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Home / DTC / P1152 — Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Rich Bank 2

P1152 — Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Rich Bank 2

Detailed page for trouble code P1152.

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P1152

LINCOLN P — Powertrain

Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Rich Bank 2

Brand: LINCOLN
Type: P — Powertrain
Views: UK: 25 EN: 75 RU: 39
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Page language: EN

Causes

  • Faulty upstream (Bank 2) heated oxygen (HO2S) sensor (sensor 1)
  • Open/shorted or poor wiring/connectors to the Bank 2 upstream O2 sensor or heater circuit
  • High fuel pressure or leaking fuel injector(s) on Bank 2
  • Contaminated or slow O2 sensor (coating from coolant, silicone, lead, oil, fuel additives)
  • Faulty mass airflow (MAF) sensor or MAP sensor causing incorrect fueling
  • PCM/ECM fault (rare)

Symptoms

  • Check Engine Light (MIL) illuminated
  • Poor fuel economy (running rich)
  • Rough idle or hesitation
  • Black exhaust smoke or strong fuel odor
  • Failed emissions test (high HC/CO)

What to check

  • Retrieve freeze frame and all stored/active DTCs with a scan tool
  • Monitor live data: upstream O2 sensor (Bank 2 Sensor 1) voltage and switching behavior
  • Compare Bank 1 and Bank 2 upstream O2 sensor outputs
  • Check short-term and long-term fuel trims for Bank 2
  • Inspect wiring and connectors to Bank 2 upstream O2 sensor for damage, corrosion, or loose pins
  • Measure O2 sensor heater resistance and verify heater supply/ground voltage with key ON/engine OFF

Signal parameters

  • Upstream O2 (narrowband) expected switching voltage ~0.1–0.9 V (lean ~0.1–0.3 V, rich ~0.7–0.9 V)
  • Normal switching frequency typically multiple times per second during closed-loop operation
  • Heater circuit resistance commonly 5–10 ohms (varies by sensor) — check OEM spec
  • Heater supply voltage ~12 V with engine off/key on (verify per vehicle)
  • Short-term fuel trim (STFT) should respond within seconds to changes; large negative trims indicate rich condition

Diagnostic algorithm

  1. Verify the code and note freeze frame data. Scan for related codes (fuel trims, MAF/MAP, other O2 sensor codes).
  2. With a capable scan tool, monitor Bank 2 upstream O2 sensor voltage in real time. Observe whether the sensor switches rich/lean quickly during closed-loop operation. Compare to Bank 1 upstream sensor.
  3. Check fuel trims: large negative STFT/LTFT on Bank 2 supports an actual rich condition. If trims are normal and the sensor is fixed high/low, suspect the sensor or wiring.
  4. Inspect the sensor connector and wiring for continuity, corrosion, or damaged insulation. Wiggle-test while monitoring live data for intermittent changes.
  5. Test heater circuit: measure resistance of heater element and verify power and ground at connector with key ON and engine running per OEM procedure.
  6. Backprobe the sensor signal wire and verify voltage at the sensor and at the PCM to rule out open or short in harness.
  7. Check fuel pressure and inspect injectors on Bank 2 for sticking or leaking injectors. Replace or repair fuel pressure regulator if pressure is out of spec.
  8. Check MAF/MAP and intake air system for faults that could cause over-fueling. Clean/replace MAF if required and verify intake for restrictions or vacuum issues.
  9. If wiring and fuel system check OK and sensor does not switch properly, replace the Bank 2 upstream HO2S with a correct OEM or equivalent sensor.
  10. After repairs, clear codes and perform a drive cycle to verify the code does not return and that emissions/fuel trims normalize.
  11. If problems persist after sensor replacement and wiring verified, consider PCM/ECM diagnosis as a last resort.

Likely causes

  • Failed or slow-switching Bank 2 upstream HO2S
  • Heater circuit failure (open heater or no power/ground)
  • Short to voltage/ground in sensor signal circuit
  • Excessive fuel pressure or leaking injector(s) on Bank 2
  • Contaminated sensor due to oil or coolant leaks

Fault status

⚠️ Status
P1152 — Upstream heated oxygen sensor (Bank 2) is not showing expected switch behavior; PCM indicates rich condition on Bank 2. Possible causes include a failed O2 sensor, wiring/connector issues, excessive fueling (fuel pressure/injectors), contaminated sensor, or less commonly an ECM fault. Inspect sensor signal and heater circuits, fuel trims, and related components.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-2.5 hours
166

Browse 166 LINCOLN manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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