Engine

P0199 — Engine Oil Temperature Sensor A Circuit Intermittent/Erratic

Severity: medium Drive with care, to a shop

What P0199 means

The engine control module reads a voltage from the oil temperature sensor, whose resistance changes as the oil heats up. P0199 is set when that signal jumps, drops out or doesn't match how the engine is warming up. It usually points to a poor connection in the circuit, less often a failing sensor or control module.

Symptoms

  • Check Engine Light on
  • Oil temperature reading jumps or drops out
  • Rough idle
  • Reduced power or limp mode
  • Cooling fan running unexpectedly
  • Sometimes no symptoms besides the code

Possible causes

  1. Failing engine oil temperature sensor
  2. Corroded or loose connector terminals
  3. Damaged, chafed or broken wiring
  4. Short or open to ground or power in the sensor circuit
  5. Oil or moisture in the connector
  6. Faulty PCM (rare)

How to diagnose

  1. Scan for other codes and review freeze frame data
  2. Compare oil temperature to coolant temperature on a cold engine; they should be close
  3. Inspect the sensor connector and harness for chafing, oil and corrosion
  4. Wiggle the harness and connector with the engine running while watching live data
  5. Check reference voltage and ground at the connector with a multimeter
  6. Measure sensor resistance and compare to the manufacturer spec
  7. Test the wires to the PCM for opens and shorts
  8. If everything checks out, test the PCM

Common fixes

  • Clean and repair connector terminals
  • Repair or replace damaged wiring
  • Replace the oil temperature sensor
  • Reprogram or replace the PCM (last resort)

Questions and answers

Can I drive with P0199?

For a short time, yes, provided there is no overheating or low oil pressure. Don't put off diagnosis, since the engine is running on unreliable data.

What most often causes P0199?

Most often a poor connection or damaged wiring, followed by the sensor itself. The PCM is rarely at fault.

How do I clear P0199?

A scan tool can clear it, but the code will return unless the cause is fixed. Check the connector, wiring and sensor first.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.