Engine

P0197 — Engine Oil Temperature Sensor Circuit Low Input

Severity: low Safe to drive

What P0197 means

The PCM feeds a 5-volt reference to the oil temperature sensor and reads the returning voltage to work out how hot the oil is. P0197 sets when that signal voltage falls below the expected range. The cause is usually a failed sensor or a short to ground in the wiring.

Symptoms

  • Check Engine Light on
  • Oil temperature gauge reads oddly low or jumps around
  • Rough idle in some cases
  • Possible drop in fuel economy
  • Reduced power or protective strategies on some vehicles
  • Occasional hard cold starts

Possible causes

  1. Failed oil temperature sensor
  2. Signal wire shorted to ground
  3. Damaged or chafed wiring harness
  4. Corroded or damaged sensor connector
  5. Oil or moisture inside the connector
  6. PCM input circuit fault (uncommon)

How to diagnose

  1. Scan for codes and review freeze frame data, then clear the code and see if it returns
  2. Compare oil temperature with coolant temperature on a cold engine in live data; they should be close
  3. Inspect the sensor connector and harness for oil, corrosion and rubbed-through wires
  4. Unplug the sensor and watch the reading change; check the wiring diagram to interpret the result for your sensor
  5. Check for 5-volt reference at the connector
  6. Test the signal wire for a short to ground
  7. Measure sensor resistance and compare it with the spec for your model
  8. If wiring and sensor are good, test the PCM

Common fixes

  • Replace the oil temperature sensor
  • Repair or replace the damaged wiring harness
  • Clean or replace the connector
  • Reflash or replace the PCM if confirmed faulty

Questions and answers

What does P0197 mean?

The PCM is getting a too-low voltage signal from the engine oil temperature sensor. A bad sensor or a short to ground in the wiring is the most common cause.

Can I drive with code P0197?

Usually yes, for a short time. The oil temperature reading is unreliable, so overheating could go unnoticed. Have it checked soon.

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.