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Home / DTC / P1115 — Engine Coolant Temperature (ECT) Sensor Circuit Intermittent High Voltage IAT B Circuit High Input

P1115 — Engine Coolant Temperature (ECT) Sensor Circuit Intermittent High Voltage IAT B Circuit High Input

Detailed page for trouble code P1115.

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P1115

LINCOLN P — Powertrain

Engine Coolant Temperature (ECT) Sensor Circuit Intermittent High Voltage IAT B Circuit High Input

Brand: LINCOLN
Type: P — Powertrain
Views: UK: 41 EN: 84 RU: 57
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Page language: EN

Causes

  • Damaged or corroded sensor connector or terminals
  • Open, short or intermittent wiring to sensor (short to battery voltage)
  • Faulty ECT sensor or IAT B sensor
  • Poor or missing sensor ground or reference voltage
  • PCM internal fault (less common)
  • Contamination or coolant/oil ingress on the sensor

Symptoms

  • Check Engine Light (MIL) on, DTC P1115 stored
  • Incorrect coolant temperature reading on dash or erratic gauge
  • Poor idle, hard starting, or running rich/lean depending on PCM strategy
  • Reduced engine performance or limp-in mode in some cases
  • Possible cooling fan or heater control anomalies

What to check

  • Read and record freeze frame and DTC freeze data; note conditions when fault set
  • Check live data: monitor ECT and IAT B sensor voltages and temperatures while key on and engine running
  • Visually inspect sensor connectors and wiring for damage, corrosion, pin push-out, or water ingress
  • Perform a wiggle test on harness/connectors while watching live data for intermittent changes
  • Measure reference 5V (or manufacturer-specified) supply at sensor connector with key ON
  • Measure sensor ground continuity back to chassis/PCM ground

Signal parameters

  • Reference supply: typically ~5.0 V (verify with factory spec)
  • Typical sensor signal range: approx. 0.1–4.9 V depending on temperature (cold = higher voltage, hot = lower voltage)
  • At normal operating coolant temperature expect a lower signal (commonly ~0.3–1.5 V); cold engine often shows ~3.0–4.5 V
  • Any steady reading near battery voltage (≈12 V) indicates a short to B+; readings that jump to high value intermittently indicate intermittent short or poor ground
  • Sensor resistance varies by engine — consult factory chart before comparing resistance values

Diagnostic algorithm

  1. Retrieve codes and freeze frame; note ambient/engine temps and voltage conditions when set.
  2. Inspect ECT and IAT B connectors for corrosion, bent pins, or water ingress; repair or replace damaged connectors.
  3. Backprobe sensor connector and check reference voltage with key ON; if reference voltage is missing or high, trace to PCM/fuse.
  4. With key ON and engine off, measure signal voltage at sensor and compare to expected cold values. Warm engine and re-check signal at operating temp.
  5. Check continuity from sensor ground to chassis/PCM ground; repair any high resistance or intermittent ground.
  6. Perform a wiggle test on harness and connectors while watching live data for intermittent jumps to high voltage; repair or re-route wiring as needed.
  7. If wiring and connectors test good, disconnect sensor and measure sensor resistance across its terminals at various temperatures and compare to factory specification; replace sensor if out of spec.
  8. Repair any short to battery voltage or open circuits found. After repairs clear codes, perform a drive cycle and verify the fault does not return.
  9. If all wiring, grounds and sensors test within specifications and the fault persists, consider PCM/ECM diagnosis or replacement following manufacturer procedures.

Likely causes

  • Loose/corroded connector at ECT or IAT B sensor
  • Wiring chafed and shorted to constant 12V
  • Failed temperature sensor element (high resistance or open at temp)
  • Intermittent ground connection at engine harness or PCM
  • Previous repair disturbed wiring harness near sensor

Fault status

⚠️ Status
P1115 — ECT Sensor Circuit Intermittent High Voltage / IAT B Circuit High Input. PCM detected sensor circuit voltage above expected range or intermittent high signal; inspect sensors, wiring, grounds, and reference voltage.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5 - 2.0 hours

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