What Does P015C Mean?
The O2 sensor on Bank 2, Sensor 1 (upstream, pre-catalytic converter) is exhibiting a delayed response when transitioning from a rich exhaust condition to a lean condition. The PCM has measured the specific delay time and it exceeds the calibrated threshold. As the primary fuel control sensor for Bank 2, this delay means the PCM cannot promptly detect when the exhaust goes lean, leading to potential over-fueling during transitions. The driver may notice slightly reduced fuel economy.
Common Causes
40%
Aging O2 sensor with increased response delay on the rich-to-lean transition
20%
Sensor element contamination from oil, coolant, or fuel additive residue
20%
Exhaust leak near the Bank 2 exhaust manifold introducing false air
10%
High-resistance sensor signal wiring or connector corrosion
10%
Persistent rich condition on Bank 2 from injector or fuel pressure issue delaying the lean transition
Diagnostic Steps
1
Monitor Bank 2 Sensor 1 voltage during a deceleration fuel cutoff from 3000 RPM — the sensor voltage should drop below 0.2V within 100-150ms; delayed response will show a slow, gradual decline.
2
Compare the rich-to-lean transition time of Bank 2 Sensor 1 to Bank 1 Sensor 1 — both should be within similar ranges; a significantly slower Bank 2 confirms the fault.
3
Check Bank 2 STFT and LTFT — if LTFT is more negative than Bank 1, the delayed lean response is causing the PCM to over-correct with less fuel.
4
Inspect the Bank 2 exhaust manifold for cracks, loose bolts, and gasket leaks — carbon tracking and soot deposits indicate leak locations.
5
If the sensor has significant mileage (80K+ miles), the sensing element is likely degraded beyond acceptable response times and replacement is warranted.
Estimated Repair Cost
$100 - $400
Parts + labor, varies by vehicle and location
The O2 sensor on Bank 2, Sensor 1 (upstream, pre-catalytic converter) is exhibiting a delayed response when transitioning from a rich exhaust condition to a lean condition. The PCM has measured the specific delay time and it exceeds the calibrated threshold. As the primary fuel control sensor for Ba...
The most common cause of P015C (O2 Sensor Delayed Response - Rich to Lean (Bank 2 Sensor 1)) is: Aging O2 sensor with increased response delay on the rich-to-lean transition
Typical repair costs for P015C range from $100 to $400, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Drive with awareness. The delayed response on this primary fuel control sensor causes imprecise fuel management during deceleration and off-throttle transitions, leading to increased emissions and potential catalytic converter stress over time. Schedule repair soon.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P015C to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel System / Emissions
Difficulty
Type
Generic (SAE)
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