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Home / DTC / P1185 — Engine Oil Temperature Circuit

P1185 — Engine Oil Temperature Circuit

Detailed page for trouble code P1185.

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P1185

CHEVROLET P — Powertrain

Engine Oil Temperature Circuit

Brand: CHEVROLET
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Faulty/failed engine oil temperature (EOT) sensor/sender
  • Open, shorted, or high-resistance wiring in the sensor circuit
  • Poor/ corroded connector or pin at sensor or PCM
  • Low oil level or oil not contacting sensor
  • Contaminated sensor (covered in sludge/oil deposits)
  • PCM input circuit fault or internal PCM failure

Symptoms

  • Malfunction Indicator Lamp (MIL) illuminated
  • Incorrect oil temperature reading on scan tool or instrument panel
  • Cold/warm up drivability issues (longer/shorter warm-up, altered fuel trims)
  • Cooling fan or engine control behaviors based on wrong temperature inputs
  • Possible stored or intermittent drivability complaints if PCM uses oil temp for controls

What to check

  • Retrieve DTC(s) and freeze frame data with a capable scan tool; note conditions when code set
  • Check engine oil level and condition; correct low oil before further testing
  • Visually inspect sensor, harness and connectors for damage, contamination, corrosion or pin push-out
  • Backprobe sensor connector and check for reference voltage and signal continuity to PCM
  • Measure sensor resistance and compare to service specifications (or observe signal voltage while warming engine)
  • Wiggle harness and connectors while watching live data to look for intermittent faults

Signal parameters

  • Common sensor type: temperature-dependent thermistor (resistance changes with oil temperature)
  • Behavior: resistance typically decreases as temperature rises (NTC); signal voltage varies accordingly
  • Typical signal voltage range (approximate): ~0.5–4.5 V depending on design and temperature
  • Resistance ranges vary by design — expect values from a few hundred ohms to several kiloohms across cold-to-hot
  • Verify exact voltage/resistance specifications from the Chevrolet service manual for the specific engine

Diagnostic algorithm

  1. Connect scan tool, record DTC(s) and freeze frame data. Note engine temp, oil temp reported, and conditions when fault occurred.
  2. Check engine oil level and top to specification if low. Clear codes and re-test if low oil was corrected.
  3. With ignition OFF, perform visual inspection of EOT sensor, harness, and connectors for damage, corrosion or oil contamination. Repair as needed.
  4. With harness accessible, backprobe the sensor connector. With ignition ON (engine OFF), verify reference voltage or pull-up to ECM and low reference/ground presence per service manual.
  5. Measure sensor resistance at ambient and while warming engine. Compare readings to factory specifications. Replace sensor if out of range.
  6. Check continuity between sensor signal and PCM pin. Also check for short to battery voltage or to ground. Repair wiring faults as required.
  7. Perform wiggle/tug testing on harness and connectors while watching live data for intermittent changes. Repair harness or secure routing to eliminate chafe.
  8. After repairs, clear codes and road/test. If code returns and wiring/sensor confirmed good, perform PCM tests or consult dealer-level diagnostics for PCM replacement criteria.
  9. Safety note: avoid prolonged cranking or running without correct oil level; follow vehicle-specific service procedures.

Likely causes

  • Damaged harness or chafed wire to the oil temperature sensor
  • Corroded or loose connector at sensor or PCM
  • Failed oil temperature sensor
  • Sensor not submerged due to low oil level or wrong installation
  • Intermittent connection (water intrusion, vibration)
  • PCM fault (less common) after other causes eliminated

Fault status

⚠️ Status
Fault in engine oil temperature sensor circuit detected. PCM sees an invalid or out-of-range oil temperature signal which may affect engine control. Further electrical and sensor checks recommended.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

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369

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