What Does P015D Mean?
The O2 sensor on Bank 2, Sensor 1 (upstream, pre-catalytic converter) is exhibiting a delayed response when transitioning from a lean exhaust condition to a rich condition. The PCM has measured the specific delay time from when the exhaust goes rich to when the sensor voltage crosses the rich threshold, and it exceeds the allowed limit. This primary fuel control sensor's delayed response directly impacts fuel mixture accuracy during acceleration and load application. The driver may notice occasional hesitation and reduced fuel economy.
Common Causes
40%
Degraded O2 sensor with increased delay on the lean-to-rich transition
20%
Oil or coolant deposits on the sensing element reducing its reactivity
20%
Exhaust leak on Bank 2 introducing air that delays the rich detection
10%
Wiring or connector fault causing signal attenuation in the sensor circuit
10%
Vacuum leak on Bank 2 intake side creating a lean bias that masks enrichment
Diagnostic Steps
1
Monitor Bank 2 Sensor 1 voltage during a snap throttle test — the sensor should rise above 0.7V within 100-150ms of the throttle snap; a delayed sensor will take 300ms+ to detect the rich condition.
2
Graph Bank 2 Sensor 1 alongside Bank 1 Sensor 1 during the same throttle event — both upstream sensors should respond at similar speeds; a lagging Bank 2 confirms the fault.
3
Check Bank 2 STFT during acceleration events — if STFT swings significantly positive during tip-in, the sensor delay is preventing timely feedback correction.
4
Perform a vacuum leak test on Bank 2 intake using a smoke machine — unmetered air creates a lean bias that makes the sensor appear even slower to transition rich.
5
Inspect the O2 sensor connector for heat damage, corrosion, or water intrusion — measure signal wire resistance (should be less than 1 ohm end-to-end) and verify heater operation.
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 lean exhaust condition to a rich condition. The PCM has measured the specific delay time from when the exhaust goes rich to when the sensor voltage crosses the rich thresh...
The most common cause of P015D (O2 Sensor Delayed Response - Lean to Rich (Bank 2 Sensor 1)) is: Degraded O2 sensor with increased delay on the lean-to-rich transition
Typical repair costs for P015D 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 lean-to-rich response means the engine may momentarily run lean during acceleration on Bank 2, which can cause lean misfires and elevated catalytic converter temperatures. Repair within a few hundred miles to prevent secondary damage.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P015D 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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