Fix P015C: Mechanic’s solutions that WORKED

The code P015C: O2 Sensor Slow Response – Rich to Lean (Bank 2 Sensor 1) indicates a slow response from the oxygen sensor when transitioning from a rich to lean condition, specifically for Bank 2 Sensor 1. This issue is most commonly caused by a faulty sensor, air or exhaust leaks, or fuel delivery problems.

P015C quick overview

Meaning	P015C: O2 Sensor Slow Response – Rich to Lean (Bank 2 Sensor 1)
Is it serious?	Yes, it can lead to poor engine performance, increased emissions, and reduced fuel economy.
Possible causes	– Faulty oxygen sensor – Vacuum leaks – Exhaust leaks near the oxygen sensor – Fuel pressure issues – Contaminated or failing fuel injectors – Wiring or connector problems related to the oxygen sensor – Outdated PCM software
How to diagnose?	1. Visually inspect the oxygen sensor and its wiring for any obvious damage. 2. Check for vacuum and exhaust leaks, particularly near the sensor. 3. Test the fuel pressure to ensure it’s within the manufacturer’s specifications. 4. Inspect the fuel injectors for proper operation and cleanliness. 5. Verify the integrity of the wiring and connectors for the O2 sensor. 6. If all other diagnostics are inconclusive, consider updating the PCM software.

In simpler terms, code P015C means that the oxygen sensor on the second set of cylinders isn’t reacting quickly enough when the fuel mixture changes from rich (too much fuel) to lean (not enough fuel). This can make your car run poorly and use more gas than it should.

How to fix P015C – learn from mechanics

I looked into P015C 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: Chevrolet

Vehicle Information 2013 Chevrolet Suburban 1500 LT 5.3L

Issue + Repair History

• MIL (Malfunction Indicator Lamp) on
• Replaced O2 sensors to solve P013a code
• P015d code persisted (Bank 2 sensor 1 delayed response)

Other OBD2 Codes + Test Results

• P015d: Bank 2 sensor 1 delayed response

What are people suggesting to fix issue

• Perform an exhaust back pressure test
• Check for pinhole exhaust leaks before the O2 sensor
• Use a smoker to pressurize and check for leaks
• Look for a lean condition on bank 2
• Check voltage feed supply to the O2 heaters
• Consider an injector issue, possibly slightly lean

What was the final fix

• Replaced the aftermarket parts with OE (Original Equipment) parts, which resolved the problem.

Case #2: Ford

Vehicle Information 2015 Ford F-150 XLT 3.5L EcoBoost

Issue + Repair History

• MIL (Malfunction Indicator Lamp) on
• Code P015C (O2 Sensor Slow Response – Rich to Lean Bank 2 Sensor 1) present
• Replaced O2 sensor but code returned

Other OBD2 Codes + Test Results

• P015C: O2 Sensor Slow Response – Rich to Lean Bank 2 Sensor 1

What are people suggesting to fix issue

• Check for exhaust leaks before the O2 sensor
• Perform a fuel pressure test to rule out fuel delivery issues
• Inspect the wiring and connectors for the O2 sensor
• Check for proper voltage at the O2 sensor heater circuit
• Consider potential issues with the fuel injectors on Bank 2

What was the final fix

• After trying various suggested fixes, the issue persisted. The final resolution came after updating the Powertrain Control Module (PCM) software, which addressed a known issue with O2 sensor signal processing.

Advice	Description of Diagnostic Step
Check for Exhaust Leaks	Inspect the exhaust system for any leaks, especially before the O2 sensor, as leaks can lead to incorrect readings.
Inspect O2 Sensor Wiring	Examine the wiring and connectors for the O2 sensor to ensure there are no shorts, disconnections, or corrosion.
Verify O2 Sensor Voltage	Check the voltage at the O2 sensor, particularly the heater circuit, to confirm it’s receiving proper power.
Update PCM Software	If all else fails, check for any software updates for the Powertrain Control Module, as outdated software can cause sensor misinterpretation.