P0198Generic code

P0198 Code: Engine Oil Temperature Sensor High

The P0198 code means the engine oil temperature sensor signal is above its maximum value. On a thermistor, that is an impossibly cold reading, almost always from an open circuit or a loose connector.

Severity
Medium
Can I keep driving?
Yes, but with caution
Estimated cost
$30 to $250
Difficulty
Medium
System
Air and Fuel
Applies to
All OBD2 vehicles

Updated Reviewed by Renzo Chacca

On this page

What the P0198 code means

The engine oil temperature sensor sits in the engine block, in the oil pan, in the oil filter housing or built into the oil level or oil pressure sensor. The computer uses it to protect the engine, to adjust variable valve timing control and, on some vehicles, to calculate the oil change interval.

The sensor is an NTC thermistor powered with 5 V by the computer. A signal close to 5 V is equivalent to an impossibly low temperature (the scan tool usually shows -40 °C, or -40 °F), and that almost always means an open circuit: a loose connector, a cut wire, an interrupted sensor ground or a sensor open inside. While the fault lasts, the computer believes the oil is cold. It adjusts variable valve timing and service intervals incorrectly.

Keep in mind that the P0198 code points to the circuit where the computer saw the problem, not necessarily the part that failed. Check the wiring before you replace the sensor. The diagnosis steps below walk you through the tests one by one.

P0198 code symptoms

  • Check engine light on steadily.
  • The computer believes the oil is cold and adjusts variable valve timing and service intervals incorrectly.
  • In many cases you notice nothing while driving, just the light.
  • Possible companion codes from the same sensor (low, high or intermittent signal).

Likely causes of the P0198 code

  1. Connector unplugged or not fully seated, for example after a repair or after changing the air filter.
  2. Signal or ground wire cut inside the insulation or at the connector itself.
  3. Corroded or open connector pins that no longer make contact.
  4. Sensor open inside, with infinite resistance.
  5. Additional check: A low oil level or badly degraded oil can cause real high readings. Check the oil before you blame the sensor.

How to diagnose the P0198 code step by step

  1. Read the sensor in live data and compare it with what you expect: with a cold engine it should match the coolant and air temperature. Once running, the oil warms up a little more slowly than the coolant and ends up between 90 and 120 °C (194 to 248 °F).
  2. Inspect the connector. Unplug it, look for green, backed-out or oily pins, and push it back on firmly.
  3. With the key on and the sensor unplugged, measure the reference at the connector. You should see about 5 V between the signal and ground.
  4. Jumper test. With the sensor unplugged, the scan tool should show about -40 °C (-40 °F). When you join the two connector pins with a jumper wire, it should jump to more than 120 °C (248 °F). If it does, the wiring is good and the problem is the sensor.
  5. Measure the sensor resistance and compare it with the technical data below at the current temperature.
  6. Do a wiggle test. With the engine running, move the harness and the connector while you watch live data. A jump gives away the point of the fault.
  7. Check the continuity of each wire between the sensor connector and the computer connector with the key off.

How to fix the P0198 code

  • If the connector was loose or corroded, clean it with contact cleaner and secure it.
  • If the jumper test shows the wiring is good, replace the sensor.
  • If the signal is missing at the connector, repair the open wire by soldering and insulating it with heat shrink tubing.
  • Use an original-quality or equivalent sensor: cheap generic sensors often have different response curves.
  • Clear the codes, drive a full cycle and check in live data that the reading makes sense.

Technical reference data

  • NTC thermistor with 2 wires and a 5 V reference (on some engines combined with the oil level sensor).
  • Approximate resistance: 2,000 to 3,000 ohms at 20 °C (68 °F) and 150 to 250 ohms at 100 °C (212 °F).
  • Normal oil temperature when running: 90 to 120 °C (194 to 248 °F).
  • Approximate values: check the manufacturer data for your engine.

Brand-specific notes

Where the sensor lives depends on the engine, so look up its location before you order parts. That matters if you are chasing the P0198 code and the wiring tests out fine.

P0198 on Volkswagen

On many engines the temperature sensor is combined with the oil level sensor under the oil pan, and the whole assembly is replaced.

P0198 on Audi

On many engines the temperature sensor is combined with the oil level sensor under the oil pan, and the whole assembly is replaced.

P0198 on BMW

On many engines the temperature sensor is combined with the oil level sensor under the oil pan, and the whole assembly is replaced.

P0198 on Mercedes

On many engines the temperature sensor is combined with the oil level sensor under the oil pan, and the whole assembly is replaced.

P0198 on GM

The sensor is usually located near the oil filter.

Frequently asked questions about P0198

What does the P0198 code mean?
It means the oil temperature sensor signal is above its maximum value. On a thermistor, that is an impossibly cold reading, almost always from an open circuit or a loose connector.
Can I drive with a P0198 code?
With caution and only for a short time. The engine runs on substitute values, may lose power or burn more fuel and, in some cases, may go into limp mode.
Does the P0198 code always mean replacing the oil temperature sensor?
No. In most cases the fault is in the connector or the wiring. Do the supply, ground and continuity tests first.
What is the difference between a low signal and a high signal?
On a thermistor, a low signal means an impossibly high temperature (a short), and a high signal means an impossibly low temperature (an open circuit).
How much does it cost to fix P0198?
Roughly $30 to $250. The cheapest fix is repairing a connector and the most expensive is replacing the sensor with labor. It varies by shop and region.
Will a P0198 code clear itself?
Only if the fault stops happening. An open wire or a corroded connector will bring the code back, so clearing it without a repair only hides it for a while.
What is the most common cause of P0198?
A connector that is unplugged or not fully seated, often after other work on the engine. Check it first.

Related codes

Questions about the P0198 code

There are no questions about this code yet. Tell us about your case: vehicle, symptoms and what you have already checked.