Heater Circuit Low
• P0037: O2 Sensor B1S2 Heater Circuit Low
• P0057: O2 Sensor B2S2 Heater Circuit Low
• P0158: O2 Sensor B2S2 Circuit High
• P0138: O2 Sensor B1S2 Circuit High
• P2271: O2 Sensor B1S2 Signal Stuck Rich
• P2273: O2 Sensor B2S2 Signal Biased Rich

Suggestions to Fix Issue:

1. Check if the PCM needs to be replaced, as it might falsely indicate all O2 heater circuits are bad.
2. Conduct voltage drop testing and confirm battery voltage for heater circuits.
3. Power up the sensors’ heater circuits through an ammeter to ensure wiring can support the load.
4. Run the heater test on the scanner, expecting voltage drop to full lean within 90 seconds.
5. Check wiring to O2 sensors for chafing and ensure OEM sensors are installed.

Final Fix:

• After extensive testing, it was determined that all O2 sensors shorted out and the PCM had an internal short on the O2 signal terminal.
• Replaced the PCM and all O2 sensors, followed by reprogramming the PCM.
• After the repair and reprogramming, the vehicle tested all ok.
• The delay in closing the request was regretted, and thanks were extended for the support received.

Advice	Brief Description of Diagnostic Step
Check O2 Sensors	Inspect the oxygen sensors for any signs of malfunction or failure, as they are often directly related to P2273 code.
Verify Wiring and Connections	Ensure that the wiring and connections related to the O2 sensors are intact and free from damage, as issues here can cause the P2273 code.
Consider PCM Issues	In cases where O2 sensors and wiring are not at fault, consider the possibility of a malfunctioning Powertrain Control Module (PCM).
Check Fuel Trims	Monitor the fuel trim readings, as they can indicate a rich or lean condition contributing to the P2273 code.
Inspect for Exhaust Leaks	Check the exhaust system for leaks, as these can affect O2 sensor readings and lead to a P2273 code.
Ensure Correct O2 Sensor Installation	Make sure the oxygen sensors are installed correctly and are the correct type for the vehicle, as incorrect sensors can trigger the P2273 code.