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P1185

Engine Oil Temperature Circuit.

  • Oldsmobile
  • Powertrain
  • Manufacturer code
  • Low severity

How this code is built

P
SystemPowertrain
1
Defined byThe manufacturer
1
AreaFuel and air metering
85
FaultThe specific fault in that area

What it means

P1185 on an Oldsmobile means the engine control module has found a fault in the engine oil temperature sensor circuit. The module saw a signal voltage outside the range expected for the sensor, or a reading that did not make sense compared with other temperature data. This points to the sensor, its wiring or connector, or the module's reference and ground feeds.

Symptoms

  • Check engine light on
  • Oil temperature reading missing, stuck or implausible on a scan tool
  • Possible oil life monitor or oil temperature related features behaving oddly
  • Occasional change in idle or shift behaviour on models that use oil temperature as a correction input
  • No obvious drivability problem in many cases

Possible causes

  • Faulty engine oil temperature sensor (internal open or short, or drifted reading)likely
  • Damaged, chafed or corroded wiring between the sensor and the engine control modulelikely
  • Loose, corroded or contaminated sensor connector, including oil ingress into the pluglikely
  • Poor sensor ground or reference voltage supply fault shared with other sensorspossible
  • Oil leak or oil contamination affecting the sensor or its connectorpossible
  • Internal fault in the engine control modulerare

How to diagnose

  1. Read the stored code and freeze frame data, and note whether any other temperature sensor codes are present.
  2. Compare the live oil temperature reading with coolant temperature on a cold engine; they should be close after a long soak.
  3. Inspect the sensor, connector and wiring for damage, oil contamination, corrosion, chafing or heat damage. The sensor location depends on the engine, so check the service information for your model.
  4. Unplug the sensor and check the live reading: a reading that goes to the extreme end of the range suggests the circuit is intact up to the sensor.
  5. Measure the sensor resistance and compare it with the manufacturer's temperature-to-resistance specification for your engine.
  6. Check the reference voltage and ground at the sensor connector with the ignition on.
  7. Test the wiring for continuity and for shorts to ground or voltage between the sensor plug and the control module connector.
  8. Clear the code and road test to confirm whether it returns and whether the reading now behaves sensibly.

How to fix

  • Replace the engine oil temperature sensor if its resistance or reading is out of specification.
  • Repair or replace damaged wiring and ensure the repair is properly sealed and routed away from heat and abrasion.
  • Clean, reseat or replace a corroded or oil-soaked connector or terminals.
  • Repair the ground or reference voltage fault if found.
  • Fix any oil leak that is contaminating the connector or harness.
  • Have the engine control module checked or replaced only after all wiring and sensor faults are ruled out.

Can I keep driving?

Low severity

The car can normally be driven while you arrange a repair, as the fault usually has little effect on drivability. Do not ignore it for long, and stop if the oil pressure warning light comes on or the engine runs roughly.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.

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