P014A - Oxygen Sensor (O2) Delayed Response - Rich to Lean (Bank 2 Sensor '2')
System
Powertrain (Engine & Gearbox)
Technical Description
The control module has detected a fault in the Oxygen Sensor (O2) Delayed Response (P014A). Pertains to downstream oxygen sensor (post-catalyst diagnostic sensor) evaluating catalytic converter conversion efficiency.
Multimeter Test Points & Nominal Values
| Test Point / Component | Measurement | Nominal Target Range | Test Condition |
|---|---|---|---|
| Oxygen Sensor (O2) Delayed Response (Downstream Diagnostic Sensor) – Heater Resistance (Cold) | Resistance (Ω) | 8.0 - 16.0 Ω | Disconnected plug at 20°C |
| Oxygen Sensor (O2) Delayed Response (Downstream Diagnostic Sensor) – Signal Voltage | Voltage (V) | 0.55 - 0.75 V (steady plateau) | Warm engine at steady highway cruise (2000 RPM) |
| Catalytic Conversion Oxygen Index | Signal (Index) | > 0.85 (healthy oxygen storage capacity) | Warm engine, closed loop |
Disconnected plug at 20°C
Warm engine at steady highway cruise (2000 RPM)
Warm engine, closed loop
Oscilloscope Waveform Analysis
1 s/div, 200 mV/divPossible Causes
Bank 2 specific:Inspect wiring harness to cylinder bank 2 (radiator/left bank, exposed to vibration and moisture).
Sensor 2 (Downstream post-cat):Inspect underbody wiring for mechanical road-debris damage or water intrusion inside the subframe connector.
Chafed or pinched wiring harness along the signal path to Oxygen Sensor (O2) Delayed Response
Poor ground connection or excessive voltage drop (> 0.1 V) at the ground point for Oxygen Sensor (O2) Delayed Response
Defective internal output driver or reference circuit in the control module for Oxygen Sensor (O2) Delayed Response
Symptoms
5
Recommended Solution
Monitor downstream sensor voltage at steady cruise (should hold steady between 0.55 and 0.75 V; active switching flags depleted catalyst).
Cross-swap the component on Bank 2 with Bank 1 to rule out mechanical oil passages and internal timing wear.
Review freeze-frame environmental data and perform fundamental voltage-drop and resistance checks on the circuit.
Verify loaded supply voltage and harness terminal pins at Oxygen Sensor (O2) Delayed Response.
Check circuit continuity and ground-side voltage drop (< 0.05 V) for Oxygen Sensor (O2) Delayed Response.
For wideband sensors:monitor pump current (mA) and lambda in scan Live Data during snap-throttle and decel fuel cut.
Mechanic's Tip
O2 sensors measure free oxygen, not fuel. An exhaust leak upstream of the sensor pulls in atmospheric air via venturi pulses, forcing false lean readings and causing the ECM to severely over-fuel.