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Home / DTC / P1187 — Heated oxygen sensor heater circuit, inferred fault (banks 1 and 2 sensor 1)

P1187 — Heated oxygen sensor heater circuit, inferred fault (banks 1 and 2 sensor 1)

Detailed page for trouble code P1187.

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Code

P1187

LAND ROVER P — Powertrain

Heated oxygen sensor heater circuit, inferred fault (banks 1 and 2 sensor 1)

Brand: LAND ROVER
Type: P — Powertrain
Views: UK: 7 EN: 17 RU: 12
AI status
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Page language: EN

Causes

  • Blown fuse or failed common power feed for O2 heater circuits
  • Open or shorted heater wiring (power or ground)
  • Corroded/loose connector at one or both sensor(s) or at a common junction
  • Failed heater element(s) in the upstream O2 sensor(s)
  • Faulty heater control circuit in the ECM/PCM
  • Battery/charging system low voltage preventing heater operation

Symptoms

  • MIL (Check Engine) lamp illuminated
  • Reduced cold‑start emissions control until sensor warms up
  • Longer warm‑up time before closed‑loop operation
  • Possible rough idle or poor drivability on cold start
  • Reduced fuel economy and elevated emissions until sensors reach operating temp

What to check

  • Read and record freeze‑frame data and all stored/pending codes with scan tool
  • Check for related heater codes (P0135, P0155, etc.) and monitor O2 sensor heater status/live data
  • Visually inspect sensor connectors and wiring harnesses near exhaust/manifolds for heat damage, corrosion, or looseness
  • Check relevant fuses and any heater relay or common power supply
  • Measure resistance of each upstream O2 sensor heater element at the sensor (engine cold)
  • With a multimeter/scan tool, verify supply voltage to heater circuit at connector (key ON) and while commanding heater ON from scan tool

Signal parameters

  • Expected heater supply voltage: ~battery voltage (approx. 11–14 V) when heater commanded ON
  • Typical heater element resistance (varies by sensor): roughly 2–20 ohms (consult OEM spec for exact value)
  • Heater current draw: often in the range of ~0.5–6 A depending on sensor design
  • Time to heater reach operating temp: seconds to a minute after command (inferred fault if sensor does not show expected warm‑up behavior)

Diagnostic algorithm

  1. Confirm DTC P1187 and note freeze‑frame/live data. Scan for additional codes affecting O2 heaters.
  2. Inspect connectors, terminals and harnesses for both bank‑1 and bank‑2 sensor‑1 locations and common power/ground junctions. Repair visible damage.
  3. Check fuses and any heater power relay; replace if faulty.
  4. With ignition ON (engine OFF) measure voltage at each sensor heater power pin. There should be battery voltage or switched feed when commanded ON by a capable scan tool.
  5. Command the heater ON via a capable scan tool and monitor voltage/current. No voltage or no current indicates open circuit; voltage present but no current or very high resistance indicates bad heater element.
  6. Measure heater element resistance at the sensor (unplug connector). Compare to OEM spec. Very high/OL or short to ground indicates failed element.
  7. Check ground continuity from sensor connector to battery negative/chassis and to ECM ground. Repair poor ground.
  8. If both sensors lose heater feed, trace the common power feed and grounds back toward fuse/relay and ECM; repair open or short circuits.
  9. If wiring/power/ground are good but heater still fails, replace the affected O2 sensor(s). After repairs, clear codes and perform driving cycle to allow HEGO heater monitor to verify repair.
  10. If fault persists and wiring and replacement sensors are good, suspect ECM heater driver failure and verify with manufacturer‑level diagnostics before ECM replacement.

Likely causes

  • Blown fuse or single common power feed open (most likely when both banks affected)
  • Poor ground or corroded connector at sensor harness or grounding point
  • Damaged wiring harness (heat/chafe) near exhaust or manifolds
  • Failed heater element in one or both upstream O2 sensors (possible on aged sensors)
  • Faulty PCM heater driver (less common)

Fault status

⚠️ Status
ECM detected that upstream oxygen sensor heaters (Bank 1 and Bank 2, Sensor 1) are not reaching expected operating temperature when commanded. Indicates heater circuit failure, wiring/power/ground issue, or failed sensor heater elements.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

P0135 P0141 P0155 P0161 P2195
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